BIOLOGY 101L
LABORATORY MANUAL
M. Shapiro and J. W. Floyd
Leeward Community College
Fall 2002
Student’s Name:
Table of Contents:
Introduction to Biology 101 Laboratory
Lab 1 – Asking Scientific Questions
Lab 2 – Biological Macromolecules
Lab 3 – Cells, Microscopes, and Domains of Life
Lab 4 – Cellular Transport: Brownian Motion, Diffusion, and Osmosis
Lab 5 – Cellular Respiration: Alcoholic Fermentation
Lab 6 – Photosynthesis in Coleus Leaves
Lab 7 – Nuclear Division: Mitosis and Meiosis
Lab 8 – Genetics and Inheritance
Lab 9 – Seed Germination Experiment
Lab 10 – Microevolution and the Hardy-Weinberg Equilibrium
Lab 11 – Macroevolution
Lab 12 – Plant Diversity
Lab 13 – Animal Taxonomy
Lab 14 – Honolulu Zoo
Lab 15 – Population Ecology: Population Density and Survivorship Curves
Lab 16 – Community and Ecosystem Ecology: Foraging Strategies, Food Webs, and Energy
Flow
Lab 17 – Human Health and Physiology
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Introduction to Biology 101L
About This Course
This is a one-credit laboratory science course designed to accompany the Biology 101 lecture
course. The laboratory meets once a week for 3 hours. Note that this ratio of one credit for a 3hour weekly laboratory, with additional assignments to be completed outside the lab, is a normal
academic standard. If taken for a grade, BIO l0lL can fulfill the core course requirement for the
College of Arts and Sciences curriculum.
The course uses a “hands-on,” experiential approach with a two-fold purpose: (1) to acquaint you
with the nature of scientific methodology, and (2) to illustrate and reinforce some of the biological concepts discussed in the lecture course.
Structure of the Lab & Grades
You should carefully read each laboratory exercise BEFORE each lab. In addition, you should
review the text and lecture notes for information related to the laboratory topic. A short
introduction to each laboratory exercise will be given by your Instructor at the beginning of the
lab period. This introduction is intended to provide background information not available to you
in your lab manual or text and to demonstrate techniques that may be unfamiliar to you. Upon
arrival at the lab, you should know what is to be accomplished that day and what is required of
you as a follow-up to the in-lab work, i.e., questions to be answered and handed in or
assignments for future labs.
The laboratories in this manual are intended to complement the lectures in BIO 101. Our emphasis here differs somewhat from that in lecture. While we are still concerned with the “facts”
in lab, we are more often concerned with the scientific method. For example, during lecture you
will be taught about the scientific method, but in the lab you will be guided through the actual
design, implementation, and report of a scientific experiment. These two approaches
complement each other and, taken together, will provide both a conceptual and experimental
background in the mechanism by which science proceeds.
Another emphasis in the lab is technique. It’s not enough to know the “facts.” You also need to
know how to obtain facts. In addition to hypothesis formulation and experimental design, you
will learn the proper use and care of certain scientific instruments. Adherence to the scientific
method lies at the core of science. Improper technique often results in biased data which, ultimately, impede science rather than advance it.
Another emphasis in lab is to get you to think. Too often students feel that they can do well in a
course by simply memorizing the materials. In the lab we ask you to make observations and to
think critically about the way the observations have been made and their implications. Your Instructor is here to help you learn as much as you can about modern biology and its implications
for your life. We wish you success and enjoyment.
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Materials Needed
Most materials will be provided to you in lab. You may also find it helpful to have a metric
ruler, graph paper, a calculator, and a set of colored pencils.
Attendance
REGULAR ATTENDANCE IS REQUIRED. Only under exceptional circumstances will there
be an opportunity for you to come into the laboratory at times other than your scheduled period.
You should therefore be prepared to come to lab and to do all your work during your scheduled
lab period. If circumstances dictate that you cannot attend your normal lab session, you MUST
notify your Instructor and present any written documentation (e.g., doctor’s note). Your
Instructor will attempt to make an arrangement for you to attend another lab during the same
week. Students are not allowed to just show up at another lab session without prior arrangement.
If special circumstances (e.g., prolonged illness, bereavement) prevent you from doing lab work
during the week it is scheduled, you must document the reason for your absence (e.g., doctor’s
note) to avoid receiving a grade of “zero” for that week’s work. Consult with your Instructor if
special circumstances arise.
Grading
Attendance and participation is critical for you to get anything out of a laboratory course.
Participation is part of your grade for this course, therefore your grade may be reduced if you
miss a lab during the semester. If you miss more than one lab, you may not be able to receive a
passing grade for the course. Some labs may be able to be made up during other lab periods.
Contact your Instructor as soon as possible to make arrangements if you are going to miss a lab.
Your Instructor may direct you to turn in assignments or written scientific report papers from
certain labs. You may also be given a Lab Practical Quiz the next week after some labs. Refer
to the syllabus from your Instructor as to exactly what assignments and quizzes will be expected.
Your laboratory grades will be combined with your lecture grades at the end of the semester to
determine your overall grade for the course.
Scientific Report Paper
You Instructor may direct you to write a scientific report paper on one of the experiments we
conduct in lab. This report will be written similar to research papers that appear in scientific
journals. You will also do some library research about the topic to include in your report. More
information will be given at the appropriate lab.
Lab Practical Quizzes
You may have one or more Lab Practical quizzes during Bio 101L. These quizzes will be
largely “practical” in nature. For example, you may be asked to demonstrate use of a certain
feature on a microscope, design a simple experiment on a designated topic, or identify a given
phase of mitosis on a slide with many dividing cells. Such “practicals” demonstrate your ability
to actually apply knowledge, rather than simply regurgitate memorized facts. Refer to your
syllabus for when the quizzes will be given.
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Academic Conduct
Any student caught cheating or plagiarizing, will, at a minimum, receive a grade of “zero” on the
falsified work, and have a written warning filed with the Dean of Students. According to the Student Conduct Code of the University of Hawaii at Manoa:
“Plagiarism includes but is not limited to submitting, in fulfillment of an academic requirement,
any work that has been copied in whole or in part from another individual’s work without attributing that borrowed portion to the individual; neglecting to identify as a quotation another’s
idea and particular phrasing that was not assimilated into the student’s language and style or
paraphrasing a passage so that the reader is misled as to the source; submitting the same written
or artistic material in more than one course without obtaining authorization from the instructors
involved; or “dry-labbing”, which includes obtaining and using experimental data and laboratory
write-ups from other sections of a course or from previous terms.”
“Cheating includes but is not limited to giving or receiving unauthorized assistance during an
examination; obtaining unauthorized information about an examination before it is given; submitting another’s work as one’s own; using prohibited sources of information during an examination; fabricating or falsifying data in experiments and other research; altering the record of any
grade; altering answers after an examination has been submitted; falsifying any official University record; or misrepresenting of facts in order to obtain exemptions from course requirements.”
Laboratory Safety Regulations
The laboratory exercises have been designed with safety in mind. You have responsibilities, too.
Foremost, use common sense, keep the lab clean, and be familiar with safety procedures.
Identify the available safety equipment, including the first aid kit and fire extinguisher. Return
equipment & supplies to their proper places after using them.
•
The best clothing for labs should cover most of the body. Closed-toed shoes will protect
feet, and glasses can protect the eyes.
•
Do not place books, purses and notebooks on lab surfaces when starting lab activities. Put
them out of the way, under tables, or in drawers of the lab tables.
•
Place the cords of electrical equipment, such as hot plates and microscopes, out of reach to
prevent them from being tugged or pulled off the tables.
•
Assume any chemical that you handle is hazardous: if spilled, contact instructor for cleanup
instructions. If some falls on your skin, immediately wash with water. If some squirts into your
eye, use eye-wash apparatus for flushing the eye.
•
Do not eat, drink or apply make-up in the lab, except under special situations determined
by the instructor. Do not drink from lab glassware, or taste or smell chemicals.
•
Do not use damaged glassware. If glassware is breaks, immediately contact instructor for
clean-up and proper disposal. Do not put it into the regular trash cans, but into the special
broken glass box.
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•
Use caution when heating chemicals with hot plates. Do not pick up hot glassware except
by protective mitts. Avoid spilling or splashing hot liquids.
•
•
Obtain help with pouring or accessing chemicals in large containers.
Report all accidents or hazards immediately.
•
Know where safety kit is in the lab, where lab manager’s office is, where phones are to get
emergency help. Call 611 at Leeward for emergencies.
•
Follow directions for clean up of lab; return chemicals and supplies to original places, wash
glassware at sinks with detergent and leave to dry and wipe down table tops to remove any
chemical spills.
•
If you have chronic or defined respiratory problems, of known or possible allergies to plant
or chemical materials, please inform instructor.
• Dispose of waste in proper receptacles. Glass has its own container. Clean up spills immediately.
• Clean your workspace area at your table before leaving! Cleaning materials are located near
the sink.
•
Emergency evacuation procedures: When the fire alarm sounds, prepare to leave the room
and building immediately. The instructor should make sure everyone is ready to leave.
Anyone with hearing problems or other disabilities will be helped to leave the room and
building. The instructor will be the last one to leave. If conditions are safe to do so, reassemble in the parking lot, so your Instructor can be sure everyone is accounted for and is
safely away from the building.
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UNIVERSITY OF HAWAII - LEEWARD COMMUNITY COLLEGE
Assumption of Risk and Release for Laboratory Activities
Name of Course/Activity: ____________________________
Period: ___________________________________________
Name of Student/Participant: (print) ________________________________________
1 have read and fully understand the written safety and other rules and precautions that are a part
of the requirements for my participation in the above referenced course/activity, as well as those
explained to me by me instructor(s), and I agree to strictly observe them; and
I hereby accept full responsibility for the indemnify, release and discharge the University of
Hawaii, its officers, agents, and employees from any and all claims of actions for property
damage, and/or personal injury which may result from my failure to abide by these safety rules
and precautions, or from any inherent risks in said course/activity.
____________________________________
(signed by Student/Participant )
_________
Date
____________________________________
Co-signature of parent of guardian
if Student/Participant is under 18 years of age
_________
Date
University of Hawaii - Leeward
96-045 Ala Ike
Pearl City, HI 96782
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Lab 1: Asking Scientific Questions
Introduction
Science has three roles in our society: First, science is a body of accumulated knowledge
regarding our physical universe and its inhabitants.
Second, science is a way of thinking about this universe that involves certain fundamental assumptions or scientific principles such as natural causality, uniformity of natural laws, and common objective perception. Natural causality means that events in our universe are the result of
preceding natural causes (as opposed to the supernatural). The principle of the uniformity of
natural laws states that the basic laws of physics and chemistry (gravity, speed of light, radioactivity, etc.) that govern the universe do not change with time or place. Common objective perception is the assumption that all humans, using their basic senses objectively, can make the
same observations and gain the same understanding of natural events.
Third, science is a process by which we investigate and understand the universe. This process,
known as the “scientific method,” begins with asking questions about observations made regarding the natural universe. However, such questions in science must be properly formulated if they
are to lead to practical experiments and objective scientific answers. Many questions will be
posed and answered in this class, but you are encouraged to expand on these, to pose questions
of your own, and to strive to answer them. Become inquisitive and question the world you are
experiencing. If you do this, rather than passively accepting information provided by others, you
will benefit much more from today’s lab, this class, and life in general.
It is important to ask questions based upon observations. In general, questions that ask “How?”
are preferred over questions that ask “Why?” The former lead to hypotheses that are experimentally testable, whereas the latter may lead to answers that imply higher purpose and design,
which are outside the realm of science. A hypothesis is a working explanation that leads to a
testable prediction. Good scientific hypotheses generalize from specific observations. This
process occurs through inductive reasoning. For example, here is an observation: “Every
morning birds land on my lawn and begin feeding. They stop feeding and fly away in the
afternoon.” Although you may ask, “Will they repeat this behavior tomorrow?”, a better question
might be “What are the environmental factors that cause these birds to interrupt their feeding and
leave?” Note that the first question, although it leads to a testable hypothesis, deals with a
specific expectation, rather than a generalization. Hypotheses arc often written as an “If/then”
statement. For example: If the birds have fed for 4 hours, then they will leave. This could be
tested with starting a timer as soon as they arrive and start eating.
Good scientific questioning also takes into consideration the information already accumulated
and the technological capabilities of the scientists. It is not very practical to ask, “What is the
nature of the universe?” Although answering this question is the ultimate aim of science, this
question is too open-ended and beyond any one scientist’s technical capabilities.
Finally, good scientific questioning goes beyond the obvious answers. Asking “What color are
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butterflies?” and hypothesizing ‘yellow”, is not very useful or interesting. A better question
might be “What is the adaptive function of their color?”
Approaches to Problem Solving: the Scientific Method
Questioning in biological science may lead to one of two problem-solving approaches: the descriptive approach and the experimental approach. You will encounter examples of both of
these investigative approaches throughout this class.
The descriptive or discovery approach stems from a question about attributes that are typical
and that may be measured to give an answer, such as, how many are there? or where are they
found? These kinds of questions may be answered by making more observations. For example,
questions about the population density of sea cucumbers on the reef flat may be answered simply
by going out and counting sea cucumbers. Data are gathered, results are summarized and
analyzed, and conclusions are made.
The experimental or hypothesis-driven approach is used to answer questions that involve
manipulation of environ-mental variables, such as, what will happen to organism A if condition
X is modified in a deliberate and controlled manner? For example, while counting sea
cucumbers, you may notice that most are found under rock ledges. You formulate the question:
“What are the environmental factors that determine the sea cucumber distribution pattern?” This
is the problem that you desire to solve or to understand better. You then develop an hypothesis, a
preliminary or tentative answer based on the information available at the time. One possible
hypothesis might be that sea cucumbers avoid the bright light and seek the shade under the rock
ledges. This hypothesis might lead to the prediction that given a choice of brightly sunlit or
shaded environments, a sea cucumber will move and remain in a shaded environment.
Now you devise an experimental procedure to test the validity of your hypothesis and its predictions. Each experiment that you design has two components, the treatment and the control. The
treatment is the environmental variable that you manipulate. The control is the parallel test that is
carried out to provide a standard against which an experimental result can be evaluated. The
control has identical experimental conditions except for your one varied factor, or treatment. You
carry out the experimental steps and get experimental results. Then conclusions can be drawn
which either support or reject your hypothesis. These conclusions will provide at least a partial
answer to your initial question, and probably stimulate new questions.
Practice in Problem Solving
In this exercise, get to know your lab partners and work in pairs to examine the structure of
questions, to consider how questions in biology are answered, to make observations and to ask
questions that lead to a testable hypothesis.
For the list of questions below, mark with an E those that you think could be answered with the
experimental approach, and mark with a D those that could be answered with the descriptive
approach. Some may be both.
_____ What do tiger sharks eat?
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_____ Is the earth’s atmosphere mostly oxygen?
_____ Does a clam’s heartbeat increase with increasing water temperature?
_____ How many species of birds inhabit the Leeward campus?
_____ Do bees prefer certain flowers?
_____ Is it safe for humans to eat crabs from the Ala Wai Canal?
_____ Is there extraterrestrial life?
Select one of the above questions marked with an E. Develop a hypothesis and devise a brief experimental procedure. What sort of data will be collected during the experiment? What will
be the controls for the experiment?
Select one of the questions marked with a D. Again develop a procedure to answer the question.
Summarizing Data
Any time we take measurements in science, we need a way to summarize these data (note: this
word is plural; one single measurement value is a datum). We also notice that there is a lot of
variability caused by naturally occurring variation and our experimental treatments. We need
methods to allow us to understand this variability and to compare different sets of data. Statistics
is defined as the scientific study of numerical data based on variation in nature. Statistical analysis allows us to summarize our data into a readily understandable form.
Biologists generally study populations of organisms; that is, all the individuals of a given species
found in a circumscribed area at a given time. It is often impossible (and impractical) to study
every organism in the population. Therefore, scientists usually make observations on some
feasible number of organisms. They use this sample of the population to provide an estimate of
what the whole population is really like. In a general sense, the larger the sample, the more accu-
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rate the estimate becomes. This is because there is less likelihood that a few chance, deviant
measurements will bias (unduly influence) our estimate. Sampling should be done randomly to
help reduce bias in the results. There is always some error or inaccuracy in scientific
measurements. Scientists try to identify and quantify the sources of error. One source of error is
based on the precision, or lack of it, in our measurements. For instance, when measuring time, a
watch may be fast or slow. Also if you measure to the nearest minute, your measurements wont
be as precise as measuring to the nearest second. Bias can also be a source of error in science.
Scientists are humans with opinions, prejudices, and desires for success. Much human bias is
unconscious. Scientific questions, the methods used in experiments and the conclusions drawn
from results are all subject to bias. So scientists report procedures to others for criticism and
advice, and try to improve procedures and reduce bias.
The features that we measure are called variables or characters. In a study of a population of pea
seedlings, variables that we might observe include plant height, maximum leaf width, dried plant
weight, leaf color, or the number of leaves. Some variables can be measured (for example, length
and weight) and given numerical values; these are called quantitative variables. Other variables
are attributes that must be expressed qualitatively (such as color or texture). Such variables can
only be described and are termed qualitative variables. Variable in a data set may be related, or
correlated, to each other. If both variables tend to increase at the same time, then that is a
positive correlation. If one variable increases as the other decreases, then that is a negative
correlation. If there is no correlation, then the variable are said to be independent.
In this lab, you’ll learn some basic graphing and techniques for analyzing data. When you do
your seed germination experiments, you will be collecting measurements of variables. You will
need to analyze these data, too. So the techniques you will be studying here will be used in
several other situations this semester. Statistics is an important component of quantitative
research. Statistics not only allows you to quantitatively describe and compare information, but
also makes your conclusions more objective.
Descriptive Statistics
There are two basic groups of descriptive statistics: statistics of location and statistics of dispersion. Statistics of location tell us about the central tendency of the data. A familiar statistic of location is the mean or average, symbolized as x (read as x-bar). The mean of a data set is calculated by summing up all of the measurements and dividing that sum by the number of observations. Note that the mean is not necessarily the true average of the population. Remember that
you only measure a sample from the population. If the sample is large and is representative of the
population, however, then the sample mean should be a good estimate of the true population
mean. Another measure of the central tendency of a variable is the median or middle measurement in a ranked listing of the data. Equal numbers of measurements are higher and lower than
the median.
Presenting Tables
Statistical information about your data can be presented in a table, a list of values arranged in
columns and rows. A table should be able to stand alone for anyone to interpret without having
to refer to other written material, nor having to ask the researcher to explain it. Thus, every table
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should have its own descriptive title, column headings and row headings. The units for a particular variable should be indicated (usually in the headings). Any other information pertinent to the
table may be placed in a legend below the table. Look at the example below of an informationpacked table.
Table 1. The Effects of High and Low Fat Diets on the Weights and Lengths of a Group
of Rats. The high fat diet consisted of 50% fat, while the low fat diet consisted of 5% fat.
The values are the means for 100 rats.
Diet Type
Mean Weight (g)
Mean Length (cm)
--------------------------------------------------------------------------High fat
545.5
55.3
Low fat
346.7
53.2
In summary, the main parts of a table are:
1) Table #
2) Title with description
3) Column headings
4) Row headings
5) List(s) of data
6) Units of measurements
Let’s assume that you have collected the following data on 10 snakehead cowries (Cypraea
caputserpentis) from some tropical islands. A cowry is a type of marine mollusk. First you make
a data table to record your observations.
Table 2. Observations on Snakehead Cowries
shell
length
weight
sex
color
number
(mm)
(g)
--------------------------------------------------------------------------1
10.4
5.2
F
green-yellow
2
11.1
6.2
M
yellow
3
10.7
5.7
M
yellow
4
10.6
5.5
F
green
5
10.9
6.0
M
green-yellow
6
10.5
5.4
M
yellow
7
10.2
5.1
F
green
8
11.2
6.3
M
yellow
What are the quantitative variables for this data set?
What are the qualitative variables for this data set?
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Graphing
Long lists of data are often not very useful for identifying trends in the variables or for noting
significant points. The next step is to graph the data. Make a scatter graph showing how the
weight of a shell is related to its length in Figure 1. A scatter graph plots the relationship between
two variables with a single point for each subject and does not connect the points with a line).
All graphs need to be completely labeled and identified as Figure 1 or Figure 2 with a title and
description.
Weight (g)
6.5
6
5.5
5
10
10.5
11
11.5
Length (mm)
Figure 1. Length-weight relationship of snakehead cowries.
How are they correlated? (That is, is there any trend between length and weight?) Is the relationship positive or negative?
Number of individuals
Now you want to show how many shells are female and how many are male, so make a
frequency diagram (bar graph) in Figure 2. The vertical axis represents the counts or frequency
(%) of a set of categories (male or female). Note that in a frequency diagram, the horizontal axis
is always divided into categories that are equally represented by the width of the bar.
8
7
6
5
4
3
2
1
0
male
female
Sex
Figure 2. Frequency of male and female snakehead cowries.
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Exercise – Turn in pages 13-15 before you leave lab.
1. Our population is the students in this section of BIO 101 lab. The class will be divided randomly into two sample groups. Measure the following variables in centimeters on the individuals in your sample, including yourself. Fill in the table number, the table title, and the
units of measurements you used for your quantitative variables.
Table #______ Title:
Name
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
mean
right hand (cm)
head circumference (cm)
sex
Describe two possible sources of error in your measurements.
