Introduction to
Biology
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Biology – The Study of Life
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Life arose more
than 3.5 billion
years ago
First organisms
(living things) were
single celled
Only life on Earth
for millions of
years
Organisms changed
over time (evolved)
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New organisms
arose from older
kinds
Today there are
millions of species
They inhabit
almost every
region of Earth
today
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Themes of Biology
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Cell structure and
function
Stability and homeostasis
Reproduction and
inheritance
Evolution
Interdependence of
organisms
Matter, energy, and
organization
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Scientific Method
Chapter 1.3
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Observation – STEP 1
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Employing your five senses to
perceive objects or events
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Asking a Question
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Based on observations; one or more
questions are generated
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Forming a Hypothesis – STEP 2
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A statement is testable if evidence can be
collected that either does or doesn’t
support it
It can never be proven beyond doubt
Often must be refined and revised or
discarded
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The Hypothesis --
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Is a statement made in advance
that states the results that will
be obtained from testing the
hypothesis
Often written in the form of an
“if-then” statement
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Experimenting – STEP 3
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Testing a hypothesis or prediction by
gathering data under controlled conditions
– conducting a controlled experiment
 Based on a comparison of a control
group with an experimental group
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Both groups are identical except for
one factor (independent variable)
Observations and measurements are
taken for a particular factor
(dependent variable) in both groups
 Driven by or results from independent
variable
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Measuring
 Involves quantitative data that can
be measured in numbers &/or
qualitative data information that
isn’t numbers
Sampling
 Technique of using a sample – a
small part – to represent the
entire population
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Organizing Data – STEP 4
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Involves placing observations and
measurement (data) in order
 Graphs, charts, tables, or maps
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Analyzing Data – STEP 4 cont)
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Collected and organized data must be
analyzed
 Process of determining whether data
are reliable or whether they support or
do not support a hypothesis or
prediction
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Conclusion – STEP 5
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Conclusions are made on the
basis of facts, not observations
 Often drawn from data
gathered from a study or
experiment
 Should relate to the
hypothesis
 Should be re-testable
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Communication – STEP 6
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Scientists must share the results of
their studies with other scientists
(peers)
Publish findings in journals
Present their findings at scientific
meetings
Scientists must be unbiased
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Should not tamper with their data
Only publish & report tested & proven
ideas
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Communication
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Sharing of information is essential to
scientific process
Subject to examination and verification
by other scientists
Allows scientists to build on the work of
others
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6 Steps of the Scientific Method
1. Observation- noting or perceiving
objects or events by using the 5 senses
(causes a question to form)
2. Hypothesis- proposes an
explanation/educated guess based on
prior information (can be tested)
6 Steps of the Scientific Method
3. Prediction- If/then statement (If
the hypothesis is true, then this would
happen)
6 Steps of the Scientific Method
4. Experiment- test the hypothesis,
usually comparing results of an unknown
result to that of a known (numbered
steps for the procedure)
6 Steps of the Scientific Method
4. Experiment
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Control: a standard for comparison
Constant: a factor that doesn’t vary
in any part of the experiment
Independent Variable: manipulated
on purpose
Dependent Variable: the response
to the independent variable
6 Steps of the Scientific Method
5. Data- collected & analyzed as tables,
charts, graphs
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- is data reliable
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- does it support or reject
hypothesis
6 Steps of the Scientific Method
5. Data
 Quantitative data are expressed as
numbers, obtained by counting or
measuring.
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Qualitative data are descriptive and
involve characteristics that can’t
easily be measured.
6 Steps of the Scientific Method
6. Conclusion- report to others so
rejection, verification or modification
of the hypothesis occurs (peer review)
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- inferences: conclusion made on
facts & previous knowledge rather
than on direct observations (not
directly testable)
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Scientific investigations begin with
observation, the act of noticing and
describing events or processes in a careful,
orderly way.
For example, researchers observed that
marsh grass grows taller in some places than
others. This observation led to a question:
Why do marsh grasses grow to different
heights in different places?
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For example, researchers inferred that
something limits grass growth in some
places. Based on their knowledge of salt
marshes, they hypothesized that marsh
grass growth is limited by available
nitrogen.
The researchers added nitrogen
fertilizer (the independent variable) to
the experimental plots. They then
observed the growth of marsh grass
(the dependent variable) in both
experimental and control plots.
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Scientists record experimental
observations, gathering information
called data. There are two main types
of data: quantitative data and
qualitative data.
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Quantitative data are numbers
obtained by counting or measuring. In
the marsh grass experiment, it could
include the number of plants per plot,
plant sizes, and growth rates.
Qualitative data are descriptive and
involve characteristics that cannot usually
be counted. In the marsh grass
experiment, it might include notes about
foreign objects in the plots, or whether
the grass was growing upright or
sideways.