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Biology

Peter H. Raven, George B. Johnson, Kenneth A. Mason

Chapter 20

Genes Within Populations - all with Video Answers

Educators

Chapter Questions

02:30

Problem 1

Assortative mating
a. affects genotype frequencies expected under Hardy-Weinberg equilibrium.
b. affects allele frequencies expected under Hardy-Weinberg equilibrium.
c. has no effect on the genotypic frequencies expected under Hardy-Weinberg equilibrium because it does not affect the relative proportion of alleles in a population.
d. increases the frequency of heterozygous individuals above Hardy-Weinberg expectations.

Christina Sorrentino
Christina Sorrentino
Numerade Educator
03:23

Problem 2

When the environment changes from year to year and different phenotypes have different fitness in different environments
a. natural selection will operate in a frequency-dependent manner.
b. the effect of natural selection may oscillate from year to year, favoring alternative phenotypes in different years.
c. genetic variation is not required to get evolutionary change by natural selection.
d. None of the choices is correct.

Christina Sorrentino
Christina Sorrentino
Numerade Educator
02:40

Problem 3

Many factors can limit the ability of natural selection to cause evolutionary change, including
a. a conflict between reproduction and survival as seen
in Trinidadian guppies.
b. lack of genetic variation.
c. pleiotropy.
d. All of the choices are correct.

Christina Sorrentino
Christina Sorrentino
Numerade Educator
02:40

Problem 4

Stabilizing selection differs from directional selection because
a. in the former, phenotypic variation is reduced but the average phenotype stays the same, whereas in the latter both the variation and the mean phenotype change.
b. the former requires genetic variation, but the latter does not.
c. intermediate phenotypes are favored in directional selection.
d. None of the choices is correct.

Christina Sorrentino
Christina Sorrentino
Numerade Educator
01:37

Problem 5

Founder effects and bottlenecks are
a. expected only in large populations.
b. mechanisms that increase genetic variation in a population.
c. two different modes of natural selection.
d. forms of genetic drift.

Christina Sorrentino
Christina Sorrentino
Numerade Educator
01:15

Problem 6

Relative fitness
a. refers to the survival rate of one phenotype compared to that of another.
b. is the physical condition of an individual's siblings and cousins.
c. refers to the reproductive success of a phenotype.
d. None of the choices is correct.

Christina Sorrentino
Christina Sorrentino
Numerade Educator
02:39

Problem 7

For natural selection to result in evolutionary change
a. variation must exist in a population.
b. reproductive success of different phenotypes must differ.
c. variation must be inherited from one generation to the next.
d. All of the choices are correct.

Christina Sorrentino
Christina Sorrentino
Numerade Educator