Natural Selection at Work
Brigitte Steinmetz
John Adams Middle School
Santa Monica – Malibu Unified
Charles Darwin
ƒ Famous Naturalist
– Did many things…
things…
ƒ Discovery of the
Galapagos Finches
during a 5 year
voyage on the H.M.S.
Beagle (1831(1831-1836).
1809 -1882
http://anthro.palomar.edu/evolve/evolve_2.htm - 8/24/2004
Darwin’s Observations
ƒ Identified 13 species
of finches on the
islands, but only one
on the mainland!
ƒ Each species had a
beak that differed
slightly from the other.
http://anthro.palomar.edu/evolve/evolve_2.htm - 8/24/2004
1
What do you think?
ƒ Make a hypothesis as to why you think the
Galapagos Finches had different types of
beaks?
http://anthro.palomar.edu/evolve/evolve_2.htm - 8/24/2004
Predator Prey Lab
Predator (5 morphs)
Prey (5 morphs)
Knife
Spoon
Fork
Forceps
Hand
Green
Black
Brown
Red
Green
Environment – Green grass next to Volleyball
courts.
Predator Prey Lab Rules
ƒ
ƒ
ƒ
ƒ
Utensil = mouth
Cup = stomach
40 seconds to feed per round
Grab food with utensil and place into cup.
NO SCOOPING!
ƒ GOOD SPORTSMANSHIP – no knocking
cups over or utensils!
ƒ No hunting after hours! Stop on teacher’
teacher’s
signal.
2
What do you think?
ƒ Which predator do you hypothesize
will be the most successful? Least
successful?
ƒ Which prey do you hypothesize will
be the most successful? Least
successful?
Let’s try to prove our hypothesis wrong!
Post Lab
Generation vs. # of Surving Predators
3.5
Students graph their
data.
3
# of Surviving Predators
2.5
Hand
2
Spoon
Forceps
Fork
1.5
Knife
1
0.5
Generation vs. # of Surviving Prey
0
450
Generation 1
Generation 2
Generation 3
Generation
400
350
# of Surviving Prey
300
White
250
Red
Brow n
Black
200
Green
150
100
50
Students answer
analysis/conclusion
questions.
0
Generation 1
Generation 2
Generation 3
Generation
Concepts
ƒ Individuals in a species are different in that
their characteristics will be varied from one
another; happens randomly via genetic
mutations.
ƒ Some characteristics help the individual
survive and reproduce (adaptation
(adaptation)) passing
on those traits to the next generation
(natural selection).
selection).
3
Tying Everything Together
ƒ In addition to beak differences, Darwin
noticed that the environment (food source)
for each bird was different.
ƒ His conclusion…
conclusion…mainland finches adapted
to new environment – those that had the
best beak for a particular environment
survived/reproduced making more offspring
with their characteristics. Those that didn’
didn’t
died!
We have NATURAL SELECTION!
Peppered Moth Example
Today –
Environmental
controls in
place (less
pollution);
Lichen
growing back;
abundance of
moths light in
color
increasing.
1895 –
98% of
moths
were dark.
Pre – Industrial
Revolution
Post – Industrial
Revolution
Lichen on trees.
No lichen (killed by soot)
on trees.
http://anthro.palomar.edu/evolve/evolve_2.htm - 8/24/2004
4
Predator Prey Lab Lesson Plan
Objectives: Students will be able to explain how natural selection leads to evolution.
CA State Standards:
Middle School Life Science Standards:
3a-b, 4f, 7c, 7e
High School Biology Standards:
7a-d
Materials:
Predators: 5 morphs (your choice) – some examples = fork, spoon, hand, forceps, knife
Prey: 5 morphs (your choice – some examples = different colored beans, different colored string
Mouths: cups (1 per student)
Stopwatch
Calculator (optional)
Plan:
-
-
-
This lab can be done in the classroom and outside of the classroom.
Divide the students into 5 equal groups.
Assign each group a particular predator.
Spread out the prey on the feeding ground (i.e. classroom floor, grassy area).