Describe any possible bias in your measurements.
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2. Make a frequency diagram of the number of males versus females. Be sure to label each axis
of the graph.
3. Make a scatter graph of right and length vs. head circumference. Use appropriate scales
which best represent your data. In other words, don’t start each axis at zero when no student has
a hand that is 0 cm in length. Be sure that whenever you draw graphs that you clearly label the
axes with the variable name and its units.
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Circle all points on your graph that have been measured from females in your sample.
What does your scatter diagram tell you about the relationship between right hand length and
head circumference? Are they independent of each other or correlated in some way?
Based on your data, what conclusions can you make about male/female differences in these variables? (Look at your circled points.)
4. Calculate the means of the variables for males and females separately. Make a table to
summarize this information. Be sure to include all the parts of a table that are pertinent to the
table you make.
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Lab 2: Biological Macromolecules
*Note - Please bring several food items to this lab that you would like to test.
Introduction
Four major classes of organic compounds, carbohydrates, proteins, lipids, and nucleic acids,
make up the bulk of living matter. In the first part of this laboratory you will conduct some
simple chemical tests to reveal the presence of characteristic functional groups for the first three
groups. The last part of the laboratory examines the fat, sugar, and salt contents of some popular
foods.
Carbohydrates
Carbohydrates comprise a wide variety of monomers, dimers, and polymers of saccharides
(sugars). No single chemical test is effective in detecting all of them. You will conduct two tests
specific for two important types of carbohydrates, simple sugars and polysaccharides.
Benedict's solution, a mixture of sodium citrate, sodium carbonate, and copper sulfate, tests for
the presence of simple sugars. When reacted with a small quantity of sugar, the blue-colored
Benedict’s solution turns green; a reaction with a large amount of sugar turns the solution redorange.
Many polysaccharides react with Lugol's reagent (iodine potassium iodide). When amylose and
amylopectin (plant starch) react with Lugol's, the solution turns to a blue-black color; glycogen
(animal starch) turns red-brown; cellulose (the major component of plant cell walls) turns violetbrown to red-brown. The color change is the result of the iodine molecule reacting with the
helical structure of the polysaccharide.
Lipids
Two important lipids are fats and oils. Chemically, the two are very similar, as both are made
from two subunits, glycerol and fatty acids. The long, nonpolar hydrocarbon “tails” of fats
make them insoluble in water (you're probably already aware of this if you like vinegar and oil
salad dressing), and this insolubility itself is a good test for the presence of fats. Another test
utilizes a lipid-soluble dye called Sudan III. Sudan III dissolves in nonpolar substances such as
fats and oils, staining them orange-red.
Proteins
Proteins are large molecules composed of many amino acids linked together by peptide bonds.
Proteins, react positively with Biuret reagent (sodium hydroxide and copper sulfate), turning
from a blue to pinkish-violet color.
Testing for the Presence of Biological Compounds
Students should work in groups of 4. Each group should turn in one copy of pages 19-20.
Part I. First, perform each test below on the “pure” foods provided for you in lab. Also run a
control for each test. (What substance should be used for the control?) Make notes on what
happens in each test to indicate a positive and negative result for each biological macromolecule.
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You will have the following “pure” compounds available for a positive reference testing: 1%
glucose (a reducing sugar), 1% egg albumin (a protein), 1% soluble plant starch (a
polysaccharide), and corn oil (a lipid).
A. Benedict's Test for Reducing Sugars
1. Add 1 mL of the test solution to a clean, dry test tube.
2. Add 1 mL of Benedict's solution to the test tube, mix well, and heat the tube in a dry bath at
95-99oC for 4-5 minutes.
3. Carefully remove the tube and allow it to cool.
4. Compare/record the resulting color.
B. Lugol's Test for Polysaccharides
1. Add 1 mL of the test solution to a clean, dry test tube.
2. Add 1-2 drops of Lugol's reagent (6 g KI, 4 g I/100 mL) to the tube and mix well.
3. Compare/record the resulting color.
C. Sudan III Test for Lipids
1. With a pencil, write the identity of the test solution on a piece of filter paper.
2. With a clean plastic bulb pipette, transfer a VERY SMALL drop of the test solution to the
filter paper. The solution will spread out very rapidly so try to just touch the pipette to the paper.
3. Allow the spot to dry completely (4-5 minutes), and then, with forceps, submerge the filter
paper in a dish of Sudan III solution (0.1% Sudan III in 95% ethanol) for exactly 1 minute.
4. Transfer the paper to a dish of distilled water for 1 minute to wash away the excess dye.
5. Compare/record the color of the spot.
D. Biuret Test for Protein
1. Add 1 mL of the test solution to a clean, dry test tube.
WARNING!! The following step uses NaOH, a STRONG alkali. Be sure to use all your
personal protective gear (lab coat, safety goggles, and gloves) when working with this
material.
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2. Add 2 drops of 40% sodium hydroxide (NaOH) to the tube and mix well by swirling the test
tube.
3. Add 2 drops of a 2% copper sulfate solution to the tube and mix well. Compare/record the
resulting color.
Part II. Now, design and conduct your own experiments to determine what biological
macromolecules are present in each of the food items you brought for testing. For best results,
the substance should be broken down into small pieces. Consult with your instructor on whether
you need to grind your food item or dissolve it in water, etc. Write down your hypothesis for
each experiment. Make a table detailing the results of your food experiments. Remember to
follow all the rules for constructing tables. Some questions to consider when you're designing
your experiment are:
1. What does a positive and a negative test look like? What substance(s) will you use for
positive and negative controls?
2. How many times should you replicate your experiment?
3. How might the concentration of your test food affect the results of a biochemical test?
Clean up
Clean your test tubes with detergent and return them (inverted to dry) to their test tube racks,
EXCEPT THOSE USED FOR FATTY SUBSTANCES. Those can be disposed of in a box
designated for glass. Return all re-useable supplies and equipment to their original location.
Thoroughly wipe off you lab table.
Experiment Design and Hypotheses:
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Results Table:
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Lab 3: Cells, Microscopes, and Domains of Life
Introduction
In 1665, the English scientist Robert Hooke used a primitive microscope that magnified objects
30 times (30X) to observe a thin slice of cork (bark from an oak tree). There he saw “a great
many little Boxes” which he called “cells”, because they reminded him of the tiny rooms, or
cells, occupied by monks. Today, powerful electron microscopes which magnify objects up to
500,000 times reveal the complex internal structure of cells. In the several centuries between
Hooke’s original discovery and today’s scientific frontiers, research by generations of scientists
has formulated and supported the basis of modern cell theory:
(1) Every living organism is made up of one or more cells.
(2) The smallest living organisms are single cells, and cells are the functional units of
multicellular organisms.
(3) All cells arise from preexisting cells.
There are two fundamentally different types of cells: prokaryotic and eukaryotic. “Karyotic”
refers to the nucleus of a cell, a membrane-enclosed sac which contains the genetic material.
“Pro” means “before” in Greek, and prokaryotic (“before a nucleus”) cells do not have an
organized nucleus surrounded by a membrane. “Eu” means “true” in Greek, and eukaryotic
(“true nucleus”) cells do have an organized nucleus enclosed by a membrane.
All cells, whether prokaryotic or eukaryotic, have at least three components: (1) a plasma
membrane which surrounds the cell and regulates the flow of materials between the cell and its
environment, (2) genetic material, and (3) cytoplasm, which consists of all the material inside
the cell membrane except the nucleus. In addition to the presence or absence of a nucleus, there
are additional important differences between prokaryotic and eukaryotic cells. Prokaryotic cells
are very small, with a relatively simple internal structure. Although the functions carried out by a
prokaryotic cell may be quite complex, these functions are not associated with discrete,
membrane-bound structures, or organelles, inside the cell. In contrast, eukaryotic cells contain a
variety of membrane-enclosed organelles that lend structural and functional organization to the
cell. Eukaryotic cells are also larger than prokaryotic cells.
The astonishing diversity of life on Earth (at present, around 1.5 million species have been
named) is presently classified by biologists into three domains: Archaea, Bacteria, and
Eukarya. Criteria for classification have historically been based on similarity in form. However,
modern technologies, including analysis of the DNA, are allowing biologists to revise and refine
traditional classification schemes, with the ultimate goal that classification should reflect the
evolutionary relationships of organisms. The 3-domain system of classification should therefore
be viewed as a dynamic theory which, like all good scientific hypotheses, may be amended as
new information comes to light.
In the 3-domain system, the domains Archaea and Bacteria consist of prokaryotic cells,
whereas the domain Eukarya consists of eukaryotic cells. Within the domain Eukarya, the
kingdom Protista consists of generally unicellular organisms. The kingdoms Plantae, Fungi,
and Animalia are multicellular. These can be further classified on the basis of their way of
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acquiring nutrients. Members of the kingdom Plantae photosynthesize, that is, they combine
carbon dioxide and water in the presence of light to create the sugar glucose. Members of the
kingdom Fungi secrete enzymes outside their bodies and then absorb the externally digested
nutrients. Members of the kingdom Animalia ingest their food and then digest it.
In today’s lab, you will observe representatives of each of the five kingdoms with the use of a
compound light microscope. Neither as primitive as Robert Hooke’s instrument, nor as
sophisticated as an electron microscope (nor as expensive!), light microscopes remain the
mainstay of modern biological research and education.
The Compound Light Microscope (see figure on next page)
The compound light microscope is a precision instrument, and should be handled with great
care. All of the instructions given in this laboratory are designed to help you get the most from
your use of the microscope and to ensure that it is well maintained for other students. To help
you learn how to use the microscope, your instructor may show you a short video (How to use a
Microscope) before you begin the lab exercises.
Working with a partner, obtain a prepared “letter e” slide. Find the stage on the microscope you
will share. Its purposes are (1) to support the slide, and (2) to allow the slide to be moved
beneath the objective lens so you can examine different parts of the specimen on the slide. Open
the spring-loaded finger of the specimen holder with one hand, and insert the “letter e” slide
into the holder with the other hand. Release the finger gently after the slide is placed inside the
holder. Using the stage control (the vertical dial below and to the right of the stage), observe how
the slide can be moved right & left, forward & backward, so as to position different parts of the
specimen above the hole in the stage.
This hole allows light emitted from the illuminator at the bottom of the scope to pass through
the specimen you are viewing. The light is turned on and off by a switch, and its intensity is
controlled by a rheostat (voltage control dial). For the Olympus CH2 model microscope, the
switch is at the front left corner and the rheostat on the right-hand side; for the Olympus Ch30
model, the switch and rheostat are on the right arm of the scope. Make sure the rheostat dial is
set no higher than “3”, and then turn on the illuminator switch. Turning on the illuminator at
higher intensities quickly burns out the microscope bulb or fuse.
This tool is called a compound microscope because the image is magnified by a set of two
lenses: one in the eyepiece (the ocular lens) and one which is mounted on a revolving nosepiece,
the objective lens. Note that there are three different objective lenses mounted on the revolving
nosepiece. The shortest lens (color-coded red) magnifies the specimen four times (4X), and the
next longest lens (color-coded yellow) magnifies it ten times (10X). These are both considered
low power objectives. The longest lens (color-coded blue) is that of the high power objective,
which magnifies the specimen forty times (40X). You should always begin your observation
of a specimen on a low power objective, 4X or 10X. Make sure now that the 4X objective is in
place and, if it is not, turn the nosepiece until it “clicks” into place.
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Figure 1. A Nikon Compound Microscope.
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Locate the coarse and the fine adjustment knobs on the side of the scope. The coarse
adjustment knob is the larger of the two knobs, and the fine adjustment is the smaller. Now
look through the eyepieces, which contain the ocular lenses. Turn up the rheostat just enough so
that you can comfortably see the image. Use the coarse adjustment knob to bring the specimen
(the letter “e”) into view. This action changes the distance beween the objective lens and the
stage. Now turn the fine adjustment knob to bring the specimen into the sharpest view you can.
When using the fine adjustment, it is best to choose some sharp edge in the specimen to focus on.
The distance between the two oculars of the eyepiece can be adjusted to match the distance
between your eyes. Move the two oculars in and out until you can comfortably see a single
image. Note that there is a numerical scale between the two oculars. Write down the number on
the scale at which you comfortably see a single image. By returning to this inter-ocular distance
after another student has used the microscope, you can customize its setup for yourself. The left
ocular also contains a diopter adjustment ring, to accommodate any difference in acuity
between your right and left eyes. To customize this feature, first bring the specimen into focus
with both eyes open. Next, close your left eye and use the fine focus adjustment to bring the
specimen into best focus for your right eye. Now, open your left eye and close your right eye.
Rotate the diopter ring on the left ocular to bring the specimen into its sharpest focus for your left
eye. Finally, with both eyes open again, you will have the best focus possible for your eyes.
What do you notice about the orientation of the letter “e” when viewed through the microscope?
The magnification of the ocular lenses is 10X. Thus, the ocular lenses make the specimen appear
ten times larger than it actually is. Since both the ocular and objective lenses magnify the image,
the total magnification is computed by multiplying the magnification of the ocular lens (10X)
by the magnification of the objective lens. In this case, with the lowest power objective (4X) in
place, the total magnification is 10X x 4X, or 40X. The letter “e” appears 40 times larger than
when viewed with the unaided eye. (Refer also to the poster “Microscope Magnification” in the
lab; a small copy is included with this laboratory).
What is the total magnification of a specimen when the high power objective (40X) is being
used?
Now, turn the revolving nosepiece to change from the 4X objective to the 10X objective. As long
as the specimen was in good focus at the lower magnification, it should only need minor
adjustment with the fine adjustment knob to bring it into sharp focus at a higher power objective.
You may need to increase the light intensity somewhat at this higher magnification. Again, use a
sharp edge of the specimen when making fine focusing adjustments. As you turn the focal
adjustment knobs, you may reach a stopping point. Do not force the knob beyond this point.
Doing so may strip the threads of the focal adjustment and damage the microscope. Instead,
inform your Instructor of the problem.
Finally, after the specimen is in sharp focus with the 10X objective, switch to the highest power
objective (40X) by rotating the revolving nosepiece until the objective clicks into place. Increase
the light intensity slightly. Notice that the distance between the objective lens and the slide is
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very small at this point. You should never use the coarse adjustment on high power! Even a
small turn of thecoarse adjustment knob may cause the objective lens to crash into the slide,
irrevocably damaging both. Instead, use only the fine adjustment knob to bring the specimen
into sharp focus.
There is one other lens system on the compound microscope of which you should be aware. This
is the condensor lens, which is situated between the illuminator and the stage. As its name
suggests, its function is to “condense”, or concentrate, the light from the illuminator onto the
specimen through the hole in the stage. It does not magnify or otherwise change the apparent size
of the specimen. Notice the condensor height adjustment knob on the left-hand side of the
condensor lens, which moves the condensor lens towards or away from the stage. While looking
through the eyepiece, use the knob to move the condensor lens up and down, and observe how
the light intensity changes. For the purposes of this course, you should keep the condensor lens
as far towards the stage as it will go (i.e., maximum brightness).
You should also know about another way the light intensity can be adjusted. Locate the aperture
iris diaphragm lever, which controls the amount of light coming through the condensor lens.
While looking through the eyepiece, move the lever back and forth and observe how the light
intensity changes. A common problem among beginning students of the microscope is to use far
more light than is necessary to view the specimen. This not only decreases the life of the
illuminating bulb but, more importantly, may give you a nasty headache from eye strain by the
end of the lab session. Look at the number on your rheostat dial. With the 40X objective in place
and the iris diaphragm opened for maximum brightness, if the number is higher than 6 (for the
Ch2 model; 4 for the CH30 model), your illuminator is too bright and you should turn down the
rheostat! In general, you should keep the iris diaphragm all the way open and use only as much
light from the illuminator as necessary to clearly view the specimen.
Return the “letter e” slide to its box when you have completed the above exercises.
Microscopic Measurement
To find the length of something like this piece of paper, you need a ruler marked in specific
units. To measure the size of a cell under the microscope, you also need a unit of measure or
some frame of reference. Most microscopes have “ruler” in one of the oculars of the microscope
(it’s best to shift the one with the ruler to your dominant eye). There are two possible types of
ocular rulers: tick marks ranging from 0 to 10, or tick marks ranging from 0 to 100.
• If your ocular ruler has tick marks ranging from 0 to 10 as in Figure 2A, the results will be
given in centimeters, cm. For example, the object in figure 2A is about 5.8 tick marks in length
under a magnification of 400, so its actual length is 5.8/400 = 0.0145 cm. There are 10
millimeters in 1 cm, so the object is 0.145 mm.
• If the ocular ruler has tick marks ranging from 0 to 100, the results will be given in
millimeters, mm. In Figure 2B the object is approximately 42 tick marks under a magnification
of 400, so its actual length is 42/400 = 0.105 mm.
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To measure the length of an object, place one tip of the object at the zero point on the ocular
ruler using the stage adjustment knob and estimate it’s length in tick-marks. Next, divide the
number of tick marks by the total magnification under which you are view the object.
Before the use of the microscope as a biological tool, scientists had no need of units smaller than
a millimeter. For microscopic measuring, the millimeter itself is divided into 1000 parts. One of
the parts is called a micrometer, µm. A micrometer is one thousandth of a millimeter. How
many micrometers are there in 4 mm? Since there are 1000 µm in 1 mm, there are 4000 µm in 4
mm.
How many µm in 56 mm?
How many µm in 2.5 mm?
You should also be able to change micrometers to millimeters. To do this, you divide the
number of micrometers by 1000. How many millimeters are there in 8000 µm? 8000 µm
divided by 1000 = 8 mm.
How many mm in 1800 µm?
How many mm in 425 µm?
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Comparing Cells from the Three Domains of Life
Work with a partner as you examine the following cell types. Representative specimens
of the 3 domains are presented in an order we believe will best enable you to develop
skill in using the microscope. Make careful drawings and notes. There will be a lab
practical quiz next week on the microscope and cell types.
Domain Eukarya - Kingdom Protista
There may be a poster “Freshwater Protists” in the lab, which shows some of the diversity within
this kingdom. You may also use the index in the back of your textbook to find pictures of these
organisms in your book.
1. Paramecium caudatum
Obtain a prepared slide of Paramecium caudatum. Using the lowest power objective (4X), scan
the slide to find several Paramecium. Bring the cells into focus at 4X with the coarse and fine
adjustment knobs, then switch to the 10X objective and focus with the fine adjustment.
These slipper-shaped protists are normally transparent but have been colored with a stain in the
preparation of the slide to make them more visible. Each cell is surrounded by a plasma
membrane. Within the cell is the pink-stained cytoplasm and the darker pink nucleus.
Now place one cell in the middle of the field of view and switch to the high power (40X)
objective. Using the fine focus adjustment knob only, examine the thin blue “halo”
surrounding the edge of the cell. These are cilia, which the living organism uses for locomotion.
Like thousands of microscopic oars working together, the cilia move the cell through water.
Now focus again on the cytoplasm. You may be able to see some lighter-stained spheres within
the cytoplasm. These organelles (membrane-bound “little organs”) are vacuoles which process
food and water. Depending on the metabolic activity of the cell when it was prepared for the
slide, you may see many or no vacuoles. If you cannot see any vacuoles in the cell you are
examining, switch back to the 10X objective, select a different Paramecium cell, return to 40X,
and look again.
What is the size of a Paramecium cell in your slide? Show your work. Be sure to express your
answer in µm.
Using the 40X objective, draw what you see. Label the plasma membrane, cytoplasm, nucleus,
cilia, and vacuoles. Provide a brief title for your drawing so you and your Instructor know what
you were looking at. Create a scale bar for your sketch by drawing a line along the length of the
cell and indicating the cell’s size (in µm).
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Return the prepared slide to its box when you have finished your observations.
2. Euglena spp.
Obtain a prepared slide of Euglena. Locate and focus on a number of cells with either the 4X or
10X objective. You will probably notice that, even with the 10X objective, you cannot see much
detail, so you will want to increase the objective lens magnification to 40X. As with
Paramecium, these cells have been stained in preparing the slide, and you should be able to
identify the plasma membrane, cytoplasm, and nucleus.
Like Paramecium, Euglena are members of the kingdom Protista because they are single-celled
eukaryotes. Unlike Paramecium, however, Euglena do not propel themselves with the use of
cilia. Instead, they have a single flagellum, a thin, tail-like structure which moves the living cell
by means of quick undulations. Using the 40X objective, select an individual cell and, using the
fine focus knob, examine the tapered ends of the cell to find a flagellum. Some of the cells may
have lost their flagellum in the preparation of the slide, so examine several cells if necessary
until you find a flagellum.
Using the 40X objective, draw what you see. Label the plasma membrane, cytoplasm, nucleus,
and flagellum. Provide a brief title for your drawing. Estimate the size of the cell (in µm), and
include a scale bar for your drawing.
Return the prepared slide to its box when you have finished your observations.
Kingdom Plantae - Elodea leaf
Pinch off a leaf of live Elodea (a common freshwater aquarium plant) and place it on a clean
glass slide. Try to get a leaf from the growing tip of the plant. Handle the slide by its edges to
avoid fingerprints. Add ONE DROP of water to the slide, placing it directly over the leaf and
making sure not to flood the slide with too much water.
