Chapter 20B

Question 1

Which of the following results in random allele
frequency changes in a population?

a) Natural selection
b) Heterozygote advantage
c) Genetic drift
d) Differential reproductive fitness

Answer 1

Genetic drift

Question 2

Genetic Drift (random changes in
allele frequencies) is greatest in…

A. Large populations
B. Small populations
C. Random mating populations

Answer 2

Small populations

Question 3

Which phrase most accurately
describes natural selection?

A. Non-random mating of individuals
B. Increase in an individual’s fitness
C. Differences in survival and/or reproduction
between individuals with different genotypes
D. Evolutionary change in a population

Answer 3

Differences in survival and/or reproduction
between individuals with different genotypes

Question 4

Natural selection that favors one extreme of the
phenotypic spectrum is known as __________.

a) directional selection
b) differential selection
c) disruptive selection
d) stabilizing selection

Answer 4

directional selection

Question 5

If the heritability of a trait is high,
which of the following is true?

A. The response will be greater with a low selection
pressure (s) than a high selection pressure.
B. With the same selection pressure (s), the response
will be greater for a trait with low heritability.
C. With the same selection pressure (s), the response
will be greater for a trait with high heritability.
D. The response to selection does not depend on
selection pressure (s).

Answer 5

With the same selection pressure (s), the response
will be greater for a trait with high heritability.

Question 6

Two populations of fish are in separate lakes. Each population has
different frequencies of alleles at a gene. A river forms between the
lakes, allowing fish to freely move between the lakes. What will be
the allele frequencies in the two lakes after 2 generations of random
mating between the lakes?

A. The allele frequencies in each lake will not change
B. Both lakes will have allele frequencies equal to the
frequency in one lake prior to the river forming
C. The allele frequencies will change in each lake,
but it will not be predictable
D. The allele frequencies in the two lakes will be the
same as each other, and intermediate between
what they were before the river formed

Answer 6

The allele frequencies in the two lakes will be the
same as each other, and intermediate between
what they were before the river formed

Question 7

Which of the following is least likely to
change allele frequencies?

A. Finite population size (genetic drift)
* Lose genetic variation in small populations
* Change allele frequencies when population size decreases dramatically
B. Natural selection in favor of one allele
* Directional selection leads to the fixation of one allele
C. Migration into a population
* Migrants can bring new alleles and change allele frequencies
D. Mutations creating new alleles
* Can change allele frequencies, but operates slowly
E. Non-random mating
* Genotype frequencies change (non-HWE), but allele frequencies stay the same

Answer 7

Non-random mating
* Genotype frequencies change (non-HWE), but allele frequencies stay the same

Question 8

Breeder’s equation?

Answer 8

R = S × h²

Question 9

Higher heritability means?

Answer 9

Stronger response to selection.

Question 10

Primary effects of migration?

Answer 10

Changes allele frequencies and equalizes between populations.

Question 11

After admixture, how many generations to restore HWE?

Answer 11

One generation of random mating.

Question 12

Does mutation alone greatly change allele frequencies?

Answer 12

No, effect is small.

Question 13

What leads to divergence?

Answer 13

Reproductive isolation.

Question 14

Consequence of divergence?

Answer 14

Speciation

Question 15

Which force least likely to change allele frequencies?

Answer 15

Non-random mating.

Question 16

Which forces can equalize allele frequencies?

Answer 16

Migration (gene flow).

Question 17

Which of the following is true?

A. The response to selection will be greater with a low
selection pressure (s) than a high selection pressure.
B. With the same selection pressure (s), the response
will be greater for a trait with lower heritability.
C. With the same selection pressure (s), the response
will be greater for a trait with higher heritability.
D. The response to selection does not depend on
selection pressure (s) or heritability.

Answer 17

With the same selection pressure (s), the response
will be greater for a trait with higher heritability.