Explain the following rules to students:
o They will have 40 seconds to feed. Students must not begin early.
o They must grab the food using their utensil and place the food in the cup with the
utensil. No SCOOPING.
o They must show good sportsmanship. Knocking other students’ cups over or
utensils is grounds for disqualification.
o No hunting after hours. Students must stop on teacher signal.
Optional: Introduce a secondary predator during feeding time. These secondary predators
hunt the primary predators. Upon tagging individual they must empty contents of cup
(stomach) into secondary predator’s cup and leave the feeding ground.
When the feeding time is up, have students stop and count the number of each type of prey
they caught. They should write down these numbers on their data sheet.
Ask each student for their total prey caught for each type. Add all students’ totals together
for each type of prey. Fill in the data chart on the board.
Have the students help you calculate and fill in the chart on the board. Calculate the
following with the students help:
o Total prey killed by each predator
o Average kills per predator
o # of surviving predators
o total prey killed for each type
o number of surviving prey
o population of next prey generation
Brigitte Steinmetz (John Adams Middle School, Santa Monica – Malibu Unified School District)
Page 1
8/15/2004
-
-
-
Determine the next generation of predators based on the number of students who went
extinct. The successful predators will reproduce and their offspring will be the students who
became extinct in the first round. For example, if 8 students became extinct then you will
want to assign these 8 students a new type of predator (the offspring).
Repeat the above steps for a total of 3-4 rounds.
Back in the classroom, graph the results. You could graph the following:
o Predators: Generation (x-axis) vs. # of individuals (y-axis)
o Prey: Generation (x-axis) vs. # of individuals (y-axis)
o Predators: Type of predator (x-axis) vs. Total # of prey killed (y-axis)
o Prey: Type of prey (x-axis) vs. Total # of prey survived (y-axis)
Ask students to analyze the graph. Possible questions:
o Which type of predator was the most successful? Why?
o Which type of prey had the best survival rate? Why?
o What factors do you think could change the outcome of this experiment?
o What characteristics made it difficult for predators to feed? Easy?
o What characteristics made it easy for prey to survive? Difficult?
References/Resources:
Internet:
http://www.csun.edu/science/ - Loads of information and links to several other sites.
http://www.pbs.org/wgbh/evolution/ - PBS website
http://www.bbc.co.uk/education/darwin/index.shtml - BBC education
http://anthro.palomar.edu/evolve/evolve_2.htm
http://anthro.palomar.edu/synthetic/synth_7.htm
http://www.mc.maricopa.edu/~reffland/anthropology/origins/asm97.html
Books:
Prentice Hall Life Science Text Book, Prentice Hall Inc., New Jersey, 2001.
Laboratory Manual: Biological Sciences 112/113 (Spring 1998). University of Southern California
Department of Biological Sciences, 1995.
Brigitte Steinmetz (John Adams Middle School, Santa Monica – Malibu Unified School District)
Page 2
8/15/2004
PREDATOR AND PREY
(From Biological Sciences 112/113 Laboratory Manual (Spring 1998), University of Southern California)
Purpose:
1. To study a simulation of a predator-prey relationship between two populations each with a considerable
amount of variation.
2. To study what is meant by natural selection.
3. To explain why changing environments change population characteristics.
4. To show what is meant by "the pressures of the predator populations 'mold' prey populations."
5. To demonstrate how the prey populations also "mold" the predator populations.
6. To explain why variation within a species is the "raw material" of natural selection.
Materials:
Predators: 5 morphs -fork, spoon, knife, forceps, and hand
Prey: 5 morphs -black, brown, white, red, green beans
Mouths: Styrofoam cups Stopwatch
Clipboard and pencil Calculator optional
Introduction:
Variations occur spontaneously within a species in a given population. Certain individuals in any species are
better equipped or adapted in some ways to obtain food, escape predators, or physiologically utilize food more
efficiently. Some members of a species are more successful than others in building nests or attracting mates or
in the case of flowering plants, in attracting pollinators. The individuals with characteristics that increase their
capacity to obtain nutrients, escape predators, withstand adverse climatic conditions, or attract mates, will have
more of a chance of surviving and reproducing. Inheritable variations that give any organism improved chances
of surviving until reproductively mature and then improve chances of leaving viable offspring are called
adaptations.
