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Study Questions:
1. Why is relative fitness more important than fitness?
Study Questions:
1. Why is relative fitness more important than fitness?
It doesn’t matter how many offspring you produce, what matters is whether this is more than or less than the number OTHER
organisms in your population produce. There is an old colloquialism that is relevant. You don’t have to be faster than the bear. You
only have to be faster than the other people running from the bear. Absolute speed doesn’t matter, relative speed does.
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
a. What are the initial gene frequencies?
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
a. What are the initial gene frequencies? f(A) = f(AA) + f(Aa)/2 = 0.3 + 0.3/2 = 0.45; f(a) = f(aa) + f(Aa)/2 = 0.4 + 0.3/2 = 0.55
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
a. What are the initial gene frequencies? f(A) = f(AA) + f(Aa)/2 = 0.3 + 0.3/2 = 0.45; f(a) = f(aa) + f(Aa)/2 = 0.4 + 0.3/2 = 0.55
b. Is the population in HWE?
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
a. What are the initial gene frequencies? f(A) = f(AA) + f(Aa)/2 = 0.3 + 0.3/2 = 0.45; f(a) = f(aa) + f(Aa)/2 = 0.4 + 0.3/2 = 0.55
b. Is the population in HWE? If it were, then f(AA) should equal p2. f(A) = 0.45; (0.45)(0.45) = 0.2025. But our observed value = 0.3.
So, are observed population is NOT in HWE.
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
a. What are the initial gene frequencies? f(A) = f(AA) + f(Aa)/2 = 0.3 + 0.3/2 = 0.45; f(a) = f(aa) + f(Aa)/2 = 0.4 + 0.3/2 = 0.55
b. Is the population in HWE? If it were, then f(AA) should equal p2. f(A) = 0.45; (0.45)(0.45) = 0.2025. But our observed value = 0.3.
So, are observed population is NOT in HWE.
c. What are the relative fitness values?
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
a. What are the initial gene frequencies? f(A) = f(AA) + f(Aa)/2 = 0.3 + 0.3/2 = 0.45; f(a) = f(aa) + f(Aa)/2 = 0.4 + 0.3/2 = 0.55
b. Is the population in HWE? If it were, then f(AA) should equal p2. f(A) = 0.45; (0.45)(0.45) = 0.2025. But our observed value = 0.3.
So, are observed population is NOT in HWE.
c. What are the relative fitness values?
Divide each fitness value by the largest value; 0.4 in this case.
So,
0.4/0.4 = 1.0
0.2/0.4 = 0.5
0.1/0.4 = 0.25
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
a. What are the initial gene frequencies?
b. Is the population in HWE?
c. What are the relative fitness values?
d. What are the genotypic frequencies in the population of reproductive adults?
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
Relative fitness values
1.0
0.5
0.25
Reproducing Adults
0.3
0.15
0.1
= 0.55
Genotypic frequencies in Breeders:
0.3/0.55
= 0.55
0.15/0.55
= 0.27
0.1/0.55
= 0.18
= 1.0
a. What are the initial gene frequencies?
b. Is the population in HWE?
c. What are the relative fitness values?
d. What are the genotypic frequencies in the population of reproductive adults?
Multiply the genotypic frequencies in the zygotes by the relative fitness values, as shown above.
Then, add these values together and divide each value by this sum – this gives the proportional representation of each genotype in
this set of survivors. Round so that the values sum to 1.0.
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
Reproducing Adults
0.3
0.15
0.1
= 0.55
Genotypic frequencies in Breeders:
0.3/0.55
= 0.55
0.15/0.55
= 0.27
0.1/0.55
= 0.18
= 1.0
a. What are the initial gene frequencies?
b. Is the population in HWE?
c. What are the relative fitness values?
d. What are the genotypic frequencies in the population of reproductive adults?
e. What are the gene frequencies in the population of reproductive adults?
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
Reproducing Adults
0.3
0.15
0.1
= 0.55
Genotypic frequencies in Breeders:
0.3/0.55
= 0.55
0.15/0.55
= 0.27
0.1/0.55
= 0.18
= 1.0
a. What are the initial gene frequencies?
b. Is the population in HWE?
c. What are the relative fitness values?
d. What are the genotypic frequencies in the population of reproductive adults?
e. What are the gene frequencies in the population of reproductive adults?
f(A) = 0.55 + 0.27/2 = 0.685
f(a) = 0.18 + 0.27/2 = 0.315
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
Reproducing Adults
0.3
0.15
0.1
= 0.55
Genotypic frequencies in Breeders:
0.3/0.55
= 0.55
0.15/0.55
= 0.27
0.1/0.55
= 0.18
= 1.0
Gene Frequencies in Breeders
f(A) = 0.685
f(a) = 0.315
a. What are the initial gene frequencies?
b. Is the population in HWE?
c. What are the relative fitness values?
d. What are the genotypic frequencies in the population of reproductive adults?
e. What are the gene frequencies in the population of reproductive adults?
f. If there is random mating, what will be the genotypic frequencies in the next generation?
