Solved by a verified expert:WEEK 7 EXPERIMENT ANSWER
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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.
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
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
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