A cover slip is a thin piece of glass or plastic which is placed over the specimen. Hold the cover
slip in position at one edge of the water drop, and gently lower it. If you just plop the cover slip
on the specimen, you will trap air bubbles which will interfere with your view of the specimen. If
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you have too much water on the slide, you will find that it runs over the top of the cover slip.
Remove excess water with the edge of a Kimwipe before viewing the slide. The preparation you
have just made is called a wet mount.
Place the wet mount under low power (10X) and examine the leaf. Notice that there are several
layers of cells in the leaf. Carefully focus up and down, noting that the cells have depth to them.
How many layers of cells are present in your leaf?
What is the size of an Elodea cell in your slide? Show your work. Be sure to express your answer
in µm.
Under high power (40X) examine a single cell and carefully study its structure in detail. You will
note that each cell is surrounded by a rigid cell wall composed of cellulose. The cell wall is
characteristic of plant cells. The cell membrane is pressed up against the inner side of the cell
wall and is too thin to be visible under a compound light microscope. The cytoplasm consists of
all the living material inside the plasma membrane, except for the nucleus. Within the cytoplasm
are many circular green organelles, the chloroplasts. The green color is due to chlorophyll, the
green pigment important to photosynthesis, which is the process by which plants use the sun’s
energy to make their own food (sugars). The chloroplasts may be seen moving around inside the
cell as they are pushed along by the streaming of the cytoplasm, a process known as cyclosis.
Look at cells near the midvein of the Elodea leaf to see if the chloroplasts are moving.
How might cyclosis aid the cell?
The inner portion of the cell consists of a large central vacuole, a membrane-bound sac filled
with fluids or solid matter. It may assume different shapes, sizes, and functions in various cells.
Make a large, clear drawing of one Elodea cell. Label the cell wall, cytoplasm, chloroplasts,
and nucleus. (The nucleus is usually pressed against the plamsa membrane and cell wall and
may be hard to see.) Make a title for your drawing, and provide a scale bar for size. You should
also write down the total magnification that you were using during your observations. Remember
that the total magnification is the ocular power multiplied by the objective power.
When you have finished your observations, discard the leaf in the trash, and discard the cover
slip in the special glass-only box. Rinse the glass slide with water at the sink, dry with a
Kimwipe, and return the clean, dry slide to the glass slide box for use by another student.
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Kingdom Fungi
Fungi are a group of organisms that secrete enzymes to digest their food outside the cell and then
absorb the nutrients across the cell membrane. Like plants, fungi have cell walls, but they are
made of a substance called chitin, rather than the cellulose found in plant cell walls. You are
familiar with some fungi, such as mushrooms. In these, the part we eat is the reproductive
structure.
Mold is another type of fungus. You may have seen bread mold, for example, if you left some
bread in your refrigerator too long. Look through the oculars of the dissecting microscope to
observe the culture of bread mold (Rhizopus sp.) on display. The fibers are the body of the
fungus and are called the hyphae; the interconnected mesh they form is called a mycelium.
Fungi are not made up of individual cells like most other kinds of organisms; instead, the cell
walls are not complete and there may be many nuclei found inside each compartment.
You may see some dark, globular sporangia. These are reproductive structures in which spores
are formed. When mature, the sporangia will burst, releasing spores which are dispersed to
another area suitable for continued growth of the mold.
Draw and label what you see. Provide a brief title, and note from the dial on the top of the
dissecting microscope how many times the specimen is magnified. Because we have not
provided you with the diameter of the field of view at different magnifications for this
microscope, however, do not worry about providing a scale bar for your drawing.
Are any chloroplasts present? Why or why not?
Kingdom Animalia - Homo sapiens Cheek Epithelial Cells
A typical tissue which covers the external surface of the human body is the epithelium. To
observe some of the cells which make up this tissue, your instructor will make slides for you to
observe on the video microscope. These slides were made with the following procedure. First
one drop of water was placed on a clean slide. Next, the inside of the cheek was gently scraped
with a clean toothpick. The scrapings were stirred into the drop of water on the slide. Next, one
drop of toluidine blue or methylene blue stain was added, and then covered with a cover slip.
Observe the cells with the microscope and locate some that are spread out (not bunched up).
Reducing the light by closing down the iris diaphragm may help visibility. The cells should be
pale blue with a darker blue spot inside. They are so thin that some may be folded over. Identify
the plasma membrane, cytoplasm and nucleus. Draw a few cells and label the visible parts.
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With a scale bar, indicate the cell's size on your drawing. Be sure to also provide a brief title and
to include the total magnification.
Do these cells have a cell wall? Why or why not?
Do these cells have chloroplasts? Why or why not?
When the class has finished their observations, the entire wet mount should be discarded
(glass slide, cells, and cover slip) in the special glass-only box.
Domain Bacteria
All prokaryotic cells belong to the domain Bacteria and Archaea. Although these are the most
primitive of the cell types (that is, they evolved before eukaryotes), we have kept them until last
because their tiny size makes them difficult for beginning students to focus on. Most prokaryotes
are less than 5 µm long; compare this to the cells you have already measured to appreciate their
diminutive size. Look at the poster “Bacteria” in the lab.
Obtain a prepared slide of bacteria. There are 3 different kinds of bacteria on this slide; each is
separately prepared as a “smear”. Locate one of these smears under lowest power (4X) and
focus; increase the objective magnification to 10X and then to 40X.
Use the micrometer to estimate the size of one bacteria cell.
Can you see any structural details inside the individual cells?
Because of their small size, even at the highest magnification of the best compound light
microscopes, very little can be seen of the cellular details of prokaryotes. Instead, our
knowledge of the fine structure of prokaryotes comes from high-powered electron microscopes.
From these microscopes we know that prokaryotes do not have discrete organelles (e.g., nucleus,
chloroplasts, vacuoles) such as you saw in the other cells you examined today. Biologists have
traditionally used other properties of bacteria, such as their shape, the stains they absorb, and the
media on which they will grow, to distinguish among different species. The bacteria on this slide
are stained by a method called the Gram stain, which renders the species either purple or pink.
Depending on which of the smears you are looking at, the shape of the bacteria may either be
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round, rod-shaped, or spiral.
Indicate the color (pink or purple) and shape (round, rod, or spiral) of the bacteria you are
looking at.
Look at the other smears on the slide. What color and shape are they?
Return the prepared slide to its box when you have finished your observations.
Putting Away the Microscope
When you are finished using the microscope, you should always:
1. Remove the slide you have been examining and return it to its proper place.
2. Turn down the rheostat to “3” or lower.
3. Turn off the illuminator switch.
4. Revolve the nosepiece so the 4X objective is in place.
5. Wrap the cord properly around the microscope.
Conclusions
Review your observations of the variety of cells that you have examined. Be prepared for a lab
practical quiz next week.
1. What are two differences between eukaryote cells and prokaryote cells that you can observe
with a compound light microscope?
2. What are two differences between plant and animal cells?
3. Be prepared for a quiz next week!
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Lab 4: Cellular Transport: Brownian Motion,
Diffusion, and Osmosis.
Introduction
In order for a living cell to function, nutrients, water, and oxygen must enter the cell while waste
products must leave. The avenue for substances entering the cell is the plasma membrane.
Many of the physical phenomena that occur in living systems, such as diffusion, osmosis, and
Brownian motion, occur because molecule are in constant vibratory or oscillatory movement in
cytoplasm (also called protoplasm). In the following exercises, you will be concerned with some
of the more important chemical and physical phenomena that affect the function of living cells.
The cell, usually a microscopic entity, is a physiochemical system the activities of which are
based on certain physical and chemical phenomena. A fundamental requirement for the proper
function of cells is that molecules and atoms involved in cellular processes move quickly from
one place to another, e. g., either between extra- and intracellular spaces or from one intracellular
location to another. One chemical process may require a constant source of raw material which
it itself the product of an intracellular reaction occurring at some distance away. The cell is
microscopic to us and therefore seems extremely small. But it is truly a molecular macrocosm in
which molecules move long distances (up to 100,000 diameters) within a moment of time. This
movement is the result of random molecular motion, which is the basis for molecular processes
to be examined in this lab.
The concept of random molecular motion is a fundamental theory of biological and physical
sciences referred to as the kinetic molecular theory of matter. This theory decrees that all
atoms and molecules are constantly in a state of motion, whether they be constituents of gas, in
which particles are relatively free to move, a liquid, where freedom of movement is somewhat
more restricted due to the abundance and proximity of adjacent particles, or a crystalline solid,
where movement is quite restricted do the ordered state of surrounding particles.
As these particles race about, they constantly collide with, reflect, repel, and glance off one
another; each particle may collide with tens of thousands of other particles in the time span of a
single second; and will change directions as many times. We consider the vast number of
particle contained in any macroscopic bit of matter (6.02 x 1023 molecules of water in ½ ounce
of water) described above, a picture mass chaos emerges.
Although we are unaware of the chaotic state of matter around or within us, each of us invokes
the principle of random motion when we use the terms heat and temperature. Consider the ½
ounce of water mentioned previously. The speed of each water molecule (as well as its size)
determines its energy of motion, or its kinetic energy. However, not all particles in our sample
are moving at the same speed and thus do not have the same kinetic energy. If we sum the
individual kinetic energies so we know the total kinetic energy of our sample, the resultant
quantity is its heat content. Heat is defined as the total kinetic energy of a system, in this case
our water sample. Thus, when we speak of heating water for coffee we are actually alluding to
an increase in chaotic motion within the water. If we divide the total heat content by the number
of particles in the sample, the resultant quantity is the average kinetic energy per particle. We
are measuring this average kinetic energy when we determine the sample’s temperature. An
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increase in temperature would indicate an increase in the average kinetic energy of particles in
the sample; a decrease would reflect a lower average kinetic energy. It easily follows that a
change in heat content will necessarily result in a change in temperature.
NOTE: Set up Part III of this lab first!!
I. Brownian Motion
Under high magnification, small organisms such as bacteria, or other small particles appear to
jiggle in an random, ceaseless manner. This motion, first observed by the English botanist,
Robert Brown, is due to the bombardment of these tiny organisms or particles by even smaller
particles (molecules). This so-called Brownian motion illustrates the kinetic nature of matter,
which is the basis for such physical phenomena as diffusion.
In this exercise, you will be observing molecules of india Ink, which are dark, colored and large.
Place a drop of water in the center of a slide. Then lightly touch with the tip of India Ink stopper.
Put a cover slip over the drop and observe. Focus carefully on the very tiny drops of ink, and
observe their random jiggling motion.
Write a brief explanation (not just a description) of your observation, relating it to the kinetic
molecular theory of matter.
II. Diffusion
Diffusion can be defined as the movement of matter from an area of high concentration to an
area of low concentration. This process of diffusion is critical to the proper functioning of living
systems. A firm grasp of this phenomenon is essential to your understanding of physiology.
This process is highly predictable in the macroscopic and microscopic realms and yet is the
result of the unpredictable random movement of individual particles. For instance, if we open a
bottle of ammonia on one side of a room we will eventually be able to detect ammonia in the air
on the other side of the room. The ammonia has moved from an area of high concentration to an
area of low concentration, a process we now recognize as diffusion. Can you explain the process
of diffusion by invoking the theory of random molecular motion?
Consider the state of room air before you open the ammonia bottle. All molecules are moving
about in random chaotic fashion; the movement of individual particles is not predictable. We
can, however, predict that the total number of particles moving in a particular direction, say up,
is exactly balanced by the total number of particles moving in the opposite direction, down in
this case. If this were not so, all the molecules at the top of the room would eventually end up at
the bottom of the room (or visa versa); and the op would be devoid of air. We can now relate a
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random phenomenon to predictable observation: although the behavior of individual particles is
not predictable, we can predict that there will be no net movement in any direction. The same
conditions exist in the ammonia bottle. However, when the ammonia bottle is opened, molecules
which were rebounding off the lid will continue to move up and out of the bottle but these must
be replaced because there can be no net movement of matter. Since there are no ammonia
molecules outside the bottle, air molecules must move into the bottle to replace those ammonia
molecules which leave. No net movement of matter has occurred but there has certainly been a
net movement of ammonia out of the bottle and a net movement of air into the bottle. Thus we
have diffusion of both ammonia and air.
Procedure:
Students should work in groups of 4.
For this exercise you will need a Petri dish, thin ruler, cold food coloring, and cold distilled
water.
1. Center a thin ruler (paper rulers will be provided) under a large clear Petri dish.
2. Pour 50 ml of cold distilled water into the dish and allow it to stand for a few minutes.
3. Into the center of the dish, carefully add one drop of cold food coloring – trying not to disturb
the water.
4. Measure the diameter in millimeters of the darkest colored spot at 30-second intervals for 15
minutes. Record data in the worksheet below and graph the results.
5. Does the net movement of molecules slow down as equilibrium is reached? Explain.
6. Does the diffusion eventually come to an end? Why?
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Graph the results below with the X-axis = time
and Y-axis = diffusion in mm.
Time
Diameter
(mm)
0
.30
1.00
1.30
2.00
2.30
3.00
3.30
4.00
4.30
5.00
5.30
6.00
6.30
7.00
7.30
8.00
8.30
9.00
9.30
10.00
10.30
11.00
11.30
12.00
12.30
13.00
13.30
14.00
14.30
15.00
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1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
TIME /min
34
III. Osmosis: Diffusion of water across a semi-permeable membrane
The bodies of organisms contain a great deal of water within which is dissolved atoms, ions, and
molecules important to the growth of the organism. These mixtures of water and particles are
termed solutions wherein water is the solvent and the dissolved particles are the solute.
Remember that you are composed of 75 trillion cells, each of which carries on all function of
life. Inside each cell is a water solution called intracellular fluid in which the cell’s chemical
reaction occurs. All your cells are bathed in a watery solution (extracellular fluid) from which
they get all the chemicals necessary for their operations.
When an animal cell is bathed in the watery fluids of the body (as are all living cells), the
contents of the cell are separated from these fluids by the cell membrane (plasma membrane).
The cell membrane permits the water molecules to pass freely through in both directions, but
prohibits larger particles of particular sizes, geometric, and charge distributions from either
entering or leaving. Such a membrane, which permits some objects to pass through but not
others, is said to be semi-permeable or selectively permeable.
Intracellular fluids and the extracellular fluids contain more than just pure water. They are both
solutions. When there are many solute particles relative to the number of water molecules, the
solution is said to be concentrated. When there are few solute particles and many water
molecules, the solution is said to be dilute.
The term tonicity is used to refer to the relative number of particle (solute) dissolved in water
(solvent). If the solution inside a cell (intracellular fluid) and the same relative number of particle
as the solution (extracellular fluid) surrounding the cell, the two solutions are compared using the
term isotonic; iso-meaning the same and tonic referring to relative solute concentration. Note
that when two solutions have the same relative concentrations of particles (isotonic), they also
have the same relative concentrations of water. Hence as water moves freely across a cell’s
membrane, there will be no net movement of water, as there is no concentration gradient for the
molecule.
A solution having the same ratio of water molecules to particle as the solution inside the cell is
said to be isotonic to the cell. If the concentration of particles outside the cell exceeds the
concentration of particle within the cell, then the cell exist within a hypertonic (hyper = high)
environment. It could also be said that the cell’s content are hypotonic (hypo = low) to the cell’s
external environment. In such a case, there will be fewer water molecules outside the cell than
within the cell, and water will leave the cell by diffusion because of the gradient. In the opposite
case, where there is a greater concentration of particle within the cell than in the cell’s extern
environment, the cell is said to exist in a hypotonic environment. Alternatively, it can be said
that the cell’s contents are hypertonic to the cell’s external environment. In this case, water will
enter the cell by diffusion. The process by which water molecules diffuse through a semipermeable membrane from an area of higher water concentration to an area of lower water
concentration until equilibrium is achieved is known as osmosis.
In this exercise you will be placing cells of a potato (which have semi-permeable membranes)
into different concentrations of sugar water.
Procedure:
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Students should work in groups of 4. Each group should turn in one copy of pages 36-38.
1. Get 4 beakers (or cups) and pour 300 ml of solution into each beaker – one sucrose solution
concentration into each beaker:
1.
2.
3.
4.
0 mg/ml
5 mg/ml
20 mg/ml
40 mg/ml
Note: The concentrations were calculated using the following formula:
Concentration = mg of sucrose/ mg of sucrose + ml of water
2. With a cork borer (or knife), cut four pieces of potato about the same size. Measure the
weight of each piece. Keep track of the weight of each piece.
3. Place one potato piece in each solution. Make sure to keep track of which piece is in which
solution!! Label your beakers with a wax pencil or place a piece of paper in front of each beaker
labeling the sugar concentration and the weight of the potato piece in that beaker.
4. After one hour, remove the potato piece, blot it with a paper towel, and weigh it. In the table
on the following page, record the percent change in weight. Label your table appropriately.
Percent change = (Post experiment weight – Pre experiment weight) x 100
Pre experiment weight
For example: if your potato piece weighed 25 grams before and 35 grams after.
Percent change = (35 – 25) x 100 = 40% change
25
if your potato piece weighed 40 grams before and 32 grams after
Percent change = (32 – 40) x 100 = -25% (negative because it lost weight).
40
5. Be sure to clean your equipment and your desks. The solutions can be poured down the sink.
The potato pieces should be thrown in the trash.
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Pre-weight
Post-weight
% change
0 mg/ml sucrose
5 mg/ml sucrose
20 mg/ml sucrose
40 mg/ml sucrose
Make a line graph of your results with concentration on the X-axis the % change in weight on the
Y-axis (your Y-axis will probably go into negative numbers). Label your graph appropriately.
1. Which piece(s) of potato gained weight? Why?
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2. Which piece(s) of potato lost weight? Why?
3. From your graph, estimate the concentration of solution inside the cells of the potato. That is,
what concentration of sucrose solution (extracellular fluid) would be isotonic with the
intracellular fluid of the potato?
IV. Plasmolysis of Elodea
Obtain two slides. Place a drop of water on one slide and a drop of salt solution on the other
slide. Place a leaf from an Elodea plant on each slide. Wait about 5 minutes. Place a cover slip
on the slides and observe them under a microscope. What has happened to the leaf in the salt
solution?
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Lab 5: Cellular Respiration - Alcoholic Fermentation
Introduction
Alcoholic fermentation is a metabolic pathway used primarily by yeasts and some bacteria when
oxygen is not present. In fermentation, glucose is broken down into ethyl alcohol (ethanol) and
carbon dioxide (glucose Æ alcohol + CO2 + ATP). In the process, some of the energy that had
been stored in the glucose bonds is used to form high energy bonds in ATP. A series of enzymecatalyzed reactions is needed to complete the conversion of glucose into alcohol, carbon dioxide,
and ATP. Therefore, any of the factors that affect enzyme activity can affect the rate at which
fermentation occurs.
Name some factors that affect enzyme activity.
Although glucose is the substrate at the beginning of the pathway, keep in mind that other
molecules can be changed into glucose and used in cellular respiration. For example, starch or
glycogen can be broken down into their many component glucose molecules. Sucrose (table
sugar) can be broken down into its two component sugars, glucose and fructose. The fructose
can then be converted to glucose by another enzymatic process.
In the procedure you will use, fermentation is performed by yeasts, single-celled fungi. That is,
yeasts contain the cellular machinery, including the enzymes, which is capable of breaking down
glucose by alcoholic fermentation. Corn syrup, which contains sucrose and fructose, will be
used as the substrate. You will measure the rate of alcoholic fermentation by collecting carbon
dioxide (C02), which is one of the products, at intervals after fermentation has begun.
Figure 2 shows the set-up you will use to collect the CO2. Fermentation will take place in the
test tube on the right, which contains the yeast and corn syrup, the fermentation solution. The
test tube is capped with a rubber stopper to prevent CO2 from escaping. Plastic tubing leads from
the fermentation tube to the CO2 collection tube, which is upside down and contains water. As
CO2 is produced by fermentation, it goes through the tubing into the collection test tube, where it
displaces the water. The displacement (in mm) is recorded as a measure of the amount of CO2
produced.
Procedure:
Students should work in groups of 4. Each group should turn in pages 42-43.
1.
You will need to have three fermentation set-ups, so you should have six large test tubes,
three pieces of plastic tubing that have been inserted into rubber stoppers, and three beakers
(400- or 600-m L). Using a wax pencil, label three of the test tubes 1, 2, and 3 and set them
aside. Assemble the set-ups one at a time following steps 2-7 (see Figure 2).
2.
Fill a tub or sink with hot water (50o - 60o C).
3.
Insert the end of the plastic tubing into one of the test tubes. This tube will be the CO2
collection tube. Submerge the collection tube and plastic tubing in the tub of hot water.
4.
Submerge the beaker. Place the collection tube in the beaker in an inverted position
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Figure 1. Apparatus for measuring CO2 production in alcoholic fermentation.
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5.
Bring the beaker out of the water. One end of the plastic tubing should still be inserted in
the collection tube. Hold up the other end of the tubing (the one with the rubber stopper on
it) so that the water won’t be siphoned out. It is okay if there is still a little air in the
collection tube.
6.
Pour some water out of the beaker so that the water level is at least 3-4 cm from the top of
the beaker.
7.
Check the tubing for kinks. If the CO2 can’t get through the tubing, you’ll have to start
over.
* Assemble all three set-ups before proceeding to mix the fermentation solutions.
8.
Mix the fermentation solutions for Tubes 1, 2, and 3 according to Table 1. Put the yeast in
the tubes last.
Table 1. Contents of fermentation tubes.