In this exercise, the predators and the prey have selective forces on each other and therefore each influences the
survival of the other. Well adapted species will survive and reproduce and the poorly adapted species will die,
perhaps without leaving any offspring.
The students are the predators using the 5 aforementioned morphs of feeding tools to identify your particular
species. The prey are the 5 morphs of beans which are scattered in the environment (grass). The predators who
capture less than the mean number of prey captured are considered extinct (natural selection at work). Some of
the remaining students whose species become extinct will be reborn as another species with a different feeding
mechanism, representing the offspring of the successful predators of the previous generation.
The number of surviving prey are calculated and doubled for the next generation. The hunt continues for up to
four generations if time permits.
Procedure:
a. Divide the students into 5 equal groups. Example: 15 students divide into 5 groups with 3 students in
each.
b. Give all the students in each group a particular predator. Ex: 3 students get a fork, 3 a knife, 3 a pair of
forceps and 3 use their hands. Also give each student a cup.
c. Count out 100 beans of each color. You can save time by doing this before lab.
d. Arm the T.A. with a watch with a second hand or a stopwatch.
e. Line the students up around the periphery of the area to be the "hunting grounds". Use an area of lawn
(or artificial grass) around 10’ x 10’.
f. Mix the beans and spread them out on the ground.
g. Tell the students to start and time them. Give them approximately 40 seconds to gather a good amount
of beans.
h. The students should pick up the beans with their utensil and drop the beans into their cups (mouths).
They shouldn't shovel or scoop the beans into the cup. A reasonable amount of jostling among the
students is considered normal competition and is to be expected. Knocking other students' utensils or
upsetting their cups (making them vomit) is not normal competition and should be discouraged!
i. When time is up, have the students stop; discourage hunting after hours.
j. Have the students count the number of beans of each color (and the total number of beans.) Have the
students tell the T .A. how many beans they have. The T .A. should keep track of the beans on the score
sheet. When all the students have reported their bean counts the T.A. totals the number of beans of each
color that each type of predator “ate." Then total the number of each color of bean that survived, that is,
(total beans of each color) - (number of beans captured) = number of survivors.
Ex: If 23 green beans are captured in generation 1, 100 -23 = 77 green survivors.
k. Have the surviving beans "reproduce" by adding 1 bean to the population for every surviving bean of
each morph. Ex: As in the above example, 77 green beans survived so 77 new green beans are added to
the population for a total of 154 green beans in generation 2. Keep track of the populations; you need the
numbers to calculate survivorship in the following rounds. Get the students to count out the new beans
that you remembered to bring with you for reproduction purposes.
l. Calculate the average number of beans captured per predator. Add the total number of beans captured
and divide by the number of predators.
m. Announce the average (round off to the nearest whole bean.) Any predator who had less than the
average becomes extinct. Have these students turn in his/her utensil.
n. Allow the "successful" predators to reproduce proportionally (which isn't always easy with 15 -20
students.)
Ex. 1: 4 hands, 3 forceps and 1 spoon survived. There are 8 students who just became extinct and can be
used as the reproduced predators. Hand out 4 new hands, 3 new forceps and 1 new spoon.
Certain morphs will become extinct rather quickly. In either case, keep track of the new total of each
predator morph.
o. Do a second round by repeating steps h -n.
p. Try to go 4 rounds so that distinct trends will emerge. Certain predators will do well while others will
become extinct. Beans generally won't become extinct although some will do better than others. In the
lawn, the green beans will of course do better than the other morphs. Artificial grass can give different
results. If the beans are the same size, shape and texture, color will be the important factor in survival.
Lentils have an extra advantage as do peas (flat and round respectively). Pinto beans might do well in
dirt.
q. Graphs should be generated for the post lab.
