Deck 3: The Modern Synthesis

Question 1

Phenylketonuria (PKU)

A) can result in shortened limbs.
B) is caused by the substitution of one allele for another at a single locus.
C) is not a genetically inherited disease.
D) All of the above.

Answer 1

B

Question 2

Evolutionary change occurs

A) whenever mutation occurs.
B) whenever allelic frequencies change from one generation to the next.
C) whenever genetic drift is eliminated.
D) Both a and

Answer 2

D

Question 3

Which of the following cannot cause evolutionary change within a population?

A) Natural selection
B) Hardy-Weinberg forces
C) Mutation
D) Random genetic drift

Answer 3

B

Question 4

Imagine a population where 20 individuals are aa, 40 are Aa, and 40 are AA. What are the allelic frequencies?

A) a = .2 and A = .8
B) a = .4 and A = .6
C) a = .5 and A = .5
D) a = .6 and A = .4

Question 5

For most continuously varying characters, offspring are intermediate between their parents because

A) of blending inheritance.
B) genetic transmission involves faithful copying of the genes themselves and their reassembly into different combinations in zygotes.
C) mutation is constantly introducing new alleles, some of which will produce new phenotypes.
D) natural selection reduces variation.

Question 6

To understand how Mendelian genetics helps to explain evolution, we need to look closely at what happens to genes in populations that are undergoing natural selection. This is the domain of

A) primatology.
B) evolutionary ecology.
C) human variation.
D) population genetics.

Question 7

Peas were a useful subject for Mendel's experiments because they have a number of

A) discontinuous traits.
B) mating strategies.
C) maladaptations.
D) canalized behaviors.

Question 8

Imagine a population where A = .2 and a = .8. Assuming random mating, what is the frequency of each genotype among the zygotes of the next generation?

A) AA = .2, Aa = 0, and aa = .8
B) AA = .40, Aa = .16, and aa = .44
C) AA = .04, Aa = .32, and aa = .64
D) AA = .40, Aa = .30, and aa = .60

Question 9

Which of the following is correct?

A) Selection can produce change when no variation is present in a population.
B) Selection cannot change the frequency of different phenotypes.
C) The strength and direction of selection depend on the environment.
D) The strength of selection is determined by dominant alleles.

Question 10

Consider a population of 20 aa, 32 Aa, and 48 AA individuals. Selection acts against the lethal recessive homozygote (aa) before adulthood. After selection, survivors mate randomly. What are the genotypic frequencies of the next generation?

A) 25% aa, 50% Aa, and 25% AA
B) All AA
C) 4% aa, 16% Aa, and 64% AA
D) None of the above.

Question 11

Which of the following statements is correct?

A) Hidden variation is not always present in continuously evolving traits.
B) Selection causes genotypic frequencies to reach equilibrium in one generation, and the distribution of phenotypes does not change.
C) Selection can lead to cumulative, long-term change.
D) Genetic variation is always expressed as phenotypic variation.

Question 12

Imagine a population where there are 20 aa individuals, 50 Aa individuals, and 30 AA individuals. Imagine that selection acts against both homozygotes such that neither homozygote survives to adulthood. What is the frequency of each genotype in the next generation of zygotes?

A) aa = 0, Aa = 1.0, and AA = 0
B) aa = .20, Aa = .60, and AA = .20
C) aa = .20, Aa = .50, and AA = .30
D) aa = .25, Aa = .50, and AA = .25

Question 13

Imagine a population of 0 AA, 60 Aa, and 40 aa individuals. What is the frequency of each allele in this population?

A) A = .6 and a = .4
B) A = .5 and a = .5
C) A = .3 and a = .7
D) A = .4 and a = .6

Question 14

What are the genotypic frequencies of the following population: 60 AA, 120 Aa, and 20 aa individuals?

A) 30% AA, 60% Aa, and 10% aa
B) 60% A and 40% a
C) 60% AA, 120% Aa, and 20% aa
D) None of the above.

Question 15

What are the allelic frequencies of the following population: 0 AA, 100 Aa, and 100 aa individuals?

A) 50% A and 50% a
B) 0% A and 100% a
C) 25% A and 75% a
D) 33% A and 67% a

Question 16

At the beginning of the twentieth century, geneticists

A) thought that inheritance was fundamentally discontinuous.
B) argued that Mendelian genetics supported Darwin's idea that adaptation occurs through the accumulation of small variations.
C) agreed that evolution proceeded by the gradual accumulation of small changes.
D) believed that genes had no discernible effect on phenotypes.

Question 17

Consider a population of 20 AA, 40 Aa, and 40 aa individuals. A is a dominant allele causing death before reproductive age. What are the genotypic frequencies of the next generation after selection?