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
Reproducing Adults
0.3
0.15
0.1
= 0.55
Genotypic frequencies in Breeders:
0.3/0.55
= 0.55
0.15/0.55
= 0.27
0.1/0.55
= 0.18
= 1.0
Gene Frequencies in Breeders
f(A) = 0.685
Genotypic Frequencies in F1:
0.47
f(a) = 0.315
0.43
0.10
a. What are the initial gene frequencies?
b. Is the population in HWE?
c. What are the relative fitness values?
d. What are the genotypic frequencies in the population of reproductive adults?
e. What are the gene frequencies in the population of reproductive adults?
f. If there is random mating, what will be the genotypic frequencies in the next generation?
Plug the gene frequencies into the formula: p2 + 2pq + q2
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
Reproducing Adults
0.3
0.15
0.1
= 0.55
Genotypic frequencies in Breeders:
0.3/0.55
= 0.55
0.15/0.55
= 0.27
0.1/0.55
= 0.18
= 1.0
a. What are the initial gene frequencies?
b. Is the population in HWE?
c. What are the relative fitness values?
d. What are the genotypic frequencies in the population of reproductive adults?
e. What are the gene frequencies in the population of reproductive adults?
f. If there is random mating, what will be the genotypic frequencies in the next generation?
g. What agent of evolutionary change is at work?
2. Consider the following population of zygotes:
AA
Aa
aa
Genotypic Frequency
0.3
0.3
0.4
Prob. of survival
0.4
0.2
0.1
Reproducing Adults
0.3
0.15
0.1
= 0.55
Genotypic frequencies in Breeders:
0.3/0.55
= 0.55
0.15/0.55
= 0.27
0.1/0.55
= 0.18
= 1.0
a. What are the initial gene frequencies?
b. Is the population in HWE?
c. What are the relative fitness values?
d. What are the genotypic frequencies in the population of reproductive adults?
e. What are the gene frequencies in the population of reproductive adults?
f. If there is random mating, what will be the genotypic frequencies in the next generation?
g. What agent of evolutionary change is at work?
Natural Selection
3. Outline the modern synthetic theory of evolution.
3. Outline the modern synthetic theory of evolution.
Sources of Variation
Agents of Change
Mutation
Recombination
- independent assortment
- crossing over
Natural Selection
Drift
Mutation
Migration
Non-random mating
Variation
3. Outline the modern synthetic theory of evolution.
4. List the three components of fitness, and explain two trade-offs that necessarily occur because of limited energy budgets.
3. Outline the modern synthetic theory of evolution.
4. List the three components of fitness, and explain two trade-offs that necessarily occur because of limited energy budgets.
Three Components:
probability of survival to reproductive age
number of offspring
probability that offspring survive to reproduce
Trade Off #1: Survival vs, Reproduction: Invest in growth to increase survival, but decrease immediate reproduction… or invest in
immediate reproduction, but invest little in growth and reduce probability of survival.
Trade Off #2: Lots of small offspring that have little chance of survival, or a few large offspring with higher probability of survival.
3. Outline the modern synthetic theory of evolution.
4. List the three components of fitness, and explain two trade-offs that necessarily occur because of limited energy budgets.
5. Why can selection perfect an organism? Describe in terms of contradictory selective pressures, and provide an example.
3. Outline the modern synthetic theory of evolution.
4. List the three components of fitness, and explain two trade-offs that necessarily occur because of limited energy budgets.
5. Why can selection perfect an organism? Describe in terms of contradictory selective pressures, and provide an example.
The environment is complex; adaptations that optimize response to one variable may be bad with respect to other variables. For
example, large leaves are great for absorbing light, but they are bad because they lose lots of water. Leaf size will be a compromise
response to these two pressures; leaves will be larger in tropical rainforests where water loss is less stressful and leaf size can be
maximized; leaf size will be small in the desert because plants are in full light all day (no priority on large leaves) and water loss is
high.