First Generation
A. Predator survivorship
Number of prey killed per individual predator, number of surviving predators, and population of next
generation.
White
Number of Prey Killed
Red Brown Black
Green
Total Prey
Killed
Average
kills per
individual
# of
Surviving
Predators
Population
of next
generation
Population
Hand
Spoon
Forceps
Fork
Knife
B. Prey Survivorship
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
Red
Brown
Black
Green
Population
Total # Killed
Number of
Survivors
Population of next
generation
Second Generation
A. Predator survivorship
Number of prey killed per individual predator, by prey type.
White
Population
Hand
Spoon
Forceps
Fork
Knife
Number of Prey Killed
Red Brown Black
Green
Total Prey
Killed
Average
kills per
individual
# of
Surviving
Predators
Population
of next
generation
B. Prey Survivorship
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
Red
Brown
Black
Green
Population
Total # Killed
Number of
Survivors
Population of next
generation
Third Generation
A. Predator survivorship
Number of prey killed per individual predator, by prey type.
White
Number of Prey Killed
Red Brown Black
Green
Total Prey
Killed
Average
kills per
individual
# of
Surviving
Predators
Population
of next
generation
Population
Hand
Spoon
Forceps
Fork
Knife
B. Prey Survivorship
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
Population
Total # Killed
Number of
Survivors
Population of next
generation
Red
Brown
Black
Green
Addendum to Predator and Prey Lab
First Generation
A. Predator survivorship
Number of prey killed per individual predator, number of surviving predators, and population of next generation.
Number of participating students = 25 (5 for each type of predator).
Below is an example of a chart I would use to collect data from the students (on board).
Explanation of table:
Total # of prey killed is total number of each type of prey killed by all individuals.
Average kills per individual = Total Prey Killed ÷ # of predators
For Hand: 91 total prey killed ÷ 5 hand predators = 18.2 (we round to nearest whole # to get 18)
Total Average kills per individual for all = Added avg. kills per individual (18+20+13+8+4 = 63) ÷ total# of types of
predators (5); so, 63 ÷ 5 = 12.6…nearest whole # = 13.
Predators who had less than 13 average kills go extinct.
For this example, we will say that 1 Hand, 1 Spoon, 2 Forceps, 3 Forks, 4 Knives went extinct. If this is the case, then the
following # of survivors are: 4 Hands, 4 Spoons, 3 Forceps, 2 Forks, 1 Knife.
To get the population of the next generation we include the surviving predators + their offspring (to keep the students
involved we reproduce proportionately). For example, in this case 11 students became extinct. So, we need to assign those
students offspring. For this example, I will assign 4 new hands, 4 new spoons, 2 forceps, 1 fork. I explain that the knife
cannot have an offspring because only one survived. There must be a minimum of two survivors to mate.
Population
White
Number of Prey Killed
Red Brown Black
Green
Total Prey
Killed
Hand
18
21
22
20
10
91
Average
kills per
individual
18
Spoon
21
18
23
22
15
99
20
4
8
Forceps
16
11
17
15
8
67
13
3
5
Fork
12
9
6
10
2
39
8
2
3
Knife
4
5
3
5
2
19
4
1
1
# of
Surviving
Predators
4
Population
of next
generation
8
B. Prey Survivorship
Number of prey killed, number of survivors, and population of next generation, by prey type.
For this example, I used 100 of each color of bean.
Total # Killed = Total # killed by ALL predators
# of Survivors = Population – Total # Killed
Population of next generation = 2 x # of survivors
Population
White
100
Red
100
Brown
100
Black
100
Green
100
Total # Killed
71
64
71
72
37
Number of
Survivors
Population of next
generation
29
36
29
28
63
58
72
58
56
126
Brigitte Steinmetz (John Adams Middle School, Santa Monica-Malibu Unified School District)
Page 1
8/15/2004
Predator Prey Lab
Background: Some individuals in an ecosystem and species are better at surviving in their environment. Those
that are survive long enough to have babies. The characteristics that make them better at surviving are passed
on to the next generation (the next set of babies).