A) All AA individuals
B) All aa individuals
C) 50% AA and 50% aa individuals
D) 25% AA and 75% aa individuals

Question 18

The modern synthesis refers to

A) the combination of Mendelian and blending inheritance.
B) the combination of anthropology and biology.
C) the combination of modern genetics and Darwinism.
D) the combination of modern anthropology with animal behavior.

Question 19

Evolutionary change in a phenotype

A) results from change in the environment only.
B) reflects change in the underlying genetic composition of a population.
C) cannot be passed from parent to offspring.
D) Both a and

Question 20

Sexual reproduction by itself

A) can change allelic frequencies.
B) can cause evolutionary change.
C) can change genotypic frequencies.
D) both b and

Question 21

For male soapberry bugs, behavioral plasticity is costly because

A) males must cooperate with other males to guard females.
B) flexibility requires longer appendages.
C) males will sometimes make mistakes about the local sex ratio and behave inappropriately.
D) flexible males have to grow larger and therefore need more food.

Question 22

Mutation can maintain variation because

A) every mutation results in adaptation.
B) directional selection is constantly working.
C) a considerable amount of variation is protected from selection.
D) the rates of mutation are very high.

Question 23

Mate guarding of females by males in soapberry bugs probably functions

A) to protect the females from harassment by other females.
B) to protect the females from predators.
C) to stop other males from mating with them.
D) to stop the females from eating.

Question 24

Natural selection can move a population beyond its initial range of variation if there is

A) mutation.
B) fixation.
C) hidden variation.
D) both a and

Question 25

Low rates of mutation can maintain variation in a population because many different genotypes generate intermediate phenotypes that are favored by ________ selection.

A) stabilizing
B) disruptive
C) directional
D) All of the above.

Question 26

Environmental variation

A) affects genotypic expression of characters.
B) tends to blur together the phenotypes associated with different genotypes.
C) does not direct selection.
D) has no effect on phenotype.

Question 27

Characters are more likely to exhibit continuous variation when

A) there are no environmental effects.
B) they are affected by alleles at more than one locus.
C) inheritance is blending rather than particulate.
D) there are only two alleles.

Question 28

Continuously varying characters

A) are affected by genes at only one locus.
B) have a large effect on the phenotype.
C) can be greatly affected by the environment.
D) do not help to explain how variation is maintained.

Question 29

Which of the following decreases genetic variation?

A) Mutation
B) Selection
C) Recombination
D) Gene flow

Question 30

Some male soapberry bugs adjust their mate-guarding behavior in response to the local environment. Males guard females more when

A) females are relatively abundant.
B) females are relatively scarce.
C) the sex ratio is skewed toward females.
D) the sex ratio is balanced.

Question 31

An organism expresses fewer antipredator tactics when the number of predators in the environment is low. This is an example of

A) behavioral canalization.
B) behavioral plasticity.
C) behavioral localization.
D) behavioral control.

Question 32

Natural selection can move a population beyond its initial range of variation because

A) there is hidden variation.
B) alleles for extreme phenotypes are not concentrated in any one individual.
C) there is no hidden variation.
D) both a and

Question 33

Natural selection

A) increases genetic variation because adaptations are produced.
B) decreases genetic variation because the most adapted individuals transmit the most characters to the next generation.
C) decreases genetic variation if selection is directional but increases genetic variation if selection is stabilizing.
D) decreases genetic variation if selection is stabilizing but increases genetic variation if selection is directional.

Question 34

The fact that all modern breeds of dog stem from wild wolves is evidence that

A) selection can move a population beyond its initial range of variation.
B) there is plenty of hidden variation.
C) selection is weak.
D) Both a and b are correct.

Question 35

The phenotypic frequencies of a character will form a smooth, bell-shaped curve because of

A) hidden variation.
B) environmental variation.
C) sampling variation.
D) mutational variation.

Question 36

Which of the following increase(s) genetic variation?

A) Mutation
B) Selection
C) Recombination
D) Both a and c

Question 37

Within a few thousand generations, wolves were transformed into a variety of domestic dogs; this transformation was due to

A) genetic drift.
B) disequilibrium.
C) mutation.
D) hidden variation.

Question 38

An organism expresses antipredator tactics regardless of the number of predators in the environment. This is an example of

A) behavioral canalization.
B) behavioral plasticity.
C) behavioral localization.
D) both a and

Question 39

When genes at many loci affect a character,

A) the trait is more likely to occur in a smooth distribution.
B) natural selection cannot act on the character.
C) the environment is less likely to affect the character.
D) both a and c are correct.

Question 40

How is variation maintained?