Tube 1
Water
4 ml
Tube 2
3 ml
Tube 3
1 ml
Corn syrup
3 ml
3 ml
3 ml
Yeast suspension*
0 ml
1 ml
3 ml
*Yeast suspension is 1 packet of yeast mixed with 50ml of warm water.
9.
Swirl each test tube gently to mix the reactants. Place one test tube in each beaker.
10. Put the rubber stoppers in the fermentation tubes. This will force most of the water out of
the tubing.
11. After the air bubbles from inserting the stopper have cleared the tubing (half a minute to a
minute), mark the water level on each collection tube with a wax pencil. This marks the
baseline for your experiment.
*If the water level is all the way to the top of the collection tube, where the tube is
curved, you should wait until it has descended to the part of the tube where the sides are
straight before you mark the level.
12. For the first 10 minutes, measure (in mm) the distance from the baseline mark to the water
level in the tube. Then, for 20 more minutes, measure at 5-minute intervals. Record your
data in Table 2.
13. When you are finished, make sure you clean your equipment and desks. The solutions can be
poured down the sink.
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Table 2. Results of fermentation experiment.
Minutes
2
4
6
8
10
15
20
25
30
Tube
1 (no yeast)
2 (1 ml yeast suspension)
3 (3 ml yeast suspension)
While you are waiting to collect data, look again at Table 1 to see how the experiment was
designed. Answer the following questions.
1. What is your hypothesis for this experiment?
2. Which fermentation tube was the control?
3. Why were different amounts of water added to each fermentation solution?
4. What are some other factors that could affect alcoholic fermentation?
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5. Was your hypothesis supported or proven false by the results? Use data to support your
answer.
6. Using the class data, average all of the groups’ results for each tube and plot the average
water displacement for each time period. Plot the averages for each time period for all three
tubes on one graph. This shows the reaction rate (CO2 produced/time). The steeper the slope of
the line, the faster the reaction rate. Be sure to label the graph completely.
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Lab 6: Photosynthesis in Coleus Leaves
Introduction
In photosynthesis, plants use energy from the sun to convert CO2 into sugars. The molecule that
harvests the sun’s energy is the green pigment chlorophyll which is found in the chloroplasts of
the plant cells. The sugars that are made by the chloroplast are then used by the plant in cellular
respiration, or are stored as starch for later use. Plants also have pigments of other colors that
may also be involved in photosynthesis.
In this lab, you will determine the relative amounts of starch in the leaves of coleus plants
(Coleus bicolor) that have been exposed to different environmental conditions and the impact of
chlorophyll and plant pigments on the starch storage. Iodine turns a dark blue-black color in the
presence of starches. Be careful, as iodine will also stain your clothes and your skin.
Initially, both plants were grown in bright, sunny conditions. One week prior to this lab, one set
of plants was placed in a very dark space and received little light. These plants are labeled
DARK. The other set of plants remained in bright sunny conditions. These plants are labeled
LIGHT.
Procedure:
Students should work in groups of 4. Each group should turn in pages 45-47.
1. Write your hypothesis for this experiment on the next page.
2. CAUTION: You will be boiling various liquids in beakers. Do not handle the hot beakers
without protective mitts.
3. Remove one leaf each from a DARK plant and a LIGHT plant. Be sure to keep track of
which leaf is which by choosing different sized leaves or cutting the petiole (stalk) off of one,
and writing down which is which.
4. Sketch each leaf on the next page, showing where the green, white, pink, and purple (which is
made by both green and pink) are found.
5. Boil both leaves in one beaker of water on a hot plate to remove the water-soluble pigments,
which are pink to purple. Use just enough water to cover the leaves.
6. Remove leaves gently from the beaker of water and place them on paper towels, or float them
in a shallow dish of water. Sketch the leaves again to show the new color pattern.
7. Blot off excess water before the next step (otherwise the second extraction will be poorer).
Place blotted leaves in a small beaker with just enough alcohol to cover the leaves. Place the
small beaker inside a larger beaker with about 2 inches of water in it and let the small beaker
float. Place on hot plate and heat. DO NOT allow alcohol to boil vigorously!! Boil leaves until
they turn almost white and most of the green chlorophyll is extracted.
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8. Put leaves in shallow dishes and flatten them out. Add plenty of iodine solution to cover the
surface of the leaves. Tap all over the surface of the leaves using the tip of the dropper, to get
the iodine solution into the leaf tissue. Note any color changes.
9. Sketch the leaves a third time, indicating the locations where starch is present.
10. Compare your leaves with other groups.
11. Be sure to clean your equipment and desks. Put used alcohol in the marked waste container.
Water can go down the drain. Leaves should be thrown in the trash.
Sketches:
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Sketches:
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Answer the following questions:
1. What is your hypothesis for this experiment?
2. Did the results support your hypothesis or not?
3. Is chlorophyll soluble in water?
4. Describe the pattern of starch presence in the different colors of the DARK and LIGHT
leaves. Were they the same or different? Why?
5. What pattern of starch presence likely existed in the DARK leaf before it was placed in the
dark? Why is it different now?
6. What relationship is there between starch and chlorophyll in the leaves?
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Lab 7: Nuclear Division: Mitosis and Meiosis
Introduction
Genetics is the branch of science that studies the nature of inheritance. Just as life on Earth is
organized and can be studied on a hierarchy of levels, so too, can genetics be studied on a
number of levels. As you study genetics, try to ask yourself what level of organization is being
examined: molecular, cellular, species, or population? In today’s laboratory you will first
examine genetics at the cellular level; you will specifically study the movement of
chromosomes during nuclear and cell division. You may also see a video which examines some
of the problems that arise in humans when there are mistakes in the proper movement of
chromosomes during nuclear and cell division. Later, at the species level of organization, you
will explore some of the human traits which are determined by specific areas of DNA (referred
to as “alleles”) on the chromosomes. DNA, the molecular level of genetic material, will be
discussed in lecture. Genetics at the level of the population is the foundation of evolution,
which you will study in a later laboratory.
The purpose of the first part of this lab is to become familiar with the two processes of nuclear
division, mitosis and meiosis, and to understand how genetic information is passed from cell-tocell and from generation-to-generation. The second part of this lab is to become familiar with
different types animal cells and tissues. Mitosis and meiosis are types of nuclear division.
Mitosis is the process of nuclear division that carries the genetic information contained in strands
of DNA to new cells during an organism s growth or during asexual reproduction. Cancer, a
prevalent disease in our society, is the result of uncontrolled mitosis. It’s important for you to
study the process of mitosis so that you can understand the attempts of scientists to cure cancer.
Meiosis is the process of nuclear division that carries the genetic information to sex cells or
gametes for the purpose of sexual reproduction. An important result of meiosis is genetic
diversity, which is fundamental to the survival of species and to evolution. Cytokinesis
describes the division of the cytoplasm that usually accompanies nuclear division. Thus, the
division of the cell is actually two events: either mitosis or meiosis, and cytokinesis.
Make careful drawings and notes during this lab. There will be a lab practical quiz next week!
Mitosis:
The Basis of Growth & Asexual Reproduction
All organisms produce new cells by cell division. When a cell divides, the information contained
in the genetic material (the DNA) must be duplicated and distributed equally to the two resulting
daughter cells. In eukaryotes (cells that have a nucleus), this process of nuclear division is
called mitosis. In unicellular organisms, mitotic cell division is a means of asexual
reproduction. The result of asexual reproduction is a clone of the parent cell since the genetic
information contained in the daughter cells is exactly the same as that contained in the parent
cell. For multicellular organisms, which all begin life as a single cell, mitotic cell division is
involved in growth and repair. Since the strands of DNA are replicated prior to each mitotic
division, each new cell produced contains the same genetic information as the initial cell that
began the organism’s life. Think about this for your own body!
Would you expect that the genetic information in your toes is any different from the
DNA in your heart or your brain? Explain your answer.
In eukaryotic cells the DNA is carried on several nuclear structures called chromosomes. Every
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organism has a chromosome number characteristic of its species. For example, mosquitoes have
6 chromosomes, corn has 20, cats have 38, humans have 46, and dogs have 78. In most animals
and flowering plants, chromosomes can be matched up in pairs. For example, since humans
have 46 chromosomes, they have 23 chromosome pairs. Mosquitoes have 3 chromosome pairs.
The pairs of chromosomes are called homologous chromosomes. A cell that contains pairs of
homologous chromosomes is described as diploid or 2n (for humans 2n = 46). Cells that contain
unpaired chromosomes are called haploid or 1n. Many algae, fungi, mosses, and some social
insects such as male honeybees are haploid.
Chromosomes are quite small and usually appear as a diffuse mass, called chromatin, in the
nucleus. Individual chromosomes can be observed under the light microscope only right before
and during cell division when they condense or coil up into tight, short threads. Before this
condensing, each chromosome has duplicated itself, so that just before nuclear and cell division,
there are 2 identical copies of the original chromosome. These duplicate chromosomes are called
sister chromatids and they are attached to each other at a region called the centromere.
Scientists have divided the process of mitosis into 4 phases for ease of study and
communication. These phases are: prophase, metaphase, anaphase, and telophase. The phase
in between the mitotic stages of cell division is called interphase. It is during interphase that
DNA is duplicated. It is important to keep in mind, however, that there are no pauses between
designated phases and that the life of a cell is always dynamic, never static!
1. Interphase: 1) no nuclear or cell division, 2) cell growth and duplication of genetic material is
occurring, 3) chromosomes are not visible but the cell nucleus and nucleolus are
2. Prophase: 1) duplicated chromosomes condense and become visible as sister chromatids
joined at the centromere, 2) nuclear membrane disintegrates; neither the nucleus nor the
nucleolus is distinct, 3) spindle apparatus of the cell is formed.
3. Metaphase: 1) chromosomes are aligned along the cell’s equator at their centromeres, 2)
spindle fibers are visible
4. Anaphase: migration of the chromosomes: centromeres split and move along the spindle
fibers towards opposite poles, pulling the sister chromatid
5. Telophase 1) chromosomes are aggregated at the poles and begin to thin out and
extend in length, 2) new nuclear membrane forms; nucleolus and nucleus begin to
reappear, 3) spindle disintegrates, 4) cytoplasm divides (cytokinesis occurs); daughter
cells begin to form
Mechanics of Mitosis
Use the various instructiona1 materials available to you in the lab to answer the following
questions:
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How many daughter cells are produced from one parent cell that undergoes mitosis?
If the parent cell contains 4 chromosomes, how many chromosomes will be in each daughter cell
after mitosis is complete? Are the daughter cells haploid (ln) or diploid (2n)?
What are two functions of mitosis for an organism?
Growth and Mitosis in Onion Root Tips
Plant root tips are areas of active growth, and thus, mitosis.
Select a prepared slide of an onion (Allium) root tip to find cells in all phases of mitosis.
Examine the slide first under a low power objective (l0X) of the microscope.
Cells undergoing active growth occur at the tip of the root in the layers beneath the epidermis
(the root’s “skin”). Why is it advantageous for the plant to have the epidermis cover the area of
mitotic division?
Where on your body would you expect mitosis to be frequently occurring? Why?
Now examine the slide with the high power objective (40X) to observe the details of each phase
of mitosis. Find interphase and all four phases of mitosis. Make drawings of each phase and label
all the terms that are In bold type below. Make sure that you label each phase and write down the
total magnification at which you are making your observations.
1) Interphase: Search for a cell in which the nucleus and nucleolus are visible but in which the
chromosomes are not distinct. Draw a cell in interphase.
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During interphase, what is happening to the DNA?
2) Prophase: Search for a cell in which the chromosomes are visible as distinct strands in the
nucleus. Each chromosome is actually composed of a pair of sister chromatids, although you will
probably not be able to see them with the 40X objective. Draw a cell in prophase.
What is the name of the region where the pair of sister chromatids are joined?
Is the DNA in one of the sister chromatids identical to the DNA in its sister, or is it different?
Explain your answer.
3) Metaphase: Find cells in which the chromosomes have lined up across the equator, at the
center of the cell. The chromosomes are attached by their centromeres to the spindle fibers which
extend to the poles of the cell. The centromeres may not be visible in your prepared slide. Draw a
cell in metaphase.
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What specific part of the chromosome is aligned along the equatorial plate.
4) Anaphase: Find cells in which the two chromatids from each chromosome are being pulled
apart at the centromeres. The centromere of each chromosome splits lengthwise, and is pulled
apart by the spindle fiber from the equator to the opposite poles of the cell. Draw a cell in
anaphase.
5) Telophase: Locate cells which show completely separated chromosome groups. Some will
show the nuclear membrane reforming. At this phase, the beginning of cytokinesis can be
observed. Label the daughter cells. Draw a cell in telophase.
How many daughter cells are produced from each parent cell that undergoes mitosis?
Relative to the original parent cell, how many chromosomes are in each of the new cells?
Are the daughter cells haploid (ln) or diploid (2n)?
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Observe the slides of mitosis in whitefish. How is animal mitosis different from plant mitosis?
Meiosis: The Basis of Genetic Inheritance and Sexual Reproduction
In diploid organisms which reproduce sexually, cells in the sexual organs undergo meiosis to
form sex cells (gametes) which have only half the number of chromosomes of body (somatic)
cells. That is, gametes have only one chromosome from each homologous pair and are haploid,
or 1n. Meiosis is the cell division process in which the number of chromosomes is halved as
homologues are separated, and gametes axe formed. Fusion of gametes (fertilization) produces a
new cell called a zygote with the total number (2n) of chromosomes characteristic of that
species. The zygote grows into the embryo and a new organism. Meiosis and fertilization are
the basis of genetic inheritance and sexual reproduction.
The process of meiosis and sex cell maturation in males is called spermatogenesis (“creation of
sperm”); in females it is called oogenesis (“creation of eggs”). Meiosis is a somewhat more
complicated process than mitosis, and includes two rounds of chromosome separation and cell
division. We will not overwhelm you with the details of the process. Instead, look at the drawing
of Animal Meiosis. Note that the first meiotic division results in the separation of the members
of a homologous pair. (Homologous pairs do NOT separate from each other in mitosis.) The
second meiotic division results in sister chromatids separating from each other. The net result of
both meiotic divisions is four cells, each of which has half as many chromosomes as the original
parent cell. Moreover, because the homologous pairs in the first division, and the sister
cbromatids in the second division, separate independently of each other, the resulting 4 cells are
NOT identical to each other. This genetic variability of gametes helps ensure the creation of a
unique new individual after fertilization occurs.
Mechanics of Meiosis
Use the various instructional materials available to you in the lab answer the following questions:
How many daughter cells are produced from one parent cell that undergoes meiosis?
If the parent cell contains 4 chromosomes, how many chromosomes will be in each daughter cell
after meiosis is complete?
Are the daughter cells haploid (1n) or diploid (2n)?
Are the daughter cells genetically identical to the parent cell (i.e., clones), or are the daughter
cells genetically different?
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Where does meiosis occur in a woman? Where does it occur in a man?
What process restores the diploid number of chromosomes for the next generation?
Meiosis and Gamete Formation in Lily Anthers
Meiosis occurs in the ovaries and anthers of flowering plants. The products of meiosis in the
anther (the male sexual organ of the plant) are the male gametes (sperm) of flowering plants. The
sperm are contained in the pollen of the plant. The products of meiosis in the ovary (the female
sexual organ of the plant) are the female gametes (eggs).
Look at the display of compound light microscopes (or the display on the television) showing the
progressive phases of meiosis. Draw the cells at each stage and answer the following questions.
In each field of view, there will be a number of cells undergoing meiosis; the nuclei of these cells
will be in different phases of meiosis. Look at the cell at the tip of the pointer to view the labeled
phase; if the microscope is not equipped with a pointer, look at the cell in the center of the field
of view to see the labeled phase. PLEASE DO NOT MOVE THE SLIDES OUT OF
POSITION. USE ONLY THE FINE FOCUS ADJUSTMENT.
First Meiotic Division
Prophase I: The nuclear membrane has disintegrated and the chromosomes are visible. At this
stage, are the chromosomes present as homologues (pairs), or are they unpaired?
Metaphase I: The chromosomes are arranged along the equator. What is the name of the array
of fibers by which they are attached to the poles of the cell?
Anaphase I: Two distinct groups of chromosomes are moving towards the two poles of the cell.
Are the chromosomes within each group paired or unpaired?
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Telophase I: The two groups of chromosomes have aggregated at the poles. A cell wall is
forming which will divide the cytoplasm into two cells, each with a group of chromosomes.
Although you cannot see it, each chromosome consists of two sister chromatids held together at
the centromere. How does the state of the chromosomes at this stage of meiosis differ from a cell
that has just undergone mitotic telophase?
Second Meiotic Division
Prophase II: Just as in mitotic prophase and in prophase I of meiosis, the chromosomes are not
very distinct again at this stage. Is this cell diploid or haploid at this point? Explain your answer.
Metaphase II: The chromosomes are again aligned along an equator, and a spindle connects the
sister chromatids to opposite poles. What is the name of the area on the chromatids to which the
spindle fibers are attached?
Anaphase II: The sister chromatids are now moving to opposite poles.
Telophase II: A cell wall is forming between the separated groups of sister chromatids. They are
losing their identity as distinct chromosomes and becoming uncondensed chromatin again.
Because of the plane of sectioning used to prepare this slide, you may only be able to see 2 cells.
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However, remember that 4 daughter cells have been produced from each original parent cell. Is
the genetic material within each daughter cell the same or different from the parent cell?
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Lab 8: Genetics and Inheritance
Introduction
Genetics is the branch of science that studies the nature of inheritance. Just as life on Earth is
organized and can be studied on a hierarchy of levels, so, too, can genetics be studied on a
number of levels. As you study genetics, try to ask yourself what level of organization is being
examined: molecular, cellular, species, or population? In the last lab, you examined genetics at
the cellular level; specifically study the movement of chromosomes during nuclear and cell
division. Today, at the organism level of organization, you will explore some of the human traits
which are determined by specific areas of DNA (referred to as “alleles”) on the chromosomes.
Genes and Alleles
Chromosomes are made up of genes. A given gene may exist in several alternative forms; each
form is called an allele. During the process of fertilization, each parent will contribute to the
offspring (the zygote at this point) one allele for each gene. Therefore, each individual has two
alleles for each gene (one from each parent). The alleles that each parent will contribute to the
offspring are determined during the process of meiosis and fertilization. Following fertilization,
if one allele masks the expression of another allele, we say that the expressed allele is dominant
over the other allele. The allele that is masked is called the recessive allele.
To illustrate the concept of different alleles, we will examine a simplified version of the eye
color character in humans. We will explain eye color as if only 1 gene is responsible; however,
geneticists now know that there at least 2 genes involved in eye color inheritance. The allele for
brown eye color is dominant over the allele for blue eye color. If an individual has one blue eye
color allele and the one brown eye color allele, he or she will have brown eyes. Since this
individual had two different alleles for the same character (eye color in this example), we say
that his/her genotype is heterozygous. The genotype of an individual refers to what genes or
alleles that individual actually possesses. We can symbolize this heterozygous genotype with the
letters “Bb”, where the capital “B” symbolizes the allele for the dominant trait (brown eye color)
and the “b” symbolizes the allele for the recessive trait (blue eye color).
When an individual has two similar alleles for the same trait, the genotype is homozygous.
There are two possible homozygous genotypes. One is homozygous dominant (“BB” for our eye
color example). The other is homozygous recessive (“bb”). Note that a person with brown eye
color could have either of two possible genotypes, “BB” or “Bb”. There is only one possible
genotype for a person with blue eye color, “bb”. The phenotype is the actual physical trait that
an individual expresses. The phenotype for “BB” or “Bb” is brown eye color. The phenotype
for “bb” is blue eye color.
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Human Genetics
Differences exist among humans in a number of easily observed traits. Your instructor will help
you identify which of the following traits you possess. You may also watch a video about
human genetic disorders.
Tongue Rolling: Tongue rollers carry a dominant gene R.
Widow’s Peak: A dominate gene W causes the hairline to form a distinct downward point in the
center of the forehead. Baldness will mask the expression of this gene.
Earlobe free: The inheritance of a dominant gene E results in the free or unattached earlobe. If
the lobe is attached directly to the head, the individual is homozygous recessive for the attached
allele “e”.
Non-Hitchhiker’s thumb: Some individuals can bend the last joint of the thumb backward at
about 45-degree angle. These individuals are homozygous for a recessive gene, but there is
considerable variation in the expression of the gene. We shall consider those who cannot bend at
least one thumb backwards about 45 degrees as carrying a dominant gene.
Bent Little Finger: A dominant gene cause the terminal bone of the little finger to angel toward
the four (ring) finger. Individuals whose little fingers are straight posses the homozygous
recessive condition.
Facial Dimples: The inheritance of cheek dimples is controlled by a dominate gene D. The
homozygous recessive condition lacks the ability to express facial dimples. To determine
whether or not you have dimples, smile.
Short Index Finger: Place your hand flat on a table and determine if your index (second) finger is
short in relationship to the length of your fourth (ring) finger. The gene for short second finger is
sex-influenced in its expression, being dominant in males and recessive in females.
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Make a class data table that includes the traits and the number of students in your class showing
the dominant and recessive phenotypes of each trait. Be sure to provide an appropriate title and
labels for the table.
Is the dominant trait always the most common?
Graph the frequencies with a frequency diagram. Make sure to label your table and graph
appropriately.
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Test Crosses:
Students should work in groups of 4. Each groups should turn in pages 60-63.