Investigation: Adaptations and Predator-Prey interactions.
Purpose: To discover the characteristics which help predators and prey survive the best in their environment.
Materials: Prey (beans) – white, red, brown, black, green. Predator – Hand, Spoon, Forceps, Fork, Knife
Data:
First Generation
A. Predator Survivorship (Ind = individual data; Grp = Group data)
Number of prey killed per individual predator, number of surviving predators, and population of next
generation.
Number of Prey Killed (individual & group data)
White
Ind
Grp
Red
Ind
Grp
Brown
Ind
Grp
Black
Ind
Green
Grp
Ind
Grp
Total
Prey
Killed
Group Data
Average
# of
kills per
Surviving
individual Predators
#Population
of next
generation
Population
Hand
Spoon
Forceps
Fork
Knife
B. Prey Survivorship (group data)
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
Red
Brown
Black
Green
# Population
Total # Killed
Number of
Survivors
Population of next
generation
Second Generation (with secondary predator introduced):
A. Predator Survivorship (Ind = individual data; Grp = Group data)
Number of prey killed per individual predator, by prey type.
Number of Prey Killed (individual & group data)
White
Ind
Population
Hand
Spoon
Forceps
Fork
Knife
Grp
Red
Ind
Grp
Brown
Ind
Grp
Black
Ind
Grp
Green
Ind
Grp
Total
Prey
Killed
Group Data
Average
# of
kills per
Surviving
individual Predators
#Population
of next
generation
B. Prey Survivorship (group data)
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
Red
Brown
Black
Green
Population
Total # Killed
Number of
Survivors
Population of next
generation
Third Generation
A. Predator Survivorship (Ind = individual data; Grp = Group data)
Number of prey killed per individual predator, by prey type.
Number of Prey Killed (individual & group data)
White
Ind
Grp
Red
Ind
Grp
Brown
Ind
Grp
Black
Ind
Green
Grp
Ind
Grp
Total
Prey
Killed
Group Data
Average
# of
kills per
Surviving
individual Predators
#Population
of next
generation
Population
Hand
Spoon
Forceps
Fork
Knife
B. Prey Survivorship (group data)
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
Red
Brown
Black
Green
Population
Total # Killed
Number of
Survivors
Population of next
generation
Analysis/Conclusion Questions (answer questions on a separate piece of paper):
1) As a class, graph your data (each student should do this on graph paper) showing the number of survivors for
each type of predator and each type of prey for all three generations. There should be two graphs (one for
predators and one for prey).
2) Which predator was better at surviving (had the most # of survivors)? Predators not good at surviving?
3) What characteristics made it hard for the predators to feed on the prey? Easy?
4) Which prey was better at surviving (had the most # of survivors)? Prey not good at surviving?
5) What characteristics made it hard for the prey to survive? Easy?
6) What happened when a certain type of predator or prey survived?
7) What happened when a certain type of predator or prey didn’t get enough food or got eaten and died?
8) What changed the number of predator survivors in the second round?
9) List at least two other things that we could do that would change the number of surviving predators and prey.
Predator Prey Lab
Answer Key from SDAIE science 2002-2003.
Background: Some individuals in an ecosystem and species are better at surviving in their environment. Those
that are survive long enough to have babies. The characteristics that make them better at surviving are passed
on to the next generation (the next set of babies).
Investigation: Adaptations and Predator-Prey interactions.
Purpose: To discover the characteristics which help predators and prey survive the best in their environment.
Materials: Prey (beans) – white, red, brown, black, green. Predator – Hand, Spoon, Forceps, Fork, Knife
Data:
First Generation
A. Predator Survivorship (Ind = individual data; Grp = Group data)
Number of prey killed per individual predator, number of surviving predators, and population of next
generation.
