WEEK 7 EXPERIMENT Evolutionary Change without Natural Selection

WEEK 7 EXPERIMENT ANSWER SHEET
Please submit to the
Week 7 Experiment dropbox no later than Sunday midnight.
SUMMARY OF ACTIVITIES FOR WEEK 7 EXPERIMENT ASSIGNMENT

Experiment 7 Exercise 1 – Evolutionary Change without
Natural Selection
Experiment 7 Exercise 2 – Evolutionary Change
with Natural Selection
Experiment 7 Exercise 3 – Evolution and Genetic
Drift

Before
starting, be sure you have read over the information in the Week 7 Experiment Introduction.

Materials Needed
For the
first two exercises you will need the following:

50 red M&Ms and 50 green M&Ms or 50 each of two items that are
distinguishable by color but are similar in size and texture (e.g., dimes
and pennies, two different color beads).
Four containers large enough to hold
the above items.

Experiment 7 Exercise 1: Evolutionary Change without Natural Selection
In this
first exercise, we are going to look for evidence of evolutionary change in a
population in the absence of natural
selection by looking at the change in allele frequencies over time in a
simulated population. We will start with a population of 50 individuals in which there are two alternate alleles (H
and h)
in equal proportions (each at a frequency of 0.5 or 50%). Individuals have the
possible genotypes: HH,
Hhor hh.
These two alleles do not
offer any selective advantage, so neither is selected for or against, meaning
they are neutral. We will record the
frequency of these alleles over 10 generations. Prior to advancing on to the
next generation, six alleles (= three individuals) will be removed at random.
Before you begin,
answer the following:
Question

What is your prediction
as to what will happen to the frequencies
(note that this is different than the number) of these two alleles over 10
generations? Word your prediction as an “if-then” statement based on the experiment design. (1 pts).

Procedure:

Let 50
M&M’s of one color (i.e. red) represent the dominant allele (H)
and 50 M&M’s of another color (i.e. green) represent the recessive allele (h).
Let one container represent the Habitat where random mating occurs.
Place all of the M&Ms (or other items) into this container. This is
your starting gene pool of your
“parent” population or Generation 0.
Label the other three containersHHfor
homozygous dominant individuals, Hh for heterozygous individuals
and hh for the homozygous recessive individuals. Notice that
individuals have two alleles.
Mix up your Habitat
well and without looking, select two
items (alleles) at a time; these two alleles represent a single individual. On a piece of paper, keep track of the genotypes of the individuals
withdrawn. For instance, if you draw one red and one green M&M, that
counts towards “Number ofHhindividuals.” If you draw two
red M&Ms, that counts towards “Number ofHHindividuals” and so on.
Continue drawing pairs and recording the results
until all items (alleles) have been withdrawn and sorted. Be sure to place
the “offspring” into the appropriate dish:HH, Hh, or hh. Note that the total number of
individuals will be half the total number of items because each individual
requires two alleles, so you will have 50 offspring (but 100 alleles). Record the number
of HH, Hhand hh individuals drawn for Generation 1 in Table 1 below.
Next count (or calculate) the total number of H and the total number of h
alleles for the first generation and record the number in Table 1 below in the columns
labeled “Number of H
Alleles” and “Number of h
Alleles.”
Add up the total number ofHalleles andhalleles for the first
generation and record this number in the column labeled “Total Number
of Alleles.” If you did everything correct, you should still
have 50 H alleles and 50 h alleles.This has
already been entered for you in the Table below for Generation 1.
Combine the HH,
Hhand hh individuals back into the Habitat container and mix well. Randomly remove three
pairs of alleles (= three individuals, six items) and set them aside.
Repeat steps D through H to obtain Generations 2
through 10. Remember to randomly remove threepairs of alleles each time.Because I know that each
generation will have six fewer
alleles, I have also entered the total number of alleles in the Table
below. Be sure that is the number your alleles add up
to!

Here is a photograph of
this process after six generations. The sixth generation has been distributed
into the HH, Hh and hh containers.
Note that dimes and pennies have been used.