You will use colored straws to represent different alleles of a gene. The straws will be placed in
bags (or envelopes) and drawn out at random (representing the formation of games and
subsequent fertilization). The combination thus obtained represents the possible combination of
alleles in the offspring. The straws in the bags represent parental genotypes.
Part I. Into one bag, place two pink straws (this parent is homozygous for pink allele, P). Into
another bag place two orange straws (this parent is homozygous for orange allele, p). Draw one
straw from each bag. Pretend that this gene codes for flower color with pink dominant to orange.
Write down the resulting offspring’s genotype. Put the straws back and repeat this several times.
What offspring genotypes do you observe?
Are there any other possible genotypes from this cross?
What offspring phenotypes do you observe?
Are there any other possible phenotypes from this cross?
Part II. Monohybrid Cross: cross between individuals who are both heterozygous for one trait.
In each bag place one pink straw and one orange straw. Since this cross represents one trait
(flower color), use only one letter “p” to represent each straw: (PP = 2 pink straws; Pp = 1 pink
and 1 orange straw; pp = 2 orange straws). Draw one straw from each as above and record the
genotype. Put the straw back in the bag and mix. Repeat the process 50 times recording the
offspring’s genotypes. Write small and try not to use up all the space that is given in each cell
(you will use this again for a dihybrid cross).
For example, if on the first cross you pull 1 pink and 1 orange, write it in the table like this:
1 Pp
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Count up the number of each genotype. What genotypic ratio did you obtain?
If pink flower color is dominant to orange, what phenotypic ratio did you obtain?
What genotypic and phenotypic ratios would you expect to obtain (hint: use a Punnett square)?
How well do your actual results agree with what you expected? Explain.
Would your results be better if you did the cross 500 times? 5000 times? Explain.
Part III. Dihybrid Cross: a cross between individuals who are both heterozygous for two traits.
In this case, color of flower (as in Part II) and shape of seeds.
Using two bags, place one green and one yellow straw into each bag. The green (dominant) and
yellow (recessive) straws represent different alleles of a gene that codes for seed shape (round or
wrinkled). We will use the letter “G” to represent the alleles, and we will assume that round
(GG, Gg) is the dominant phenotype and wrinkled (gg) is recessive. We could simulate this
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dihybrid cross by drawing a straw from each of the two new bags (each containing a green and
yellow straw) and a straw from each of the two bags used in Part II (each containing a pink and
orange straw). However, since you have already drawn 50 times from the bags in Part II, you
can simulate a dihybrid cross by drawing only from the two new bags and putting the genotypes
next to the results of Part II.
For example, if the first three genotypes in the monohybrid cross look like this:
1 Pp
2 PP
3 pp
Simply add the results of new genotypes next to the previous one:
1 PpGG
2 PPGg
3 ppgg
Count up the number of each phenotype. What phenotypic ratio did you actually obtain in your
simulated dihybrid cross with the straws?
What phenotypic ratio would you expect from PpGg x PpGg (hint: use a Punnett square).
How well do your actual results agree with what you expected? Explain.
Would your results be better if you did the cross 500 times? 5000 times? Explain.
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Lab 9: Seed Germination Experiment
Introduction
Seed germination and seedling growth are influenced by many factors. Some of these are
physical factors of the environment in which the seed exists, including climate (i.e.,
temperature, light quality and intensity, and moisture availability), soil factors (fertilizer or
nutrient levels, acidity [pH], and salinity) and other physical stimulants or inhibitors (i.e., fire,
freezing, or abrasion of the seed coat). Other factors that may influence seed germination are a
result of the biotic (living) environment surrounding the seed. These include competition with
other organisms for water, space, and light, as well as allelopathy, the inhibition of plant growth
by chemicals produced by another species of plant.
The purpose of this lab is to gain experience with the technique and process of seed germination
and to introduce you to several standard methods of scientific data analysis and summarization.
The following materials are available for you to use in learning how to germinate seeds:
♦ seeds of several plant species
♦ plastic petri dishes
♦ paper towel or filter paper (to line the petri dishes)
One of the keys to most successful research projects is the selection of the experimental
organism. Early genetics experiments relied on Drosophila, the fruit fly. In hindsight, this was an
inspired choice. We don’t have such a lofty goal of establishing the favorite experimental
organism for your experiment. Instead, we want to introduce experimentation by giving you a
chance to become familiar with a variety of species. Then you can select one that you feel will
best help you investigate an experimental problem.
Seed Germination
The focus of the experiment that you will conduct for your lab research project will be seed
germination. You need to become adept at keeping the seedlings alive through their first critical
days of growth. Choose one of these 3 plant species to test how different environmental factors
(your experimental treatments) influence normal germination and growth.
Seed germination is simply the sprouting of the seed. It is initiated when the seed begins to
absorb water. Several environmental factors, such as temperature and light, can stimulate
germination. Seed germination ends when the embryo within the seed begins to grow or
elongate. You can easily see this because a radicle, or immature plant root, begins to grow out
of the seed. Soon after the radicle appears, a shoot will begin to grow out of the opposite end of
the seed. The shoot is that part of the plant, which usually grows above the ground; it is
comprised of a stem and leaves. The earliest stage of plant growth, which begins immediately
after seed germination, is called seedling growth. For your experiment, you will likely be
observing and recording both seed germination and seedling growth.
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Construct an Observation Table
On the following page, make a table in which you will record your seed germination and
seedling growth observations for each of the seeds you are sprouting. Be sure to make daily
observations and measurements. For each group of seeds, record the number of seeds which have
germinated, and measure the length of the radicle and shoot after germination. (Because the
radicle or shoot may be curved, you might contour a piece of thread or dental floss along its
curvature and then stretch the thread (or floss) along a ruler to determine a straight-length
measurement.) Try to make your measurements at the same time each day, so the time intervals
between successive measurements will be the same. Leave space in your table to note any other
changes you observe and to describe anything else you do, such as giving the plants additional
water. Be sure to bring your petri dishes with your plants back to lab!!!!
Resources
The following materials are available for you to use in an experiment on seed germination that
you will design and carry out at home. Select either an environmental or biotic factor which you
will vary during your experiment. Use your curiosity and creativity, and remember the best
experiment is simple and straightforward, one that provides easily quantified results.
♦ seeds of several plant species: radish (Rhaphanus sativus), marigold (Tagetes
erecta), lettuce (Lactuca sativa)
♦ plastic petri dishes
♦ paper towel to line petri dishes
♦ assorted chemicals (e.g., vinegar, bleach, fertilizer)
♦ plant material (e.g., leaves, spices) which may be allelopathic
♦ mortar and pestle, scissors, blender, for grinding plant material
♦ assorted glassware & balances for measuring volume & weight, respectively
♦ alcohol burner, razors, forceps, for burning or abrading seeds
♦ colored cellophane
In designing and carrying out your experiment, you may also want to consider using the
following equipment if it is available in your home:
♦ refrigerator
♦ dark cabinets (e.g., beneath a sink)
♦ microwave oven
♦ freezer
Designing an Experiment
The design of your experiment involves 5 steps. Follow these steps to outline your
experiment. Then check your design with the Instructor before you begin setting up your
experiment.
STEP 1: Decide what problem you want to investigate. Some examples of experimental topics
include “Effects of Temperature on Kidney Bean (Phaseolus vulgaris) Germination”; “Influence
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of Eucalyptus Extract on Seedling Growth in Mung Beans (Vigna radiata)”; “Simulated Acid
Rain Effects on Germination in Corn (Zea mays)”; and “Effect of Fire Exposure on Lima Bean
(Phaseolus lunatus) Germination”.
STEP 2: Write down the hypothesis that you will test. For example, if your topic were
“Simulated Acid Rain Effects on Germination in Corn (Zea mays)”, you might hypothesize that
increasing acidity (relative to the acidity of tap water) inhibits germination.
STEP 3: Decide on the details of your procedure:
1. Describe the experimental treatments for your experiment. Using the simulated acid rain
example, you might water one petri dish of corn seeds with pH 6 water, a second dish of
seeds with pH 5 water, and a third dish of seeds with pH 4 water. (Ask your Instructor for
help in mixing solutions.)
2. Describe the control for your experiment. In our simulated acid rain example, a petri dish of
corn seeds watered with tap water (pH ≅ 7) would serve as a control.
3. What will be the sample size (number of seeds) for each treatment and control? Remember
too few seeds may not give you good data due to bias in small sample sizes.
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4. List the steps involved in setting up and carrying out your experiment (your methods) and
list all types and amounts of seeds, supplies, equipment, and solutions you are using (your
materials). Be specific and descriptive so your Instructor can spot potential pitfalls and make
suggestions.
5. State the type of measurements or observations you expect to make in your research. Will
you be counting number of seeds germinated, measuring lengths of radicles, heights of
shoots, weight of new growth, number of days until germination begins, or what? How often
will you record observations? These measurements and observations will be your
experimental data.
6. What graphs or tables will you make to report your results (frequency, scatter, line, etc.)?
Be sure to include all of the parts of a table or figure.
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STEP 4. Make a prediction.
Write down your predicted results IF your hypothesis is correct. Using our simulated acid rain
example, you would expect that the greater the water acidity to which corn seeds are exposed,
the less is the frequency of germination.
STEP 5: When you have finished the design of your experiment, have your instructor check it
over. When your Instructor says “OK,” then start your experiment. Check out any items you will
need from the laboratory in order to conduct your experiment at home.
Discussion
At the end of one week of observation, write a discussion of your results. Was your hypothesis
supported by the data? Why or why not. How would you do this experiment differently in the
future? (You may pick a few nicely grown seeds and plant them into small pots to keep for
yourself.)
Some questions to think about:
1. What is germination? How did you determine when your seeds had germinated? How many
seeds germinated? Did they germinate all at once, one a day, or what pattern? How did you
record this data?
2. What is growth? Is it the same as germination? Where does one stop and the other start?
3. Where do these plants normally grow? Do they live in acid soils? Exposed to salt water?
4. What is already known about the effects of the experimental factor you were using? How
does acid or darkness or salt usually affect plants?
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Scientific Report Paper
You will write and turn in a few weeks later a scientific report paper detailing your seed
germination experiment. The report should convey your complete understanding of the
experiment that you conducted. A sample paper is given for you at the end of these instructions.
It should be written primarily in past tense. First person should be avoided. It should be
typed, double-spaced, and include the following sections, labeled, in this order:
1. Title of the report, your name, date, course name, and the name of the instructor should be on
the cover page. The title should be specific. For example: The effects of temperature
and pH on catechol oxidase activity. NOT: Enzyme Lab.
2. Abstract:
The abstract is a short passage (a paragraph) that summarizes the major points of the
paper: objectives, methods, results, and conclusions. It may be easiest to write the
abstract last, although it comes first in your paper. It must be informative but brief
and to the point.
3. Introduction:
The introduction should give the reader background information about your topic to
justify your experiment. It should explain the major objective of your experiment.
End your introduction with a statement of your hypothesis. Use references to find
background information and cite these references in the text at the end of the sentence
or paragraph (see below). You must directly acknowledge the source of any
material, ideas, or concepts that are not your own!! The failure to do so is
plagiarism!! If you use the author’s direct words, you must enclose his words in
quotes (“) and include a citation. However, you should use direct quotes sparingly.
Paraphrase the author’s ideas in your own words, and cite the reference at the end of
your sentence. Citations should follow one of the appropriate formats shown below
or see www.mla.org/style/sources.
4. Materials and Methods:
This section of your report tells the reader how you conducted your experiment, so
that he/she could repeat it if they wanted to (recall the importance of repeatability to
the Scientific Method). It should be written in complete sentences and paragraphs,
not lists, and in past tense. It should and identify the variables for the experiment
and specify how you made your measurements what controls you used.
5. Results:
The results section of the paper should summarize and illustrate your data. It should
be well organized and present the data in a logical order. You should include all of
your data in tables or figures which are properly labeled, and then describe these
results in the text and refer to the tables and figures. A table or figure by itself does
not constitute a results section.
6. Discussion and Conclusions:
The discussion should interpret your results: i.e. tell the reader what you think your
results mean. For example, do the data support your hypothesis? How or how not?
You may refer back to your data as evidence to support your conclusions. Address
the question of how your results are relevant to the topic of the experiment, i.e. the
“big picture”. Use references to find other similar experiments that have been
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7.
conducted and cite these references in the text (see below). Discuss how your results
differ or are similar to these other experiments. Discuss any possible sources of error
in your experiment.
Literature Cited:
The literature cited is like a bibliography, but it lists only those sources which you
have actually cited in your text. This should be the last page(s) of the report.
Arrange your references alphabetically by each author’s last name, and indent under
the first line. Leave 2 spaces between listings. Your report must cite at least five
references, which may include your textbook and lab manual. Encyclopedias and
dictionaries are not acceptable references.
Citing References in the text:
Generally, use the author’s last name and the year of publication.
for a work by one author:
…“sexual dimorphism in the species” (Jackson, 1976).
for a work by two authors:
… found to be of the heterozygous type (Jackson and Ard, 1988).
for a work by multiple authors:
… entirely due to the independent variable (Jackson, et al. 1982).
for an author whose name is used in the sentence:
… Jackson found similar results with his mice (1990).
for a web page or reference without a specific author, use the title and year:
… genetically altered mice that glow (Mice Genetics, 2001).
Listing References in the Literature Cited:
List the author first, then the year, the title, and publication information.
for a book:
Jones, C. W. and W. D. Billings. 1992. The Genetics of Fruit Flies. 2nd ed.
Wadsworth Publishing Company, New York.
for an article or chapter in an edited book:
Jackson, T. 1990. The effects of pH changes on saltwater aquaria. Pages 23-31
in H. H. Hobbs, ed. The Complete Aquarium. Yale University Press, New
Haven.
(NOTE: Hobbs is the editor, Jackson is the author.)
for an article in a journal or magazine:
Jenson, A. B. 1994. The diffusion of potassium permanganate molecules in water.
Science 70:457-459.
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(NOTE: Science is the name of the journal, 70 is the volume #, 457-459 are the
pages on which the article was found.)
for a personal web page:
Lancashire, Ian. Home Page. May 1, 1997.
http://www.chass/utoronto.ca:8080/ian/index.html.
for a professional web site without a specific author:
The Human Genome Project Information. Aug. 30, 1998
http://www.ornl.gov/TechResources/Human_Genome/home.html.
Some helpful hints of writing:
1. Make an outline. Outlines help to organize your thoughts and will limit redundancies.
2. Write simply and concisely. Say what you mean and avoid catch phrases.
3. Try to avoid starting sentences with: However, Therefore, Also, Yet, Then, And, Or, In my
opinion, I believe, I think, I feel, It also. Other words to avoid: thing, also, it, I believe,
surely, very.
4. Transition: Be sure to transition from paragraph to paragraph. This is not a grocery list.
Some common problems:
Too casual
Say for instance, a famous movie star wanted to be cloned, ok that’s cool but, what happens…
Too vague
I believe the human genome project will bring hope to the economic and medical future.
Exaggerated statement
This is a project studied by not only the United States, but by all, other countries, it is an
international project.
Run-on sentence – break items up into separate sentences or use commas.
Surely this information will become valuable by scientist selling this information or trying to
make money instead of helping people this technology will be abused.
Keep consistent with verb tense
This world wide research effort had the goal to analyze the human structure of the DNA and
knowing the location of one hundred thousand human genes.
Redundancy within the same sentence
Basically that’s how the human genome project works and hopefully later in the future we will
have…
Redundancies within the paper. Make statements about facts and your opinion only once.
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SAMPLE PAPER
The Effects of Temperature on the
Horseradish Peroxidase Enzyme.
Name
Date
Course
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ABSTRACT
Temperature is known to be an important factor in enzyme activity. In this study, the effect of
different temperatures on the activity of the enzyme peroxidase was determined using the
substrate guaiacol. A color change of the enzyme reacting with guaiacol was measured using a
spectrophotometer. The enzyme was subjected to four different temperatures: 250C, 350C, 450C
and 550C. Absorbance readings of the reaction were measured in the spectrophotometer over a
period of time of 60 seconds for each temperature. The different temperatures did have an effect
on the enzyme’s activity. The absorbance readings for 250C, 350C, and 450C were all very
similar, however, the reaction at 350C had the greatest rate of activity. The reaction at 550C had
the lowest rate of reaction. This shows that the optimal temperature for the enzyme peroxidase is
350C.
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INTRODUCTION
Enzymes are protein molecules which function as biological catalysts. They enable cells
to perform a multitude of chemical reactions very rapidly by lowering the energy of activation
required to initiate the reaction. In this process of speeding up the reactions, the enzymes are not
used up or chemically altered. They are able to be used over and over again in the cell. The
enzyme works by binding with the substrate, and then changing shape to cause the reaction to
occur with less energy and produce the product (Campbell et al. 1999).
An enzyme’s environment can affect the activity of the enzyme. Temperature, pH,
substrate concentration, and enzyme concentration can all influence the activity of an enzyme.
Since enzymes are proteins, their secondary and tertiary structure is important in their function.
If the hydrogen bonds which determine this structure are destroyed, the enzyme will denature, or
lose its shape, and no longer function. Denaturation can be caused by extreme temperature or
pH (Campbell et al 1999).
Substrate and enzyme concentration can also influence enzyme activity. Enzyme activity
will generally be higher with higher substrate concentration, until the enzyme becomes saturated
(all of the enzyme molecules are being used). Then, to increase activity, the enzyme
concentration must be increased (Floyd 2001).
Enzyme activity can be determined by measuring the amount of product that is produced.
If the product of the reaction is a different color than the substrate, then this color change can be
measured in a spectrophotometer. This device measured the amount of light that is absorbed by
a solution. The darker the color of the solution, the more light will be absorbed. The reaction
mixture can be placed in the spectrophotometer and the absorbance recorded as the reaction
occurs.
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The enzyme peroxidase can be easily derived from horseradish. Peroxidase in the
presence of hydrogen peroxide reacts with the substrate guaiacol. Guaiacol can be derived from
the resin of a tree. The reaction of guaiacol with peroxidase causes a color change from reddishbrown to clear. This color change can be monitored in a spectrophotometer to observe the rate of
reaction (Floyd 1999).
To find the optimal temperature conditions for peroxidase, the enzyme was subjected to
four different temperatures. It was hypothesized that room temperature, 250C, would produce
the greatest enzyme activity, and therefore the greatest color change as measured by absorbance
in the spectrophotometer.
MATERIALS AND METHOD
Four test tubes were prepared with 1 mL of substrate (5mM guaiacol and 2% hydrogen
peroxide) and 1mL of buffer (citric acid-disodium phosphate at pH6). One test tube was kept at
room temperature (approximately 250C). The other three test tubes were placed in three separate
water baths (350C, 450C and 550C) and allowed twenty minutes to equilibrate. The
spectrophotometer was blanked at 470nm with the room temperature test tube of substrate and
buffer. Then, 0.l mL of enzyme (lxl0 M peroxidase) was measured with a pipette and quickly
added to the room temperature test tube and it was immediately placed into the
spectrophotometer. The readings from the spectrophotometer were recorded in five-second
intervals for a period of one minute. The procedure was repeated for the other 3 test tubes. The
absorbance readings were then graphed.
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RESULTS
The test tube at 250C had the highest final absorbance of 0.123 (see Figure 1). This
reaction also had the most change over the one minute period, from 0.039 to 0.123, however the
initial rate of change was 0.00165 nm/sec. The test tube at 350C had a final absorbance of 0.115
and a total change of 0.097. This reaction had the greatest initial rate of change 0.0018 nm/sec.
The 450C test tube reached a final absorbance of 0.099 and had a total change of 0.047, but the
initial rate of change was 0.0017 nm/sec. The 550C test tube had a final absorbance of 0.052 and
a total change of 0.008. The initial rate of change was 0.00087 nm/sec.
Figure 1. The absorbance readings of peroxidase at different temperatures.
0.14
Absorbance 470
0.12
0.1
25 C
35 C
45 C
55 C
0.08
0.06
0.04
0.02
0
0
5
10
15
20
25
30
35
40
45
50
55
60
65
Time (seconds)
DISCUSSION AND CONCLUSIONS
This experiment shows that temperature does have a significant influence on the activity
of enzymes. The results for 250C, 350C, and 450C were all very similar, however, the reaction at
350C had a slightly greater rate of activity. This indicates that 350C is the optimal temperature
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for the horseradish peroxidase enzyme, contrary to the original hypothesis. This indicates that
horseradish should be stored in cool temperatures to prevent breakdown. The test tube at 550C
showed the least amount of activity. At this temperature, the enzyme must have begun to
denture and no longer be able to function.
An experiment using soybean peroxidase (SBP) found the SBP to still function at 900C.
The article states that SBP is substantially more thermostable than horseradish peroxidase
(McEldoon and Dordick 1996). Another experiment using peroxidase purified from rice hulls
found that it is also stable at higher temperatures (Ryu and Kim 1997). Human enzymes usually
have an optimal temperature of approximately 350C to 400C, close to human body temperature
(Campbell, et al. 1999). However, horseradish peroxidase is not a human enzyme, nor is it
soybean peroxidase. This experiment shows that the optimal temperature for horseradish
peroxidase is 350C and that its function begins to deteriorate at temperatures of 550C.