Number of Prey Killed (individual & group data)
White
Ind
Ind
23
8
26
12
12
Hand
Population
Grp
Red
Spoon
Forceps
Fork
Knife
Grp
Brown
Ind
Grp
2
10
0
9
14
Black
Ind
6
0
3
1
0
Grp
Total
Prey
Killed
0
0
0
0
0
34
19
29
23
27
Green
Grp
Ind
3
1
0
1
1
Group Data
# of
Average
Surviving
kills per
individual Predators
17
10
10
8
9
1
1
2
1
0
#Population
of next
generation
2
2
4
2
0
B. Prey Survivorship (group data)
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
# Population
Total # Killed
(population – killed)
Number of
Survivors
Population of next
generation
(survivors x 2)
Brown
Black
Green
100 100
Red
100
100
100
81
26
10
6
0
19
74
90
94
100
38
148
180
188
200
Second Generation (with secondary predator introduced):
A. Predator Survivorship (Ind = individual data; Grp = Group data)
Number of prey killed per individual predator, by prey type.
Number of Prey Killed (individual & group data)
White
Population
Ind
Hand
Spoon
Forceps
Fork
Grp
9
0
15
5
Red
Ind
Grp
8
0
2
10
Brown
Ind
Grp
8
0
0
2
Black
Ind
Grp
3
0
0
0
Grp
Total
Prey
Killed
0
0
0
0
48
0
17
17
Green
Ind
Group Data
Average
# of
kills per
Surviving
individual Predators
24
0
4
9
1
0
2
1
#Population
of next
generation
3
0
6
4
0
Knife
0
0
0
0
0
0
0
0
B. Prey Survivorship (group data)
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
Red
Brown
Black
Green
Population
38
148
180
188
200
Total # Killed
29
20
10
3
0
Number of
Survivors
(population – killed)
Population of next
generation
(survivors x 2)
8
128
170
185
200
16
256
340
370
400
Third Generation
A. Predator Survivorship (Ind = individual data; Grp = Group data)
Number of prey killed per individual predator, by prey type.
Number of Prey Killed (individual & group data)
White
Ind
Population
Hand
Spoon
Forceps
Fork
Knife
Grp
6
0
14
2
0
Red
Ind
Grp
Brown
Ind
31
0
33
8
0
Grp
Black
Ind
12
0
12
4
0
Grp
Total
Prey
Killed
2
0
2
14
0
63
0
68
36
0
Green
Grp
Ind
12
0
7
8
0
Group Data
# of
Average
Surviving
kills per
individual Predators
21
0
12
12
0
#Population
of next
generation
1
0
3
2
0
B. Prey Survivorship (group data)
Number of prey killed, number of survivors, and population of next generation, by prey type.
White
Red
Brown
Black
Green
Population
16
256
340
370
400
Total # Killed
22
72
28
27
18
Number of
Survivors
Population of next
generation
0
184
312
343
382
Analysis/Conclusion Questions (answer questions on a separate piece of paper):
1) As a class, graph your data (each student should do this on graph paper) showing the number of survivors for
each type of predator and each type of prey for all three generations. There should be two graphs (one for
predators and one for prey).
2) Which predator was better at surviving (had the most # of survivors)? Forceps Predators not good a surviving?
Knife.
3) What characteristics made it hard for the predators to feed on the prey? Camouflage – green been was in the
green grass. Size was small. Didn’t have anything to catch and keep the bean in its mouth. Easy? Size –
big. Other colors (i.e. white) were easy to see and so the predator could catch them. Hand, forceps had
more grip and could hold onto the bean.
4) Which prey was better at surviving (had the most # of survivors)? Green. Prey not good at surviving? White
5) What characteristics made it hard for the prey to survive? Different colors than the grass. Easy? Green grass
is same color as green bean.
6) What happened when a certain type of predator or prey survived? They reproduced (made babies).
7) What happened when a certain type of predator or prey didn’t get enough food or got eaten and died? Can’t
reproduce…they can’t make more babies for next generation.
8) What changed the number of predator survivors in the second round? 2nd predator that ate the 1st predator.
9) List at least two other things that we could do that would change the number of surviving predators and prey.
1) less of one species and more of the others.
2) change the prey’s color.
3) change the environment.