A) There is blending during sexual reproduction.
B) Mutations are deleterious.
C) New variation is slowly added by mutation.
D) The genetic composition of offspring is a replica of their parents.

Question 41

Consider the following population: 30 AA individuals, 50 Aa individuals, and 20 aa individuals. Is this population in Hardy-Weinberg equilibrium? Explain your answer.

Question 42

Behaviors are more likely to be canalized if

A) there is no genetic control of the behavior.
B) the behavior is seen in a variety of environments.
C) the behavior is seen in environments that are the same.
D) phenotypes vary.

Question 43

Constraints on adaptation include

A) uncorrelated characters.
B) equilibrium.
C) local adaptations.
D) population genetics.

Question 44

Genetic drift can

A) cause isolated populations to become more similar to one another.
B) cause isolated populations to diverge from one another.
C) lead to genotyping of populations.
D) lead to karyotyping of populations.

Question 45

Natural selection cannot make an elephant run as fast as a cheetah and fly like a bird. This is an example of

A) a correlated response to selection.
B) disequilibrium.
C) physical constraints on natural selection.
D) fixation.

Question 46

Consider the following population: 40 aa, 30 Aa, and 30 AA individuals. What is the frequency of the a allele? Imagine that all of the recessive homozygotes die before reproductive age and that all other genotypes survive and produce equal numbers of offspring. What is the frequency of the a allele in the next generation? Explain your answers.

Question 47

When a population reaches fixation,

A) disequilibrium has occurred.
B) it has lost one of the two alleles that code for a character.
C) the mean value of a correlated character has changed.
D) mutation has added new variation to the population.

Question 48

During a drought on Daphne Major, ground finches with thinner beaks would have been at an advantage over the birds that lacked this trait. However, because beak depth was favored by natural selection, beak width also increased. This is an example of how selection on one character can cause other characters to change in a ________ direction.

A) positively correlated
B) fixated
C) maladaptive
D) plastic

Question 49

Genetic drift is strongest in

A) small populations.
B) large populations.
C) medium-size populations.
D) populations out of equilibrium.

Question 50

The compound eye cannot evolve into the camera-type eye because

A) natural selection does not change adaptations.
B) the compound eye is always superior to the camera-type eye.
C) the compound eye is a local optimum.
D) the camera-type eye is a local optimum.

Question 51

Genetic drift always causes

A) changes in gene frequencies that are random with respect to adaptation.
B) adaptive changes in gene frequencies.
C) maladaptive changes in gene frequencies.
D) no change in gene frequencies.

Question 52

The character of "behavioral flexibility" evolved in the soapberry bug because it

A) affected reproductive success.
B) occurs only in stable environments.
C) was not passed down from father to son.
D) made behaviorally flexible males stronger.

Question 53

Although it would be advantageous for animals to be large enough to be invulnerable to predators, but agile enough to leap considerable distances, ________ make(s) this evolutionarily impossible.

A) behavioral plasticity
B) physical constraints
C) genetic drift
D) gene flow

Question 54

The environment changes so that most individuals in a population are not well adapted to the environment. This is an example of

A) a local optimum.
B) disequilibrium.
C) environmental drift.
D) genetic drift.

Question 55

Humans have a nearly insatiable appetite for sugar, fat, and salt because

A) we are in perfect equilibrium with regard to such appetites.
B) these appetites are always adaptive.
C) such appetites were adaptive in ancient environments.
D) these appetites are adaptive in our modern environment.

Question 56

How is continuous variation consistent with Mendelian inheritance?

Question 57

A correlated response to selection occurs when selection

A) indirectly increases a trait that has no effect on survival.
B) directly increases a trait that has a negative effect on survival.
C) is disruptive.
D) is stabilizing.

Question 58

Correlated characters

A) can occur because some genes affect more than one character.
B) change independently.
C) are always positively related.
D) make natural selection longer.

Question 59

Male soapberry bugs adjust their mate-guarding behavior

A) in places where the environment is stable.
B) in places where the environment is variable.
C) in colder climates.
D) in wetter climates.

Question 60

Local adaptations are called ________ constraints.

A) optimal
B) fixed
C) developmental
D) genetic

Question 61

Briefly describe five reasons that evolution does not always lead to the best possible phenotype.

Question 62

Explain why natural selection cannot evolve a camera-type eye from a compound eye.

Question 63

Explain how natural selection can shape flexible behavioral responses.

Question 64

Explain why offspring are usually intermediate between their parents even though blending inheritance is not true.

Question 65

How can small population size affect gene frequencies? When is fixation reached?

Question 66

Explain how natural selection can move a population beyond its initial range of variation.