Although this experiment was performed very carefully, there are two major sources of
error which may have affected the results. The enzyme may not have been measured accurately
in the test tubes. The small amount of enzyme used, 0.1 mL, was difficult to measure by hand
pipetting. An automatic micropipette would have been more accurate. Also, the enzyme may
not have been mixed with the substrate very well. The mixing was done by inverting the test
tube before it was inserted in the spectrophotometer. This had to be done quickly because the
reaction begins immediately, but this quick mixing may not have been complete mixing. This
experiment should be repeated many times to insure accuracy of the conclusions.
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LITERATURE CITED
Campbell, N.A., J.B. Reece, and L.G. Mitchell. 1999. Biology. 5th ed. Benjamin Cummings,
California.
Doordick, J.S. and J.P. McEldoon. 1996. Extraordinary Thermal Stability of Soybean
Peroxidase. Biotechnology Program 12:555-558.
Floyd, J.W. 2001. Biology 171 Laboratory Manual. Leeward Community College, Pearl City,
HI.
Ryu, K., and Y. Kim. 1997. Activation by Organic Solvents of an Alkaline Thermostable
Peroxidase / Partially Purified From Rice Hulls. Biotechnology Letters 18:1019-1022.
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Lab 10: Microevolution and the Hardy-Weinberg Equilibrium
NOTE: You will need a calculator for this lab.
Introduction
Microevolution occurs over a relatively short period of time. Microevolution is a change in the
gene pool of a population over a succession of generations. The gene pool is the sum total of all
the alleles (forms of a gene) in a population. It is possible to observe microevolution within your
lifetime. You have already been witness to it, even though you may not be aware of it! Every
new breed of flower developed by humans or every new breed of dog created demonstrates
microevolutionary change. Of course, this type of evolution is artificial since humans are
responsible for it. Microevolution occurs in nature, too. Any type of genetic change in a
population of organisms that gives them some sort of adaptive advantage in their environment is
microevolution. For example, the many different plants and animals that originally colonized the
Hawaiian Islands have adapted to the unique environment of Hawai’i. Many of them only
remotely resemble the parent population from which they descended, and are now classified as
unique species.
Evolution can most accurately be defined as changes in gene frequency within a population over
time. Because it is difficult to visualize gradual genetic changes within large populations,
scientists often used mathematical models for the purpose of ordering and directing thinking
about such elusive processes. These models are mental tools that in most cases facilitate analysis
of biological problems. Models are always oversimplifications of the actual situation. However,
if the model should closely approximate the real situation, the scientist might better explain the
situation in simple terms. This often leads to a better understanding of the actual natural process.
The model that explains changes in gene frequency within a population (evolution) is called the
Hardy-Weinberg Equilibrium. The concept of the model was first proposed in 1908 by G.H.
Hardy, and English mathematician, and G. Weinberg, a German Physician. The HardyWeinberg equilibrium states that the gene and genotypic frequencies of any trait in a large,
randomly mating population (and in the absence of mutation, natural selection, migration, and
other disturbing factors) will remain unchanged from generation to generation. Such a
population is said to be in genetic equilibrium. In simpler terms, the model predicts that
genotypic expression of a single trait (homozygous dominant, AA; heterozygous, Aa; and
homozygous recessive, aa) will be produced with unchanging frequency in an equilibrium
population. Such a population is not evolving with respect to the given trait. Although no natural
biological population ever meets all the conditions of the “ideal” Hardy-Weinberg population,
such a model population can serve as a base line from which actual change in populations can be
measured and from which the rate of genetic change can be mathematically computed.
The equation for the Hardy Weinberg Equilibrium is p2 + 2pq + q2 = 1.00.
p is the frequency of one allele (A)
q is the frequency of the other allele (a)
Since there are only two alleles, p + q = 1
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The condition of sickle-cell anemia may provide a suitable example of how the Hardy-Weinberg
Equilibrium may be applied. It is known that the frequency of the sickle cell allele (s) is 20% in
some African populations. Therefore, the frequency of the normal allele (S) is 80%. So p = 0.80
and q = 0.20. Using the Hardy Weinberg equation, we can determine the frequency of each
genotype as well.
p2 is the frequency of homozygous dominant individuals(SS)
2pq is the frequency of heterozygous individual (Ss)
q2 is the frequency of homozygous recessive individuals (ss)
So
p2 = 0.82 = 0.64 SS, 2pq = 2 (0.8) (0.2) = 0.32 Ss, q2 = 0.22 = 0.04 ss
In fact, 4% of individuals in these populations are homozygous recessive (ss) and are thus
afflicted with sickle-cell anemia.
If we assume that this population is in genetic equilibrium, the Hardy-Weinberg Equilibrium
predicts that the genotypic frequencies will remain unchanged. In practice, however, gene and
genotypic frequencies in natural populations rarely remain stable. In the example of sickle-cell
anemia, homozygous recessive (ss) individuals rarely survive to reproduce and the s allele is
transmitted to future generations with a much lower frequency than the S allele. This differential
reproductive success can have a profound effect on genetic equilibrium over many generations.
A number of other factors can also disturb the genetic equilibrium of alleles in the gene pool.
The Hardy-Weinberg Equilibrium, with all its predictive value, holds only for hypothetical
populations in which:
1. The sample size is infinitely large. There is no genetic drift, random changes in a
population.
2. There is no immigration or emigration of individuals. There is no gene flow
between populations.
3. Mutation does not occur.
4. Mating is random.
5. All zygotes survive to reproduce with the same frequency; i.e. there is no natural
selection.
However, the Hardy-Weinberg Equilibrium does provide a workable model from which the rate
of evolution can be measured and even predicted. The model provides a simple method to
measure causes of evolution, including genetic drift in small isolated populations, gene flow,
mutation, non-random mating, and natural selection.
Procedure:
Students should work in groups of 4. Each group should turn in pages 81--85.
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This exercise will simulate natural selection resulting from the behavior of predators. The
population you will be worked with is composed of colored beads. Red beads in this population
represent individuals that are homozygous for the red color allele (RR). Pink beads are
heterozygotes (Rr), and large clear beads represent individuals homozygous for the allele for
clear color (rr). (Or you may have blue (BB), light blue (Bb), and clear (bb) beads). The beads
exist in a “pond” (plastic bowls) filled with small clear beads that represent the water and other
part of the environment. The alleles in our population are incompletely dominant, so
heterozygotes have an intermediate phenotype. The total number of alleles in a population of 80
individuals is 160 (alleles in each individual).
p = red allele frequency (R), q = clear allele frequency (r)
Exercise A: Natural Selection
1. Place 20 red beads, and 40 pink beads, and 20 large clear beads into the bowls filled with
small clear beads.
2. One student will act as the predator. After the beads are mixed, the predator searches the
pond and removes as many prey items as possible in 30 seconds. In order to model the
handling time required by real predators to find and eat their prey, you must search for and
remove the beads with chopsticks or a pair of long forceps. The predator’s fitness is how
many prey it can capture. The predator is not picky. It eats the first prey it sees. So, pick up
the first bead you see as fast as you can. You cannot cheat and search for only one color
bead.
3. Because some of the beads blend into the environment, the proportion of beads captured may
not be the same as the original proportion. Subtract the number of each color bead captured
from the number you started with to determine the number of each type of bead remaining
the pond. Use these remaining numbers to calculate the frequencies of the alleles remaining
in the population. Record your data in a table.
For example: If the predator removes 15 red beads, 10 pink beads, and 5 clear beads. This
means that 5 red (RR), 30 pink (Rr), and 15 clear (rr) beads remain in the artificial pond. (WHAT
REMAINS IN THE POND IS WHAT IS IMPORTANT BECAUSE THEY ARE THE SURVIVORS THAT
CONTRIBUTE GENES TO THE NEXT GENERATION -- THAT IS, YOU DIDN’T KILL THEM) There
are a total of 50 “organisms” left, so there are a total of 100 alleles left in the population (each
individual has two alleles). Therefore, the frequency of the clear allele (q) in the surviving
population is:
q = 2 (# of rr survivors) + # of Rr survivors
2 (total number survivors)
= 2 (15) + 30 = 0.6
2(50)
and
p = 1 – q = 0.4
There are 15 clear beads each providing 2 r alleles (2 x 15); 30 pink beads, each providing 1 r
allele (1 x 30), all divided by the total alleles in the population, 2 per individual (100).
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4. Use these new values for allele frequencies (p and q) and the Hardy-Weinberg formula to
calculate the number of red (p2), pink (2pq), and clear (q2) individuals for the next
generation. Remember, p2 + 2pq + q2 = 1.00, so p2 is the frequency of the red individuals
(RR), 2pq is the frequency of pink individuals (Rr), and q2 is the frequency of clear
individuals (rr).
Example: p2 = 0.42 = 0.16, 2pq = 2 (0.6) (0.4) = 0.48, q2 = 0.62 = 0.36
5. Assume the population reproduces to the original size (80 individuals) and the individuals
live only one generation so that only the offspring will be the next generation. Calculate
what proportion of the 80 individuals in the next generation will be of each genotype.
Example: p2 x 80 = 0.16 x 80 = 13 red individuals in the next generation
2pq x 80 = 0.48 x 80 = 38 pink individuals
q2 x 80 = 0.36 x 80 = 29 clear individuals
6. Remember how many beads of each color are left in the pond (the survivors) and add (or
subtract) enough beads to your pond so that the number of each color matches your new
calculations for the next generation.
7. Repeat steps 2 – 6 for 5 or 6 more generations. A different student should be the predator in
each generation. Try to catch the prey as fast as you can. Between each generation calculate
the new allele frequencies and adjust your pond population. Record your data in the tables.
Table 1.
Red Beads (RR)
Pink Beads (Rr)
Clear Beads (rr)
Totals
Generation # Born # Survivors # Born # Survivors # Born # Survivors Born
1
20
40
80
20
2
80
3
80
4
80
5
80
Table 2.
Generation
1
2
3
4
5
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p
q
p2
2pq
Survived
q2
81
Calculations:
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Make a graph to show the change in the number of clear individuals in the population over
generations.
Make a graph of the frequency of clear alleles (q) and red alleles (p) in the population over
generations.
How do the frequencies change? Can you explain the change?
If you had started with a pond filled with small red beads, how would the allele frequencies have
changed?
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Exercise B: Gene Flow
1. Add or subtract beads to return the population to 20, 40, an 20, as in Exercise A.
2. Begin predation for 30 seconds as before. After the predator has eaten, add 5 new red beads
to the population before the allele frequencies are calculated. This represents migration from
another population. Now calculate the new allele frequencies and determine how many
individuals to add to the pond for the next generation.
3. Do this for 2 or 3 more generations. Make a table to record your data.
How does migration influence the effectiveness of natural selection?
How would migration have influenced the allele frequencies if clear individuals instead of red
had migrated into the population?
Exercise C: Genetic Drift
1. Separate out all of the beads and count out 20, 40, and 20 again, but do not mix the beads into
the pond. Calculate q for this initial population.
2. One student in the group should, without looking, pick ten beads from the population at
random. These are the survivors of a natural disaster that randomly kills everyone except the ten
you picked. (Or the ten you picked can go off and start a new population in a new area.)
3. Calculate the allele frequencies for the new population of the ten you picked.
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How do these frequencies compare with the initial population? Why are they similar or
different?
What are the two types of genetic drift?
Exercise D: Non-random Mating
What would happen to the initial population (20, 40, 20 as in Exercise A) if all red individuals
only mated with red individuals, pink only mated with pink, and clear only mated with clear?
This is an example of non-random mating. Assume there are equal numbers of males and
females of each color, and that each pair produces four offspring. How many of each phenotype
will be present in the next generation? (Remember pink pairs will produce 1 red, 2 pink, and 1
white on average.)
How will the allele frequencies compare to the initial population as a result of non-random
mating?
How will the number of individuals of each genotype (color) compare to the initial population?
Exercise E: Mutation
What would happen to the allele frequencies in the initial population (20, 40, 20) if a mutation
produced one gray individual?
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Lab 11: Macroevolution
Introduction
The theory of evolution attempts to explain how life began, and how life has become so diverse.
Evolution encompasses all the changes that have transformed life on Earth from its earliest
beginnings to the diversity that characterizes it today. It includes the past transformation of
organisms from unicellular to multicellular complexity, as well as modern species’ “descent with
modification” from prior living things. Evolution is the study of how life began and how life
changes.
Scientists have proposed many theories about the rates, causes, and patterns of evolution.
Information about the evolutionary history and relatedness of organisms has come from fossils,
embryology, comparative anatomy, physiology, and biochemistry. An understanding of the
“how” of evolution (the mechanisms of evolution) can be gained, in part, by observing genetic
changes between generations of populations.
Evolution can be viewed on two main scales: macroevolution and microevolution.
Macroevolution is evolutionary change on a grand scale. It involves the transformation of
organisms from one type to another, such as from a single-cell organism into a multi-cellular
organism, or the transformation of a reptile into a bird. Macroevolutionary changes require
millions and even billions of years. Specific evidence that points to macroevolution includes
fossils, anatomical and biochemical comparisons, and embryology. In this lab you will examine
some of the types of evidence that scientists use to support the theory that evolution has occurred
on Earth.
Microevolution occurs over a relatively short period of time. Microevolution is a change in the
gene pool of a population over a succession of generations. The gene pool is the sum total of all
the alleles (forms of a gene) in a population. It is possible to observe microevolution within your
lifetime. You have already been witness to it, even though you may not be aware of it! Every
new breed of flower developed by humans or every new breed of dog created demonstrates
microevolutionary change. Of course, this type of evolution is artificial since humans are
responsible for it. Microevolution occurs in nature, too. Any type of genetic change in a
population of organisms that gives them some sort of adaptive advantage in their environment is
microevolution. For example, the many different plants and animals that originally colonized the
Hawaiian Islands have adapted to the unique environment of Hawai’i. Many of them only
remotely resemble the parent population from which they were derived, and are now classified as
unique species. In today’s lab you will also explore some examples of Hawaii’s unique
evolutionary history.
Recognizing that unlike species have likely evolved from a common ancestor and that all forms
of life probably stem from the same remote origin, biologists naturally want to understand the
relationship between the species alive today and to know from what sorts of ancestors they have
descended. In other words, they want to know the evolutionary history of the various forms of
life. Such evolutionary history is called phylogeny. (see Figure 1)
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When biologists set out to reconstruct the phylogeny of a group of species that they think are
related, they face a Herculean task. Usually, they have before them only the species living today.
They cannot observe their phylogenetic history. In most cases, they can never know with
certainty exactly what that history was. To reconstruct it as closely as possible, they must make
educated inferences based on observational and experimental data that appear relevant, if only
remotely so. Those data can usually be interpreted in several different ways, and only
experience and good judgment can help the biologists choose among them.
The usual procedure in attempting to reconstruct phylogenies is to examine as many different
characteristics of the species in question as possible and to determine in which characters they
differ and in which they are alike. The assumption is that the differences and resemblance will
reflect, at least in part, their true phylogenetic relationships. Ordinarily, as many different types
of characters as possible are used in the hope that misleading data from only single character will
be detected by a lack of agreement with the data from other characters.
Evolution typically occurs in one of two different pedigree modes. Sequential (non-branching)
evolution occurs in a linear fashion, minimizing the radiating effects of adaptation. In divergent
(branching) evolution, however, more diversification occurs in an environment, facilitating
larger numbers of species.
Figure 1.
D
↑
C
↑
B
↑
A
SEQUENTIAL EVOLUTION
D
G
K
C
↑
B
R
S
Q
F
A
DIVERGENT EVOLUTION
In extreme cases, separate stocks are so similar that it is difficult to establish their independent
ancestry. Such similar groups may be the product of parallel evolution and have more than one
ancestral stock. These groups are called polyphyletic, whereas groups descended from a single
ancestral stock are called monophyletic. The mammals are thought by some evolutionists to
have evolved from as many as seven different ancestral reptilian stocks, making the mammals
polyphyletic. Amphibians, however, are thought to have evolved from a single lobe-finned fish
ancestor, thus exhibiting monophyletic origin.
Finally, the fossil record has provided sufficient trends in evolution for us to hazard a few
generalizations. Understand that these are by no means “laws of nature” but rather tendencies
that we have observed in analyzing life’s history.
1. Life has existed for a long time, two thirds the age of the earth
2. Organisms have continuously changed as a result of genetic variation, and the chemical,
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biological, and geological parameters of their environment selecting only a few survivors.
3. Evolutionary trends appear to be from:
A. Simple to complex
B. Unicellular to multicellular
C. Aquatic to terrestrial
4. While more complex organisms have developed, simpler forms still persist.
5. The chronology of the fossil record parallels the patterns of embryological development of
modern forms (“ontogeny recapitulates phylogeny”).
6. No species which has become extinct ever reappears
7. Extinction is the rule – survival is the exception.
MACROEVOLUTION
Fossil Evidence
A fossil is any record or remains of an organism that lived in the geologic past. Fossils are
usually formed when an organism is covered by sediments that harden into sandstone, slate,
mudstone, or flint. Organisms also fossilize when they are buried in volcanic ash or entombed in
tar or tree sap (amber). Some fossils are impressions or molds of the organism left in the rock.
Footprints, or other trails, are an important type of fossil. Other fossils are the result of
petrification which occurs when the hard parts (and sometimes the soft parts) of an organism are
replaced over time by minerals.
Examine the fossil collection and charts on display. Fill in the information requested in the
following table for 4 of the fossils.
Fossil
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1st appearance of
group on Earth
(years ago)
Period of
greatest
abundance
Years since
greatest
abundance
Extinct?
Similar species
still in existence
89
Anatomical Evidence
Structural similarities between organisms can be clues to their relatedness, or common ancestry.
Similarity in characteristics resulting from common ancestry is known as homology, and these
anatomical signs of evolution are called homologous structures. For example, the same skeletal
elements make up the forelimbs of humans, frogs, bats, porpoises, and horses, although these
appendages have very different functions. Evolution is a remodeling process in which anatomical
structures that functioned in one capacity become modified as they take on new functions.
Not all similarities are inherited from a common ancestor, however. Species from different
evolutionary branches may come to resemble one another if they have similar ecological roles
and natural selection has shaped similar adaptations. This is called convergent evolution.
Similarities due to convergence are called analogous structures. For example, the wings of
birds and the wings of insects are analogous, as they are built from entirely different structures
and they evolved independently.
Vestigial structures are also clues to relatedness. Vestigial structures serve no apparent purpose,
but are homologous to functional structures in related organisms. For example, your appendix (a
dead-end intestinal sac about the size of your little finger) has no critical function, but in some
herbivorous (plant-eating) mammals, it is a large sac where partially digested food is stored. As
another example, some snakes have internal, vestigial leg bones, which are historical remnants of
the ancestral reptiles from which they evolved.
Look at the plants on display. The spines of cacti are actually highly modified leaves, while the
thorns of the crown-of-thorns plant are modifications of the stem. Are these structures
homologous or analogous?
Can you think of another vestigial structure that humans have besides the appendix? What
function might it have served in our mammalian ancestors?
What mammals would you expect to have vestigial leg bones?
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Embryological Evidence
A study of embryonic development provides clues to the evolutionary past. Related organisms
show similarities in their embryonic development. At one point during your prenatal
development, you had gill slits. In fact, all embryos of vertebrates (animals with backbones)
develop gill slits or pouches. Yet gill slits are functional only in the adults of aquatic vertebrates,
not of land-dwellers. Why do retain gill slits? Gill slits are cellular scaffolding. The removal of
this stage from our embryonic development could change the arrangement of tissues around the
slits and affect development of other structures. Gill slits are an example of the characteristics of
embryos that reveal our kinship with other members of our phylum.
Examine the pictures of vertebrate embryos at comparable stages of development. List three
similarities in the structure of embryos.
Would you expect the embryo of a horse to more closely resemble the embryo of a human or the
embryo of a bird? Why?
Fossil Puzzles
Work in groups of 4 for this activity. It is the purpose of this laboratory exercise to give you the
opportunity to view evidence of evolutionary change. Given the pieces of this puzzle and a few
rules to follow, you should be able to assemble some interesting speculations as to how evolution
may have occurred.
A prominent paleontologist uncovered a fossil bed that was rich in microfossils and invertebrate
fossils heretofore undiscovered! Careful analysis has revealed that this fossil bed represents an
ancient microhabitat, which has no modern counter part. Fossils have been “lumped” into three
categories based on morphology: Puzzle A, B, C. It is thought that each puzzle represents a
particular evolutionary phylogeny. Your job is to determine the “correct” phylogeny based on
the characters of those forms, which appear to represent the ancestral condition and those which
appear to represent the derived condition(s). Keep in mind that evolution usually proceeds from
simple to complex, but also some structures may become vestigial. Draw the overall shape of
the phylogenetic trees that you assemble, and the organism at the beginning and end of each
branch. You don’t need to draw every picture. Be able make a convincing argument for the
reasons you placed the fossils in the order you did. You should now have an appreciation for
paleontologists!
Puzzle A
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Puzzle B
Puzzle C
Phylum Arthropoda
No other animal group had undergone an adaptive radiation in the magnitude of this group.
More than 80% of the animal species of the world are classified as arthropods. All arthropods
have an exoskeleton, body segmentation, and jointed appendages. The appendages which will be
the focus of our investigation.
It is generally believed that the ancestral stock of arthropods was distinctly segmented, much like
an earthworm, cut with fanlike jointed swimming appendages on each segment. Trilobites
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might serve as a model of such an ancestor as they were abundant in the Cambrian and
Ordovician Seas becoming extinct at the end of the Paleozoic Era; they represent our earliest
arthropod fossils and over 3,900 fossil species have been described to date.
