Question 1

In small populations,frequencies of certain alleles may change by chance alone.Such random change in the frequency of alleles is called

Accepted Answer

A) mutation. 
B) migration. 
C) genetic drift. 
D) nonrandom mating. 
E) selection. 
A) mutation. 
B) migration. 
C) genetic drift. 
D) nonrandom mating. 
E) selection.

Question 2

Migration and hybridization between individuals of adjacent populations causes gene _______.

Accepted Answer

A) blending 
B) flow 
C) mutation 
D) dominance 
A) blending 
B) flow 
C) mutation 
D) dominance

Question 3

In disruptive selection,over time

Accepted Answer

A) a population goes extinct. 
B) the most extreme outliers of a population are eliminated (e.g. ,the largest beaks and smallest beaks are eliminated). 
C) the population is strongly selected for in one direction (e.g. ,larger beak size). 
D) the population is strongly selected for in two directions (e.g. ,larger beak size and smaller beak size). 
E) a population increases its variation (E.g. ,a wide selection of all beak sizes). 
A) a population goes extinct. 
B) the most extreme outliers of a population are eliminated (e.g. ,the largest beaks and smallest beaks are eliminated). 
C) the population is strongly selected for in one direction (e.g. ,larger beak size). 
D) the population is strongly selected for in two directions (e.g. ,larger beak size and smaller beak size). 
E) a population increases its variation (E.g. ,a wide selection of all beak sizes).

Question 4

Small,drab,early reproduction is favored.

Accepted Answer

A) directional selection 
B) stabilizing selection 
C) disruptive selection 
D) guppies with pike cichlids and killifish 
E) guppies with killifish 
A) directional selection 
B) stabilizing selection 
C) disruptive selection 
D) guppies with pike cichlids and killifish 
E) guppies with killifish

Question 5

The total of all the alleles of all the genes in a population can be thought of as

Accepted Answer

A) an allele mixture. 
B) a gene pool. 
C) a genetic melting pot. 
D) a genome. 
E) variant genes. 
A) an allele mixture. 
B) a gene pool. 
C) a genetic melting pot. 
D) a genome. 
E) variant genes.

Question 6

One extreme of an array of phenotypes is favored.

Accepted Answer

A) directional selection 
B) stabilizing selection 
C) disruptive selection 
D) guppies with pike cichlids and killifish 
E) guppies with killifish 
A) directional selection 
B) stabilizing selection 
C) disruptive selection 
D) guppies with pike cichlids and killifish 
E) guppies with killifish

Question 7

The recessive phenotype of a trait occurs in 20% of a population.There are no selection pressures affecting this trait.What would be the expected frequency of the heterozygote genotype after six generations of continued non-selection?

Accepted Answer

A) 0.2 
B) 0.306 
C) 0.447 
D) 0.494 
E) 0.553 
A) 0.2 
B) 0.306 
C) 0.447 
D) 0.494 
E) 0.553

Question 8

A gene is represented in the gene pool of a population of 10,000 individuals by a dominant (W)and recessive allele (w).If the initial frequency of W in the pool is 0.7,how many generations of complete selection against it would be required to eliminate all W alleles from the population? Assume that there is no mutation and the population meets all other Hardy-Weinberg conditions.

Accepted Answer

A) 1 
B) 2 
C) 5 
D) 20 
E) can never be eliminated 
A) 1 
B) 2 
C) 5 
D) 20 
E) can never be eliminated

Question 9

Darwin proposed that natural selection occurs in an environment by

Accepted Answer

A) favoring heritable features that make the organism better suited to survive and reproduce. 
B) producing a constant number of offspring while in that environment. 
C) surviving for a fixed amount of time. 
D) resisting the environment and keeping the environment from changing. 
E) favoring those individuals with the most favorable acquired characteristics. 
A) favoring heritable features that make the organism better suited to survive and reproduce. 
B) producing a constant number of offspring while in that environment. 
C) surviving for a fixed amount of time. 
D) resisting the environment and keeping the environment from changing. 
E) favoring those individuals with the most favorable acquired characteristics.

Question 10

About 80% of the alleles present in thoroughbred horses can be dated back to 31 known ancestors from the late eighteenth century.As a result,one would expect

Accepted Answer

A) low rates of mutation. 
B) many polymorphic alleles. 
C) little variation in physiology and behavior. 
D) Hardy-Weinberg equilibrium. 
E) random mating. 
A) low rates of mutation. 
B) many polymorphic alleles. 
C) little variation in physiology and behavior. 
D) Hardy-Weinberg equilibrium. 
E) random mating.

Question 11

The phenomenon in which rare alleles become more common in new populations is called

Accepted Answer

A) founder effect. 
B) gene flow. 
C) genetic drift. 
D) assortative mating. 
E) mutation. 
A) founder effect. 
B) gene flow. 
C) genetic drift. 
D) assortative mating. 
E) mutation.