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After entering your number of individuals and
allele counts for each generation, you now need to determine the allele frequencyofHandhfor each generation and record them
the Table below. To determine
allele frequency take:

# ofH/Total alleles in the generation
= Allele frequency ofH(express as a decimal)
# ofh/Total alleles in the generation
=Allelefrequency ofh

Note that the total number of alleles will change each
generation, but the frequency the H
allele plus the frequency of the h
allele should add up to 1.0 for each generation.

Table 1.
Results evolutionary change without
natural selection (2 pts).

Generation

Number of HH individuals

Number
of Hh individuals

Number
of hh individuals

Number
of H alleles

Number
of h alleles

Total
Number of alleles

Allele
Frequency of H

Allele
Frequency of h

1

50

50

100

0.5

0.5

2

94

3

88

4

82

5

76

6

70

7

64

8

58

9

52

10

46

Generate a line
graph of Allele frequency vs Generation. This means you need to graph
the last two columns of your data in the Table above. Paste your graph
below. Be sure to label your axes (3 pts).

Questions

Describe what your graph above depicts with
respect to the frequency of the two different alleles across generations(2 pts).

Was your prediction correct? Why or why not (1 pts)?

Define evolution. Are the
results of this simulation an example of evolution? Explain your answer. Cite any sources used (4 pts).

Experiment 7 Exercise 2: Evolution Change with Natural Selection
In this
second exercise, we will determine the effect that natural selection has on the frequency of two alleles which start
off in equal proportions (50:50) in the population. This time, individuals who
are hh die, meaning the homozygous recessive allele combination is lethal. These individuals will be
removed from the gene pool when they are drawn and will not contribute to the
following generation. This means that the h
allele is being selected against. Keep in mind that carriers of this lethal allele (e.g., those individuals that are Hh) are unaffected because the h allele is recessive.
Question
1.
What
is your prediction as to what will
happen to the frequencies of these two alleles over 10 generations? Word your
prediction as an “if-then” statement based on the experimental design. (1 pts).

Procedure:
A.
Return
ALL alleles to the Habitat container
and ensure that it contains 50 H
alleles and 50 h alleles. This is our
Generation 0.
B.
Use
the other three containers labeledHHfor homozygous dominant individuals, Hh
for heterozygous individuals and hh for the homozygous recessive
individuals.
C.
Mix
up your Habitat container well and
without looking, select two alleles
at a time; these two represent a single
individual. On a piece of paper, keep track of the type of individual withdrawn (HH, Hh
or hh).
D.
Continue
drawing pairs and recording the results until all alleles have been withdrawn
and sorted. Be sure to place the “offspring” into the appropriate dish:HH, Hh, or hh. Record the number of HH, Hh
and hh individuals drawn for Generation
1 in Table 2 below.
E.
Next
count (or calculate) the total
number of H and h alleles for the first generation and record the number in the
Table below.
F.
Add
up the number ofHalleles andhalleles
for the first generation and record this number in the column labeled
“Total Number of Alleles.” If you did everything correct, you
should still have 50 H alleles and 50 h alleles.This has already been entered for you in the
Table below for Generation 1.You
will need to enter this information for Generations 2-10, as it will change.
G.
Now
it is time for natural selection.
Remove all of the h alleles from the container labeled hh and discard them. These
individuals have died and cannot reproduce.
H.
Return
the alleles of the remaining HH and Hhindividuals back to the Habitat container.
I.
Repeat
steps D through H to obtain Generations 2 through 10. Remember that each time,
all hh
individuals die and are removed after you have counted them.
J.
After
entering your number of individuals and allele counts for each generation, you
now need to determine the allele
frequency ofHandhfor each generation and record them in
Table 2below.
Table
2. Results from
evolutionary change with natural selection (2 pts).

Generation

Number of HH individuals

Number
of Hh individuals

Number
of hh individuals

Number
of H alleles

Number
of h alleles

Total
Number of alleles

Allele
Frequency of H

Allele
Frequency of h

1

50

50

100

0.5

0.5

2

3

4

5

6

7

8

9

10

K. Generate a line graph of Allele frequency vs Generation #. This
means you need to graph the last two columns of your data in the Table above.
Paste your graph below. Be sure to label your axes (3 pts).