Observe the trilobite specimen in the fossil collection.
One certain theme in the evolution of the arthropods is the differentiation and specialization of
the appendages. Unlike the trilobites, modern arthropods have different appendages on different
parts of their body, maximizing versatility while minimizing repetition. Primitive forms, such as
the horseshoe crab, have less versatile appendages and are similar to trilobites in the receptive
morphology of each appendage.
Appendages have differentiated in many arthropods to form mouth parts, walking legs,
swimming appendages, wings, and reproductive structures (e.g., the ovipositor of a grasshopper
is adapted for the depositing of eggs into an underground nest). In the table below, check off (√ )
which adaptations are apparent in each group. Place an asterisk (*) by those that you think are
particularly advanced (e.g., wings in insects, walking legs in millipedes).
Centipede/
Millipede
Grasshopper Crayfish
Spider
Horseshoe
Crab
Antennae
Walking Legs
Swimming
Appendages
Mouth Parts
Wings
Body
segmentation
Contrast the diversification of appendages above to those of the trilobite.
Based on the degree of diversification of appendages, sketch a phylogenetic tree for the
following arthropods: centipedes, millipedes, crustaceans, insects, trilobites, arachnids, and
horseshoe crabs. In other words, try to put these animals together in the same manner as you
constructed your fossil-puzzle phylogenetic tree.
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Looking over your suggested phylogeny, what seems to be the evolutionary tendency regarding
segmentation? (That is, as you proceed from the ancestral stock to more derived forms, what
change occurs with respect to segmentation?)
EVOLUTION OF HUMANS AND OTHER PRIMATES
Observe the display of skulls and/or photos of primate skulls.
Describe two features that these skulls have in common.
Describe two differences between the modern human skull (Homo sapiens) and the gorilla skull.
Look at the evolution of humans: Do you see any trends from the skulls of Australopithecus,
Homo habilis, Homo erectus, Homo sapiens neanderthalensis, and Homo sapiens sapiens.
What are the time differences (in 1000 of years) between the emergence of Australopithecus,
Homo habilis, Homo erectus, Homo sapiens neanderthalensis, to Homo sapiens sapiens.
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In terms of the Geological time scale, what percentage of the time since the Precambrian period
(600 million years ago) has Homo sapiens walked the earth?
What percentage of time since the first mammals are found in the fossil record (about 170
million years ago) has Homo sapiens walked the earth?
EVOLUTION IN HAWAII
The Hawaiian Islands are the most isolated island groups in the world. The distance from
Hawaii to the nearest continent (North America) or to the nearest archipelago (the Marquesas) is
more then 2000 miles. Due tot such remoteness, very few organisms arrived on their own to
colonize the volcanic islands as they emerged from the ocean. Those that did successfully
colonize and establish themselves in Hawaii were reproductively isolated from their ancestral
population and evolved into distinct species, many of which are unique or endemic to Hawaii.
The opportunities for evolutionary studies in the Hawaiian islands are unique. Nowhere else in
the world can one find such a rich “natural laboratory” in close proximity to modern university
and museum facilities. We will focus on two causes of microevolution: the founder effect and
adaptive radiation.
Founder effect: the colonization of a location by only one or a few individuals, resulting in loss
of genetic variation from subsequent populations.
Adaptive radiation: the evolution, from a common ancestor, of a number of species which are
specialized for survival in diverse environments.
Adaptive Radiation in Hawaiian Birds
The Hawaiian honeycreeper subfamily Drepanidinae is endemic to the Hawaiian Islands.
Originally, this group of birds contained approximately 29 species. However, since their
arrival humans have cleared large portions of the native forests and introduced numerous
alien plant and animal species. These compete with native species for food and habitat.
Introduced diseases and predators have also taken their toll. Today, 9 honeycreeper
species are extinct and 13 others are on the Endangered Species List.
The Hawaiian honeycreepers are a prime example of adaptive radiation. Based on
recent mitochondrial DNA evidence, it is estimated that 2 to 3 million years ago a
pregnant finch colonized the Hawaiian Islands. Its descendants took advantage of a
variety of habitats, and eventually a wide array of species evolved, each specialized for
its particular niche (a specific habitat and functional role in the ecosystem). Bill shape
and size are adaptations to feeding habits. Differences in bill form, as exemplified by the
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slender, curved bill of the nectar-feeding ‘i’iwi and the short, stout bill of the seed-eating
palila, are good examples of the changes brought on by adaptation to a very specific
environment.
Observe the poster showing the bills for the different Hawaiian honeycreepers. Write
hypotheses about what type of food the bill of each species is adapted for obtaining.
Check your hypotheses with your Instructor.
Birds:
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
I’iwi
Apapane
Akepa
Maui parrotbill
Grosbeak finch
Hawaii mamo
Crested honeycreeper
Kauai akialoa
Common amakihi
O’u
Ninoa finch
ula-oi-howane
Akiapola’au
Kauai creeper
Po’ouli
Food choices:
a)
b)
c)
d)
e)
f)
Flower buds or blossoms
Flower nectar
Fruits (fleshy and juicy, or hard and dried)
Seeds
Land snails
Insects (adult or larvae)
Hint: Insect larvae generally are embedded in tree bark; mature insects usually
can be found crawling on the surface of a tree or flying through the air.
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Lab 12: Plant Diversity
Introduction
The life cycle of plants is called alternation of generations: the gametophyte generation
alternates with the sporophyte generation. The haploid gametophyte produces haploid gametes
by mitosis, which unite in fertilization and grow into a diploid sporophyte, which produces
haploid spores by meiosis, which grow into a gametophyte.
Make careful drawings and notes during this lab. There will be a lab practical quiz next week!
Mosses
In the mosses, the gametophyte generation is dominant, and the sporophyte grows attached to it.
The sperm produced by the gametophyte must swim to the egg cell to fertilize it and produce a
sporophyte. Mosses are dependent on at least a small amount of water in the environment for the
sperm to swim through.
Observe the specimens of mosses in the lab. Which part is the gametophyte and which part is
the sporophyte? Where are the spores produced? Observe the Moss poster in the lab. Draw and
label a moss.
Mosses do not have vascular tissue to transport water though the plant; therefore they must live
in moist environments and remain small and close to the soil where the water is found. Mosses
also do not have true roots to absorb moisture out of the soil. They do, however have small rootlike structures called rhizoids. Do you see any rhizoids on the moss specimens? Label them on
your drawing.
Another group of plants related to mosses is the liverworts. The gametophyte of these plants is
a flattened tissue that grows along the ground. Observe the specimens of liverworts in the lab.
Ferns
Ferns are plants that have evolved a dominant sporophyte generation. They also have vascular
tissue and roots to transport water and so can grow larger and tolerate drier environments than
mosses. But the sperm produced by the gametophyte still must have a little bit of water to swim
through to fertilize the egg.
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Observe the fern sporophytes in the lab. Where are the spores produced? Draw and label a fern
sporophyte.
Observe a slide of a fern gametophyte. What color and shape is it? Observe the Fern poster in
the lab. Draw a fern gametophyte.
There are other groups of plants similar to ferns often called the fern allies. These include, whisk
fern (Psilotum), club mosses (Lycopodium), and horsetails (Equisetum).
Observe the specimen of whisk fern. It does not have leaves. How does it photosynthesize?
Where are the spores produced? Draw and label a whisk fern.
Observe the specimen of club moss. Where are the spores produced? Draw and label a club
moss.
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Observe the specimen of horsetail. Horsetails and club mosses were dominant on Earth during
the time of the dinosaurs. Now there is only one living genus of horsetails, Equisetum. Where
are the leaves? Where are the spores produced? Draw and label a horsetail.
Gymnosperms
Gymnosperms are plants that have evolved seeds for reproduction instead of spores.
“Gymnosperm” literally means “naked seed”, because the seeds are borne in open cones (rather
than in closed fruits in the angiosperms). Gymnosperms have also evolved pollen grains to
carry their sperm through the air, rather than having to swim. This allows gymnosperms to
reproduce independently of water in the environment, and to live in much drier places.
The most common gymnosperms today are the conifers (pines, spruces, firs). Observe the
conifer and cone specimens in lab. Where is the pollen produced? Where are the seeds
produced? Observe the Pine poster in the lab. Draw and label a conifer and cone.
There are also other groups of plants that are gymnosperms. Cycads are a group of
gymnosperms that was much more common during the time of the dinosaurs. Observe the cycad
specimens in lab. What type of plant do their leaves resemble? Where are the seeds produced?
Draw a cycad.
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Ginkgos are also gymnosperms. They are sometimes called living fossils because they were
known from fossils before a living tree was found. Observe the ginkgo specimen in lab. Note
the unusual fan-shape of the ginkgo leaves. Where are the seeds produced? Draw a ginkgo.
Another group of gymnosperms is the gnetophytes, which includes Gnetum and Ephedra (which
ephedrine comes from). These may be the group of plants that gave rise to angiosperms.
Observe the specimens in lab (if available).
Angiosperms
Angiosperms are plants that have evolved flowers and fruits. “Angiosperm” literally means
“covered seed, ” meaning the seeds are borne insides fruits. Flowering plants are the dominant
plants on earth today. The flower and fruit structure, by taking advantage of insects and animals,
allowed more efficient reproduction and dispersal, helping angiosperms to take over many
environments. Angiosperms also provide many of the foods we eat and fibers for making
clothes. There are two types of angiosperms: monocots and dicots. Their differences are shown
in the Table 1.
Table. 1. Comparison of Monocots and Dicots.
Cotyledons in germinating embryo
Root system
Veins of stem
Veins of leaves
Flower parts
Monocots
1
fibrous
scattered
parallel
3’s
Dicots
2
taproot
ring
netted
4’s or 5’s
Observe the slides of monocot and dicot stems. Also observe the Stems poster in the lab. Draw
and label the differences in the arrangement of vascular tissue (veins) in monocot and dicot
stems.
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Leaves can either be simple (undivided) or compound (divided into leaflets). Compound leaves
can be pinnate or palmate (see diagrams). Observe different types of leaves in the lab. Are
they monocots or dicots (veins parallel or netted)? Draw a label several leaves.
The structure of a flower consists of several parts arranged in 4 whorls. The lowest whorl is the
sepals. These are generally green and leaf-like, but not always. The next whorl is the petals.
These are usually colored and attract insects for pollination. The next whorl is the stamens,
which produce the pollen. The last whorl in the center of the flower is the carpel. The base of
the carpel contains the ovules, which produce the egg cells. At the top of the carpel is the
stigma, where the pollen lands to pollinate the flower. The pollen then grows down through the
carpel to the ovule, and releases the sperm to fertilize the egg.
Observe several flowers in the lab. Slice them longitudinally with a razor blade to see all the
parts. Are they monocots or dicots (flower parts in 3’s or 4’s and 5’s)? Draw and label a
monocot and a dicot flower.
Observe slides of stamen and carpels. Can you see pollen grains? Can you find ovules? Also
observe the Lily poster in the lab. Draw and label these structures.
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Fruits are designed for dispersal of the seeds. Some fruits blow in the wind, some are eaten by
animals, some are carried on animal fur, some float in water, some require fire in order to
germinate. Observe a variety of fruits in the lab. Draw a few and label the type of dispersal.
Fungi
Fungi are heterotrophic organisms. They do not photosynthesize. The body of the fungus is
called the mycelium. The mycelium is made up of individual fungal filaments called hyphae.
The hyphae secrete digestive enzymes into their food source, and then absorb the nutrients.
Fungi are important decomposers of dead and waste material in the environment. You looked at
bread mold in Lab 3. Review your drawings and notes about bread mold.
A mushroom is a reproductive structure of a fungus that produces spores. Observe the
specimens in lab. Where are the spores produced? Sketch a few examples.
Observe a slide of a Coprinus mushroom. Can you find spores? Draw and label this structure.
Lichens are a symbiotic association between fungi and green algae. There are three types of
lichens: fruticose, crustose, and thallose. Observe the specimens in lab and sketch a few.
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Lab 13: Animal Taxonomy
Introduction
The goal of being able to generalize about various organisms is facilitated by grouping related
species together, so that one can speak of “mammals,” “vertebrates,” “animals,” or other such
groups. The branch of systematic that deals with assigning species to these groups is called
taxonomy. Whenever a scientist first describes a new species, he or she suggests its relationship
to other organisms by assigning the species to taxa (plural of taxon). These taxa must be
specified in at least seven categories. These categories are kingdom, phylum, class, order,
family, genus, species. In the 18th century, Carolus Linnaeus simplified the lives of biologists
considerably by assigning to each species a name consisting of only two words. We still use his
binomial system. The first word is the name of the genus, which should be capitalized, and the
second word is the species, which should not be capitalized. The names must be either Latin or
latinized, should be written in italics or underlined. For example, the scientific name of
honeybees is Apis meliffera (bee that brings honey), and for humans the scientific name is Homo
sapiens (wise man). There are approximately one million species of animals on earth that have
been given a name, with an estimated 25 to 30 million still unclassified or undiscovered. Most
of the animals (discovered and undiscovered) are in the phylum Arthropoda and most of those
are in the class Insecta and most of the insects are in the order Coleoptera (beetles). When British
scientist J.B.S. Haldane was asked what would be inferred about the “Creator” from a study of
His works, he is reported to have replied "He has an inordinate fondness for beetles."
In today’s lab we will be studying different members of the Kingdom animalia. There are 32
phyla of animals each having slightly different characteristics. This lab will have pictures and
specimens representing nine phyla: Porifera, Cnidaria, Platyhelminthes, Nematoda, Mollusca,
Annelida, Arthropoda, Echinodermata, and Chordata. Make careful drawings and notes during
this lab. There will be a lab practical quiz next week!
Draw a representative of each phylum and list some descriptive characteristics.
Porifera
Cnidaria
Platyhelminthes
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Nematoda
Mollusca
Annelida
Arthropoda
Echinodermata
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Chordata
Within the phylum Chordata is the subphylum Vertebrata. Within the Vertebrata there are
several classes. Give an example and some characteristics of the following classes:
Chondrichthyes
Osteichthyes
Amphibia
Reptilia
Aves
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Mammalia
There are approximately 4,000 named species of mammals on the earth. Taxonomists generally
divide them between three groups: the egg-laying mammals or monotremes (order
Monotremata), the pouched mammals or marsupials (order Marsupialia), and the placental
mammals or eutherians, for which there are 18 orders. List an animal (including scientific name,
if given) in the following orders:
Monotremata
Marsupilia
Insectivora
Chiroptera
Carnivora
Pinnipedia
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Perissodactyla
Artiodactyla
Proboscidea
Cetacea
Edentata
Lagomorpha
Rodentia
Primates
There are two main groups of primates: the Prosimians and the Anthropoids. List some animals
in each of these groups.
Prosimians
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Anthropoids
List at least 4 orders of mammals that are found in and around the Hawaiian islands.
What are the only 2 mammals that are native to the Hawaiian Islands?
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Lab 14: The Honolulu Zoo
NOTE: You will visit the Honolulu Zoo on your own to complete this lab.
History of the Honolulu Zoo
(taken from their web site: http://www.honoluluzoo.org/history.htm)
Over 750,000 people visit the Honolulu Zoo annually. It is the largest zoo within a radius of
2,300 miles and unique in that it is the only zoo in the United States originating from a King's
grant of royal lands to the people. King David Kalakaua, Monarch of Hawai`i from 1874 to
1891, made lands of the Leahi Land Holdings available in 1876 to the people for a thirty-year
lease. That year, a "Kapiolani Park Association" of two hundred subscriber members assumed
the administration of the three hundred-acre park. The marshy parcel was a muddle of fishponds,
lagoons and islands where King Kalakaua maintained his collection of exotic birds. In 1877 the
area was named after the King's wife and opened as Queen Kapiolani Park.
Park Association members supported the unpromising park with the help of royal grants through
1894. In those days, the park's primary attractions were the exotic bird collection and horse
racing, especially the running of the Rosita Cup, held annually on King Kamehameha Day.
Peacocks, trees, and palms were added to the park, with plantings obtained from Golden Gate
Park in San Francisco. Roads and trolley lines were extended to include "Waikiki Road at
Makee", today's intersection of Kalakaua and Kapahulu Avenues. The park was permanently
established in 1896 and the City and County of Honolulu assumed administration of city parks in
1914. Today, the zoo continues under the administration of the City, but as a part of the
Auditoriums Department. During 1914 to 1916, the young administrator of Parks and
Recreation, Ben Hollinger began collecting animals for exhibit at Kapiolani Park. The first
animals included a monkey, a honey bear and some lion cubs. In 1916 Daisy, a friendly African
elephant arrived in Honolulu on the Niagra, a steamship on it's way from Australia to Canada
transporting animals for mainland zoos and circuses. Ben Hollinger persuaded city merchants to
purchase Daisy and for years she delighted Honolulu children. Many recall riding as a youngster
around the park on her back.
Daisy's career ended tragically in 1933, when for unexplained reasons, she attacked and trampled
to death her keeper George Conradt. She was put down by police marksmen and buried at sea.
Pictured right are Daisy and her keeper George Conradt. During the depression years, the Zoo
faltered and nearly closed. The grounds and facilities fell into disrepair. In 1974, the donation of
a camel, elephant, chimpanzees and deer by the Dairymen's Association sparked a renewal for
the Honolulu Zoo. During this time the City took important steps to set the course for today's
Zoo. It approved a Master Plan that determined the boundaries of the present 42-acre site at the
north end of Kapiolani Park. It hired its first full-time director, Paul Breese, and a staff of
thirteen. The animal collection, increased by purchase, trade and donations, was housed in newly
constructed facilities, some of which still provide foundations for newer exhibits. In 1952 the
Zoo's design was revised, and again modified to take on the shape and form seen in the "old zoo"
exhibits like the small mammal row along Kapahulu Avenue.
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Address:
The Honolulu Zoo
151 Kapahulu Avenue
Honolulu, HI 96815
808-971-7171
Zoo Hours: 9:00 am to 4:30 pm daily
As you tour the zoo, find a representation for each of the following mammalian orders and
provide a brief description of the behaviors you observe the animal performing. Describe a
physical adaptation unique to each animal. Describe what type of habitat each animal would
naturally live in. How is that represented in the exhibit? Try to find the scientific name of the
animal (e.g. Procyon lotor for raccoon).
Order
Carnivora
Proboscidea (elephants)
Primates
Perissodactyla (odd-toed hooved animals; horses, zebras, and rhinos)
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Artiodactyla (even-toed hooved animals: pig, deer, cow)
Which species of mammal did you see in greatest abundance at the zoo?
What were the largest and smallest reptiles that you observed?
Describe the most colorful and the dullest birds you observed?
What might be the adaptive value of these colors?
Ethogram and scan sampling experiment:
Pick one mammal group and observe their behavior for 15 minutes. From your observations,
create an ethogram with five of their most characteristic behaviors, such as: walking, resting,
playing, etc. Write a brief description of what constitutes each behavior.
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Ethogram:
Behavior 1:
Behavior 2:
Behavior 3:
Behavior 4:
Behavior 5:
Pick a single member of the group and observe its behavior for an additional 15 minutes using
the scan-sampling technique. Scan-sampling is a systematic and quantifiable means of creating
a general record of animal behavior. Every 30 seconds record which of the 5 behaviors the
animal is performing at that moment (for that 1-second period). This will give you a total of 30
observations (2 per minute, one every 30 seconds) in 15 minutes. Create a graph of the recorded
behaviors with the Y-axis being number of observations and the X-axis the five behaviors. Use
the table on the next page to record the animal’s behavior -- put a different behavior on the top
row at the head of columns 1-5.
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Time
0
.30
1.00
1.30
2.00
2.30
3.00
3.30
4.00
4.30
5.00
5.30
6.00
6.30
7.00
7.30
8.00
8.30
9.00
9.30
10.00
10.30
11.00
11.30
12.00
12.30
13.00
13.30
14.00
14.30
15.00
Total
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4
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Graph the total number of observed behaviors in 15 minutes (use a bar graph).
What conclusions can you make from your graph?
What might be the adaptive importance of these behaviors?
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What types of animals would you not expect to see this behavior pattern? Why?
What type of animal would you expect to see similar behavior patterns? Why?
Discussion:
What do you believe are the advantages and disadvantages of zoos to the public, the individual
animals, and to the animal species in general? What did you enjoy most of your visit.
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Lab 15: Population Ecology –
Population Density and Survivorship Curves
Introduction
The word ecology is derived from the Greek oikos, which means “house.” Broadly defined,
ecology, is the study of interactions between living organisms and the environment. Individuals,
whether they are bacteria or humans, do not exist in a vacuum. Rather they interact with one
another in complex ways. As such, ecology is an extremely diverse and complex study. Let’s
look at the levels of organization in ecology.
A population is a group of organisms of the same species occupying a given area at a given
time. For example, you and your fellow students in the lab at the moment are a population; you
all are Homo sapiens in biology call right now. The place you are occupying, your lab room, is
your habitat. Of course, you are sharing your habitat with other organisms; bacteria, insects,
fungi, plants are all possibly present in your lab room. If so, there are other populations in your
habitat.
A community consists of all those population of all species occupying a given area at a given
time. Our lab community consists of humans, bacteria, insects and plants.