Question 12

Coloration in the peppered moth (Biston betularia)is determined by a single gene with two alleles showing complete dominance.Dark moths are homozygous dominant or heterozygous for the gene,light moths are homozygous recessive.In a sample of 100 moths,you determine that 64 of the moths are dark.According to the Hardy-Weinberg rule,the expected frequency of the dominant allele is ____.

Accepted Answer

A) 0.4 
B) 0.36 
C) 0.6 
D) 0.64 
E) cannot be determined 
A) 0.4 
B) 0.36 
C) 0.6 
D) 0.64 
E) cannot be determined

Question 13

The midrange of an array of phenotypes is favored.

Accepted Answer

A) directional selection 
B) stabilizing selection 
C) disruptive selection 
D) guppies with pike cichlids and killifish 
E) guppies with killifish 
A) directional selection 
B) stabilizing selection 
C) disruptive selection 
D) guppies with pike cichlids and killifish 
E) guppies with killifish

Question 14

The text discusses sickle-cell anemia,which is a classic example of

Accepted Answer

A) founder effect. 
B) genetic bottleneck. 
C) point mutation. 
D) heterozygote advantage. 
E) heterozygosity. 
A) founder effect. 
B) genetic bottleneck. 
C) point mutation. 
D) heterozygote advantage. 
E) heterozygosity.

Question 15

The Hardy-Weinberg equilibrium conditions for populations of organisms result in

Accepted Answer

A) polymorphic alleles. 
B) assortive mating. 
C) natural selection. 
D) maintenance of recessive alleles in the gene pool. 
E) no evolutionary changes. 
A) polymorphic alleles. 
B) assortive mating. 
C) natural selection. 
D) maintenance of recessive alleles in the gene pool. 
E) no evolutionary changes.

Question 16

Cheetahs have been through a genetic bottleneck;evidence for this is that

Accepted Answer

A) little natural selection occurs in this species. 
B) the body is long,thin,and graceful. 
C) there is very little genetic variability. 
D) these cats are members of an endangered species. 
E) they originally came from small areas of Africa. 
A) little natural selection occurs in this species. 
B) the body is long,thin,and graceful. 
C) there is very little genetic variability. 
D) these cats are members of an endangered species. 
E) they originally came from small areas of Africa.

Question 17

Which of the following statements about disruptive selection is false?

Accepted Answer

A) It involves multi-gene inheritance. 
B) It results in polymorphism. 
C) It results in a bimodal distribution of phenotypes within a population. 
D) It increases heterozygosity within the population. 
E) It selects against individuals with intermediate phenotypes. 
A) It involves multi-gene inheritance. 
B) It results in polymorphism. 
C) It results in a bimodal distribution of phenotypes within a population. 
D) It increases heterozygosity within the population. 
E) It selects against individuals with intermediate phenotypes.

Question 18

The key point in Darwin's proposal is that the ___________ imposes the conditions that determine the results of selection and thus the direction of selection.

Accepted Answer

A) parent 
B) gene 
C) individual 
D) environment 
A) parent 
B) gene 
C) individual 
D) environment

Question 19

Which one of the following is not an agent of natural evolutionary change?

Accepted Answer

A) mutation 
B) migration 
C) genetic drift 
D) non-random mating 
E) artificial selection 
A) mutation 
B) migration 
C) genetic drift 
D) non-random mating 
E) artificial selection

Question 20

Natural selection as a mechanism of evolution that acts on variants within populations and ultimately leads to the evolution of different species was proposed by

Accepted Answer

A) Mendel. 
B) Lyell. 
C) Malthus. 
D) Darwin. 
E) Founder. 
A) Mendel. 
B) Lyell. 
C) Malthus. 
D) Darwin. 
E) Founder.

Exam 20: Genes Within Populations

In small populations,frequencies of certain alleles may change by chance alone.Such random change in the frequency of alleles is called

Migration and hybridization between individuals of adjacent populations causes gene _______.

In disruptive selection,over time

Small,drab,early reproduction is favored.

The total of all the alleles of all the genes in a population can be thought of as

One extreme of an array of phenotypes is favored.

The recessive phenotype of a trait occurs in 20% of a population.There are no selection pressures affecting this trait.What would be the expected frequency of the heterozygote genotype after six generations of continued non-selection?

Darwin proposed that natural selection occurs in an environment by

About 80% of the alleles present in thoroughbred horses can be dated back to 31 known ancestors from the late eighteenth century.As a result,one would expect

The phenomenon in which rare alleles become more common in new populations is called

The midrange of an array of phenotypes is favored.

The text discusses sickle-cell anemia,which is a classic example of

The Hardy-Weinberg equilibrium conditions for populations of organisms result in

Cheetahs have been through a genetic bottleneck;evidence for this is that

Which of the following statements about disruptive selection is false?

The key point in Darwin's proposal is that the ___________ imposes the conditions that determine the results of selection and thus the direction of selection.

Which one of the following is not an agent of natural evolutionary change?

Natural selection as a mechanism of evolution that acts on variants within populations and ultimately leads to the evolution of different species was proposed by

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