Questions
2. Describe what your graph above depicts with
respect to the frequency of the two different alleles across generations(2 pts).

3. Was your prediction correct?
Why or why not (1 pts)?

4.
Explain
why the h allele was not entirely
eliminated from the population (2 pts).

Based on
your earlier definition of evolution, are the results of this simulation
an example of evolution? Explain your answer (2 pts).

Experiment 7 Exercise 3: Mechanisms of Evolutionary Change
Be sure that
you have completed the suggested readings; your success on this exercise is
dependent on your understanding of evolutionary concepts!
Procedure

Open the following website:

BioMan Biology. No date. Biology Games and
Virtual Labs: Evolution
.com/GamesandLabs/EvoClassGames/aaevo.html”>http://biomanbio.com/GamesandLabs/EvoClassGames/aaevo.html

Click where it says Press Spacebar or Click Here to Continue! And click again to
continue.
Read over the instructions carefully, paying
particular attention to the controls. Notice that as you successfully
shoot the correct answer, you will need to reload.
Click again where it says Press Spacebar or Click Here to Continue!
Click on
Mechanisms and begin.

A statement will be shown at the bottom of the
screen.
Use the arrow keys to move to the correct term
and use the space to shoot it down. Remember to reload!
Keep playing until you are told “You have succeeded here earthling! But
can you save the rest of your planet?” Start over if you fail.

Record your %
correct and score in Table 3 below when you are done.
Feel free to repeat to improve
your score if you would like.
Reload the page to start over or click
on the link above to return to the start page.
Click where it says Press Spacebar or Click Here to Continue! And click again to
continue.
Review the instructions and click again where it
says Press Spacebar or Click Here
to Continue!
Click on
Mechanisms 2 and begin.

As before, a statement will be shown at the
bottom of the screen.
Use the arrow keys to move to the correct term
and use the space to shoot it down. Remember to reload!
Keep playing until you are told “You have succeeded here earthling! But
can you save the rest of your planet?” Start over if you fail.

Record your %
correct and score in Table 3 below when you are done.
Feel free to repeat to improve
your score if you would like.
Answer the questions
that follow.

Table 3. Results (2 pts)

% Correct

Score

Mechanisms

100

1003

Mechanisms 2

100

1006

Questions
1.
Match
the following statements with the correct term (5 pts)
a. Mutation f.
Bottleneck
b. Genetic drift g.
Founder effect
c. Gene flow h.
Immigration
d. Natural selection i. Emigration
e. Non-random mating j.
Speciation

____ Type
of genetic drift that occurs when a new colony is established, that by chance
is genetically different than the original population.
____ Can result in evolution by acting on
favorable traits.
____ Only male lions with large, thick manes are
able to breed.
____ Reproductive isolation of two populations
of penguins can result in this.
____ The loss or gain of alleles from a
population by the movement of individuals into or out of the population.
____ Movement
of individuals into a population, bringing with them new alleles.
____ Random
events that cause changes in gene frequencies.
____ Type
of genetic drift in which there is a drastic reduction in population size and a
change in allele frequencies.
____ The ultimate source of new alleles and
traits that natural selection can act on.
____ When individuals leave a population, taking
alleles along with them.

Week 7 Experiment Grading Rubric

Component

Expectation

Points

Experiment 7 Exercise 1

Collection of data and generation of a line graph correctly
labeled (Table 1 and graph of data).

5 pts

Demonstrates an understanding of evolutionary change without
natural selection (Questions 1-4).

8 pts

Experiment 7 Exercise 2

Collection of data and generation of a line graph correctly
labeled (Table 2 and graph of data).

5 pts

Demonstrates an understanding of evolutionary change with
natural selection (Questions 1-5).

8 pts

Experiment 7 Exercise 3

Success at Angry Aliens and an understanding
of the mechanisms of evolutionary change (Table 3).

2 pts

Demonstrates an understanding of the
various mechanisms of evolutionary change(Question 1).

5 pts

TOTAL

33
pts