Our community exists in a physical and chemical environment. This combination of the
community and its environment comprise an ecosystem. Our lab ecosystem consists of humans,
bacteria, insects, plants, air, lab benches, walls, floors, light, heat, and so on.
Population Density
Characteristics of a population include size, density, growth rate, dispersion, and survivorship.
Rarely is every individual in a population counted to determine the exact number of individuals
in the area. This would be very tedious and time consuming (although the U.S. government
attempts to do it every 10 years). More often, population size and density is estimated. In the
sample plot method, a small area of the population is sampled and the number of individuals is
extrapolated to the whole area. In the mark-recapture method, individuals are trapped, marked
released, and then trapped again at a later time. The proportion of marked individuals recaptured
the second time is used to estimate population size and density. In this exercise, we will estimate
the density of a population of beans living in a paper bag.
Procedure:
Students should work in groups of 4. A group report is acceptable for grading purpose.
Sample Plot Method
1. You want to determine the population density of pine trees in the forest below. Draw several
2cm x 2cm sample plots. These will represent 1 hectare plots that would be used in actual field
experiments. Try to scatter the plots randomly. The more plots you use, the better the
population estimate will be, however, you don’t want to use so many plots that it will be too
much work to count.
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2. Now count the number of individual pine trees in all the sample plots. Add up the area of all
your sample plots together (use 1 hectare as the area of each sample plot). Then calculate
population density with the formula below:
Population density = # individuals in all sample plots
area of all sample plots
3. If the total area of the entire forest is 80 hectares, estimate population size with the formula
below:
Population size = population density X total area
Mark-recapture Method
1.
2.
3.
4.
5.
6.
Obtain a paper bag containing beans. Randomly draw out 40 beans.
Make a mark on each bean with a pencil or marker.
Return the marked beans to the bag.
Shake the bag to thoroughly mix the beans.
Draw out another 40 beans.
Use the formula below to estimate the size of the population.
N (population size) = (# marked individuals) (total # caught second time)
(# recaptured marked individuals)
Survivorship Curves
Within a population, some individuals die very young, while others live to old age. To a large
extent, the pattern of survivorship is species-dependent. Generally, three patterns of survivorship
have been identified. These are summarized as the survivorship curves, graphs that indicate the
pattern of mortality (death) in a population (Figure 1). Humans in highly developed countries
with good health-care services are characterized by a Type I curve, in which there is high
survivorship until some age, then high mortality. The life insurance industry uses this
information to determine risk groups and set premiums. In this exercise, we will study
populations of dice, using them as models of real populations to construct survivorship curves.
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Figure 1. Survivorship Curves
Procedure
Students should work in groups of 4.
Population 1.
1. Empty a bucket of 50 dice onto the table or floor.
2. Assume that all individuals that come up as 1’s die of heart disease. All others survive.
3. Pick up all the 1’s, set them aside (in the cemetery) and count all the individuals who have
survived. Record the number of survivors in this generation (Generation 1) in Table 1.
4. Return the survivors to the bucket.
5. Dump the survivors onto the table again and remove the dead (1’s) that occurred during this
second generation.
6. Count and record the number of survivors.
7. Continue this process until all the dice have died from heart disease.
Population 2.
1. Start again with a full bucket of 50 dice. Assume that the 1’s die of heart disease and the 2’s
die of cancer. Proceed as described for Population 1, recording the number of survivors, until
all dice are dead.
2. Now determine the percentage of survivors for each generation for both populations with the
following formula:
percentage surviving = number surviving x 100
50
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Plotting Survivorship Curves
On the log paper provided, make a logarithmic plot of the percentage surviving in each
population. Note that on the log paper, the horizontal lines become closer together toward the
tope of the page. The scale of the vertical axis runs from 1 at the bottom to 9 near the middle,
then from 1 to 9 again near the top and then 1 again at the very top. The 1 at the very top
represents 100%, the 9 below it 90% and so on. The 1 in the middle is 10%, the 9 below it 9%,
and so on. The 1 at the very bottom is 1%.
Compare your graph with Figure 1. What type of survivorship curve did you find for the dice
populations?
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Lab 16: Community and Ecosystem Ecology –
Foraging Strategy, Food Webs, and Energy Flow
Introduction
In this laboratory you will investigate some of the factors that determine and animal’s foraging
strategy. There are many tradeoffs involved in and animal’s choice of food. For instance, is it
more advantageous to eat small prey, which may not have a lot of nutritional value but are easy
to catch or to search for more nutritious prey? You will also investigate predator-prey
relationships by looking at changes in predator and prey populations.
To accomplish this you will use simulations, or models, of natural systems. Scientists often use
models to simplify complex systems. Rather than try to control all possible variables in a field
experiment it is sometimes useful to set up a model in which you can define and control the
components. Such simple models are often instructive.
Foraging Strategy
Students should work in groups of 4. Group reports are appropriate for grading purpose.
General Rules for the Model:
1. The model habitat is a container of sand.
2. The prey (food resource) is beans.
3. You will be the foraging animal (predator).
4. Use only chopsticks to forage for the beans.
5. Do not remove any sand from the container.
6. Each member of your team takes a turn as a forager (10 seconds allowed).
7. Each prey item must be placed in a cup (prey handling time).
8. One person should act as the timer/recorder and verify that each forager follows the rules.
The person who has just finished foraging will become the recorder for the next forager.
9. At the end of each turn, the recorder must smooth out the sand and cover any exposed beans.
Single Prey Item
1. Mix 30 kidney beans (reddish-brown) into the sand, making sure all are covered.
2. Take turns foraging as described above. Each predator must capture 3 beans within 10
seconds to survive.
3. Stop at 3 beans or 10 seconds whichever happens first.
In the table on the following page, record the number of prey remaining after each turn and the
time required to catch 3 beans.
Continue until all predators have starved to death.
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Forager
Time to catch 3 beans
Number of beans remaining
(started with 30)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
How many turns did it take before all predators died?
What factor is indicative of foraging success? (When was foraging most successful?)
How was foraging affected as food became depleted?
Give a real-world example of the type of situation you just modeled
Were any beans left when all the foragers died?
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How could you change your simulation to increase the forager’s success?
How could you change your simulation to increase prey survival?
Multiple-prey system:
In this part you will simulate a system in which a predator feeds on more than one species of
prey, differing in nutritional value and ease of capture: Kidney beans, lima beans, and northern
beans
The procedure is essentially the same as for the single prey item except that in order to survive, a
predator must capture one of the following combinations of beans:
1.
2.
3.
4.
5.
4 northern (brown)
3 kidney
2 lima (white)
3 northern and 1 kidney
3 northern and 1 lima
Remove all the beans from the previous foraging. Then start with 40 northern beans, 30 kidney
beans, 20 lima beans (* make sure that you have removed all the beans from the first exercise).
Again use only chopsticks, but this time give each subject 15 seconds to capture their diet.
In the table on the following page, record the number of prey remaining and the number of
seconds required for each turn.
Continue until all predators have starved to death.
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forager
time to
catch
number of northern
remaining
40
number of kidney
remaining
30
number of lima
remaining
20
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
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Make a graph of the how the number of different beans changed over the experiment, with the
number of beans remaining on the Y-axis and the foraging turns on the X-axis. (There should be
three plotted lines, one for each type of bean.)
How many turns did it take before all predators died?
Which prey species was depleted first? Why do you think this might be so?
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Competitive Exclusion Principle
In this section you will look at a multi-prey and multi-predator situation. The model is designed
to demonstrate differential survival of different types of predators who are competing for the
same prey. The predator who is best adapted will have greater reproductive success. Predators
that are not as well adapted will be excluded, or die out. This is known as competitive exclusion
1. Set up your sand with 40 northern, 30 kidney, and 20 lima beans.
2. Each team in class will be assigned to a predator type. Each type will have a structural
adaptation that affects its ability to capture prey: chopsticks, forks, spoons, knives, etc. Upon
capture, each prey item must be place into a cup held in the predator’s other hand.
3. Two members from each team will participate in the first round of foraging, which will last
for 20 seconds. You are not allowed to push or scrape prey into your cup. You are allowed
to steal prey being pursued by another predator, but only if it increases your capture rate.
Prey will be deducted if your cup has excess sand.
4. At the end of the round, each team will count their prey.
5. Results will be tallied on the board. The predator group with the most prey will gain a
member (successful reproduction), and each of the other predator groups, with fewer prey,
will lose one member.
6. The remaining prey will be doubled before the next round of foraging.
7. Repeat this process for 5 generations. Your instructor will keep track of changes on the
board.
Make a graph the number of each type of predator vs. generations. (There should be 4 lines on
one graph.)
Briefly summarize and comment on your results.
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Ecosystems
An ecosystem consists of the living community plus the non-living environment. Each
population of the community plays a different role within the structure of the community. Each
community consists of producers, consumers, and decomposers.
Food Webs
Producers are autotrophic organisms, such as most plants and a few microorganisms. They
utilize the energy of the sun or chemical energy to produce organic compounds from inorganic
compounds.
Consumers are heterotrophic organisms. In ecological studies, consumers are usually classified
into trophic (feeding) levels by what they eat.
• Primary consumers are herbivores, animals that eat plants material.
• Secondary consumers are organisms that eat primary consumers. These organisms are
carnivores. (Parasites may be considered primary or secondary consumers depending on
whether they are feeding on a producer or another consumer.)
• There may also be tertiary consumers that eat the secondary consumers, or quaternary
consumers that eat the tertiary consumers.
• Decomposers include bacteria, fungi, and some protists that break done organic material
into smaller molecules, which are then recycles into the ecosystem. These are also called
detritivores, because they eat detritus, or dead, waste material.
• Omnivores may cross trophic levels and eat either producers or consumers.
How would you classify yourself with respect to your feeding strategy?
Below is a list or organisms in a forest community and their sources of energy. Indicate the most
specific trophic level for each.
Human (raspberries, hickory nuts, deer, rabbits)
Raspberry (sun)
Deer (plants)
Bear (raspberries, deer)
Coyote (deer, rabbits)
Nematode (living hickory tree roots)
Bacteria species 1 (raspberry)
Bacteria species 2 (deer)
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Bacteria species 3 (dead trees, raspberry, bears, and deer)
Weasels (young rabbits)
Mosquito (blood of living humans, deer, and rabbits)
Hickory tree (sun)
Fungus species 1 (living raspberry)
Fungus species 2 (dead trees and raspberry)
Rabbit (raspberries)
Now construct a food web by placing the names of the organisms at their appropriated trophic
levels. Then connect arrows to the organisms to complete the food web.
Trophic Level
Organisms
Decomposers
Omnivores
Secondary consumers
Primary consumers
Producers
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Energy Flow Through and Ecosystem
Ecologists have learned through careful measurement that the amount of energy captured
decrease at each succeeding trophic level. Of the total amount of the energy of the sun falling on
a green plant, the plant is capable of capturing only about 1% of the energy. That is to say, only
a small fraction of the light energy striking the surface of a leaf is converted to ATP to make
sugars. A primary consumer may only be able to capture about 10% of the energy stored in a
plant. A secondary consumer may only capture 10% on the energy stored in the body of the
animal it eats.
How much of the solar energy that was captured by plants has been captured by the secondary
carnivore that feeds on an herbivore?
Suppose a tertiary consumer eats the secondary consumer. Assuming a similar flow of energy
(10%), how much of the sun’s original energy does the tertiary consumer gain?
Suppose an omnivore can obtain all the nutritional requirements necessary for life by eating
either plant or animal material. From an energetics standpoint, by which route will the greater
amount of the sun’s energy be captured?
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Lab 17: Human Health and Physiology
Introduction
Today more Americans than ever are concerned about health. Proper nutrition, adequate
exercise and sleep, and managing stress are all viewed as fundamental to maintaining a
healthy lifestyle. Though human health and physiology are not a separate part of the
Biology 101 lecture curriculum, most students find the workings of their own bodies an
interesting subject. For this reason we have included a special laboratory on the
mechanisms, capabilities, and limitations of the human body, with an emphasis on issues
pertaining to good health.
The Respiratory System
The respiratory system is the system responsible for supplying oxygen to the body and removing
gaseous wastes. The capacity to do this is a function of the amount of air that the lungs can hold.
Air in the lungs is divided into four mutually exclusive volumes: tidal volume (TV), inspiratory
reserve volume (IRV), expiratory reserve volume (ERV), and residual volume (RV).
Tidal volume (TV) is the volume of air inhaled or exhaled during breathing. It normally varies
from a minimum at rest to a maximum during strenuous exercise.
Inspiratory reserve volume (IRV) is the volume of air you can voluntarily inhale after
inhalation of the tidal volume.
Expiratory reserve volume (ERV) is the volume of air you can voluntarily exhale after an
exhalation of the tidal volume.
Residual volume (RV) is the volume of air that cannot be exhaled from the lungs. That is,
normal lungs are always partially inflated.
All the lung volumes except residual volume can be measured or calculated from measurements
obtained by using a spirometer. The simple principle behind a wet spirometer is the
displacement of a volume of water by a volume of air exhaled from the lungs; the mechanism is
connected to a gauge which measures the air volume.
Procedure:
Students should work in groups of 4.
1. Place a new mouthpiece on the spirometer. Holding your nose, sit quietly and breathe
normally. After you feel comfortable, start counting as you inhale. After the fourth inhalation,
exhale normally into the spirometer. Read the volume indicated by the gauge. Record the volume
in Table 1 below (TV, trial 1). Reset the spirometer. Repeat this procedure two more times (trials
2 and 3). Calculate the average tidal volume at rest.
2. As before, hold your nose, sit quietly and breathe normally. After you feel comfortable, start
counting as you inhale. After the fourth inhalation, exhale a normal, quiet breath into the room.
Now, exhale as much of the remaining air in the lungs as possible into the spirometer. This
value is the expiratory reserve volume (ERV). Record the volume in Table 1 (ERV, trial 1).
Reset the spirometer and repeat this procedure two more times (trials 2 and 3). Calculate the
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average ERV at rest.
3. We will not directly measure inspiratory reserve volume (IRV) in this laboratory, as
this would require inhaling from the spirometer and is potentially an unsanitary
procedure. Instead, we will measure another indicator of lung capacity called vital
capacity (VC), and then calculate IRV:
Vital capacity (VC) = TV + ERV + IRV
To determine vital capacity, inhale as large a quantity of air as possible. Exhale into the
spirometer to the fullest extent. Try to completely empty the lungs. The exhalation should be
done in a smooth, steady manner. The figure obtained is the vital capacity (VC). Record in Table
1, and repeat this measurement two more times, resting between measurements. Compute the
average VC.
4. Using the average values for TV, ERV, and VC, compute inspiratory reserve volume (IRV).
Table 1. Measured values for TV, ERV, and VC, with calculations for IRV
Trial #1
Trial #2
Trial #3
Average
TV (Tidal Volume)
ERV (Expiratory Reserve
Volume)
VC (Vital Capacity)
IRV = VC - TV - ERV
5. Record your height in inches: _____________. Now, write your vital capacity, height, and
whether or not you smoke on the board; your name is not necessary.
Calculate what percentage of total lung capacity you utilize in a normal breath.
Graph the vital capacity vs. the height of each of the students. Is there a relationship between
vital capacity and height? If so, describe it in words. Circle all the points of people who smoke.
Is there a relationship between vital capacity and smoking?
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The Circulatory System
The human circulatory system contains approximately 5 liters of blood. Human blood is about
45% cells by volume, although it is only slightly thicker than water. Most of the cells are red
blood cells, which contain the oxygen-carrying pigment hemoglobin. Blood cells are suspended
in a fluid called plasma, which constitutes about 55% of the blood by volume. Plasma is mostly
water but contains many dissolved substances, including gases, nutrients, wastes, ions,
hormones, enzymes, antibodies, and other proteins.
The flow rate of blood within the circulatory system is adjusted to meet the demands placed upon
it by the body. In this exercise, you will look at the effects of various physiological factors upon
blood flow as measured by pulse rate and blood pressure.
Blood pressure is the force your heart uses to push blood through the blood vessels
(arteries and veins). The heart is like a pump. When it contracts, it forces blood through
the blood vessels, and pressure increases. This is called systolic pressure. When the heart
relaxes between beats, the pressure decreases. This is called diastolic pressure. Normal
blood pressure values are 110 to 130 mm Hg systolic and 70 to 90 mm Hg diastolic. (The
numbers are in millimeters of mercury, a standard measure of pressure also used in
barometers.) The systolic pressure is always recorded first, and the diastolic pressure is
second. For example, a resting blood pressure reading for an adult may be 120/80.
Blood pressure can fluctuate throughout the day due to physical activity, medications you may
be taking, your emotional state, or other physical or psychological factors. A single
measurement, therefore, doesn’t tell the whole story. You need several readings to get an
accurate indication of your blood pressure. When blood pressure is consistently above normal,
however, it is called hypertension (high blood pressure). Hypertension is sometimes the result
of the inner walls of the arteries accumulating fats, as they do in the condition called
arteriosclerosis. If this occurs, the blood pressure is elevated because the diameters of the
passageways are narrowed, and the same volume of blood being forced through a smaller
diameter opening will exert more pressure on the walls of the blood vessels.
Blood pressure is measured using an inflatable cuff with a pressure device called a
sphygmomanometer, and a stethoscope. The cuff is placed around the upper arm and the
stethoscope positioned over the artery just below the cuff. The cuff is inflated until its pressure
closes off the main artery in the arm and blood ceases to flow. No pulse, therefore, can be
detected below the cuff. Then the pressure is gradually released. When the pulse is first audible
in the artery, this means that the pressure pulses created by the contracting left ventricle of the
heart are just overcoming the pressure in the cuff and blood is flowing. This is the first of the two
readings, the systolic pressure. Cuff pressure is then further reduced until no pulse is audible.
An inaudible pulse at this point indicates that the artery is no longer constricted and blood is
flowing continuously through the artery; the pressure between ventricular contractions is just
overcoming the cuff pressure. This is the second of the two readings, the diastolic pressure.
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Procedure:
I. Resting Pulse Rate
The easiest area to locate the pulse is at the artery in the wrist just below the thumb. Locate this
pulse by placing your middle and index fingers (not the thumb) on the wrist and gently pressing
down until you can feel the pulse. Count the pulses for 15 seconds and then multiply by 4 to get
the number of beats in one minute (60 seconds). Record this in Table 2. Repeat this
measurement, and compute the average pulse rate.
Table 2. Pulse rate and blood pressure.
Pulse #1
Pulse #2
Average
Blood
Pressure #1
Blood
Pressure #2
Average
II. Resting Blood Pressure
1. Have the subject seated comfortably with the forearm on a smooth surface at heart level. The
needle of the sphygmomanometer should be at zero with the cuff deflated and the exhaust valve
open.
2. Locate the artery on the inside of the upper arm just above the elbow. The deflated cuff should
be wrapped snugly (but not tightly) around the upper arm 2 to 3 cm above the bend in the elbow.
Be sure to center the inflatable bag over the artery.
3. While feeling the pulse with one hand, close the exhaust valve and rapidly inflate the cuff with
the other hand. Inflate to a pressure of about 30 mm Hg above the point where the pulse ceases
(usually @ 180 mm Hg).
4. Place the stethoscope over the artery just below the cuff. Exhaust the cuff at a rate of
2 to 5 mm Hg per second. As the cuff exhausts, listen for the first clear tapping sound. The
sphygmomanometer reading at this point is the systolic pressure, the pressure in the blood
vessels when the heart is contracting, forcing blood into the arteries.
5. Continue deflating the cuff. When the sound becomes distinctly muffled and softer, record the
reading. This is the diastolic pressure, the pressure in the blood vessels as the chambers of the
heart are filling.
6. Repeat this process and calculate an average, recording your results in Table 2. Be sure to rest
for a couple of minutes between readings to let your blood vessels recover from the pressure of
the cuffs.
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III. Effects of Aerobic Exercise on Blood Pressure
1. Choose one member of your group to examine the effects of vigorous exercise on resting
blood pressure. Have the subject run up and down a flight of stairs three times without stopping.
2. Immediately have the subject sit down. Measure pulse rate and blood pressure. Record your
results in Table 3 (0 minutes after exercise).
3. Repeat measurements of pulse rate and blood pressure at 2-minute intervals until values are
back to normal, resting levels.
Table 3. Recovery of resting blood pressure after aerobic exercise.
Minutes after 0
exercise
Pulse rate
(beats/min)
Blood pressure
(mmHg)
2
4
6
8
10
12
14
IV. Effect of Stimulants (Caffeine) on Blood Pressure
1. Choose a subject who has not drunk coffee or soft drinks for the past three hours.
2. Determine resting pulse rate and blood pressure.
3. Have the subject drink 6-8 oz. of coffee or soda at a moderately fast pace.
4. Take pulse rate and blood pressure readings immediately on completion and at 2-minute
intervals thereafter for 15 minutes. NOTE: It is important that the subject remain quietly seated
during the test so that other variables do not influence the measurements.
5. Record your observations in Table 4.
Table 4. Recovery of normal pulse rate and blood pressure after consumption of caffeine.
Minutes after
0
drinking
Pulse rate
(beats/min)
Blood pressure
(mmHg)
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4
6
8
10
12
14
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6. Graph the results of the aerobic exercise and caffeine. One graph should represent change in
heart rate and the other a change in blood pressure. The graph representing blood pressure should
have two plotted points every 2 minutes: systolic and diastolic pressure. Be sure to indicate
labels for each axis, and a title for the graph.
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