Deck 3: The Modern Synthesis

Question 1

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, 20% Aa, and 20% aa
D) 60% AA, 30% Aa, and 10% aa

Answer 1

A

Question 2

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.

Answer 2

C

Question 3

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

A) A = 0.6 and a = 0.4
B) A = 0.5 and a = 0.5
C) A = 0.3 and a = 0.7
D) A = 0.4 and a = 0.6

Answer 3

A = 0.3 and a = 0.7

Question 4

Which of the following is true of phenylketonuria (PKU)?

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

Question 5

Imagine a population where A = 0.2 and a = 0.8. Assuming random mating, what is the frequency of each genotype among the zygotes of the next generation?

A) AA = 0.2, Aa = 0, and aa = 0.8
B) AA = 0.40, Aa = 0.16, and aa = 0.44
C) AA = 0.04, Aa = 0.32, and aa = 0.64
D) AA = 0.40, Aa = 0.30, and aa = 0.60

Question 6

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) 4% aa, 64% Aa, and 16% AA

Question 7

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

A) a = 0.2 and A = 0.8
B) a = 0.4 and A = 0.6
C) a = 0.5 and A = 0.5
D) a = 0.6 and A = 0.4

Question 8

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

A) natural selection
B) nongenetic traits
C) mutation
D) random genetic drift

Question 9

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 = 0.20, Aa = 0.60, and AA = 0.20
C) aa = 0.20, Aa = 0.50, and AA = 0.30
D) aa = 0.25, Aa = 0.50, and AA = 0.25

Question 10

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 11

Which of the following is true of geneticists at the beginning of the twentieth century?

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

Question 12

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 13

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 14

Evolutionary change is best defined as a change in allele frequency over

A) generational time, including through mutation or drift.
B) generational time caused by selection, but not by mutation or genetic drift.
C) time caused by either drift or mutation, but not selection.
D) generational time that gives rise to a new species.

Question 15

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, followed by the averaging of the gene's effects during development.
C) mutation is constantly introducing new alleles, some of which will produce new phenotypes.
D) natural selection reduces variation.

Question 16

Which of the following is true of evolutionary change in a phenotype?

A) It results from change in the environment only.
B) It reflects change in the underlying genetic composition of a population.
C) It cannot be passed from parent to offspring.
D) Acquired phenotypic traits cause an underlying genetic change.

Question 17

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 18

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 19

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

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

Question 20

Why is mating in humans always effectively random even if individuals were to intentionally pick mates based on the absence of important genetic diseases?

A) Even if all the genetic loci are used in making a mate choice, the next generation randomizes the genes anyway.
B) In humans, there is no linkage, even between genes located near each other on the same chromosome.
C) The mating is still random across almost every one of the more than 22,000 loci across the human genome.
D) Humans lack genetic diversity; therefore, almost all human genes have a single allele.

Question 21

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 22

Which of the following increases genetic variation?

A) mutation
B) selection
C) extinction
D) fixation

Question 23

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

A) selection can use abundant hidden variation to move a population beyond its initial range of variation.
B) domestication of dogs involved a great deal of selection that whittled down the previously large diversity of wolves into the narrow range we call "dogs."
C) domestication of dogs involved a weakening of selection, and the result is a random range of dogs.
D) since dogs easily revert to wolf state if allowed to breed freely, dogs are mainly a cultural construct and are not genetically well defined.

Question 24

Which of the following decreases genetic variation?

A) mutation
B) selection
C) recombination
D) gene flow

Question 25

Of the following, which evolutionary process has the greatest chance of reducing genetic variation in a population across the greatest number of genes at once?

A) selection for a trait related to feeding
B) the sudden merging of two large populations that had been kept separate for several generations
C) selection for a trait related to reproduction
D) genetic drift in small populations

Question 26

Mate guarding of females by males in soapberry bugs probably functions to

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

Question 27

Which of the following is true 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) The alleles will compete to determine which one shapes the phenotype.

Question 28

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) behavioral mimicry.

Question 29

The genotype frequency for an allele, measured in terms of hypothetical gametes, is

A) the number of gametes of a particular allele divided by the total number of gametes.
B) the total number of gametes divided by the number of gametes of a particular allele.
C) the number of parents with either one or two copies of the allele divided by 2.
D) a random number under control of genetic drift.

Question 30

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

A) only two distinct alleles underlie the trait.
B) environmental variation smooths out the gaps between phenotypes.
C) sampling error when measuring the trait smooths out the variation.
D) continuous, smooth variation has a very high mutation rate.

Question 31

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 32

Which of the following statements about environmental variation is true?

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

Question 33

When no other force, such as natural selection, is operating, genotypic frequencies reach the Hardy-Weinberg equilibrium. The proportions for alleles A and a will be

A) freq(aa) = q² freq(Aa) = 2pq freq(AA) = p²
B) freq(aa) = q freq(Aa) = 2pq freq(AA) = p
C) freq(aa) = q² freq(Aa) = 2p²q freq(AA) = p²
D) freq(aa) = q² freq(Aa) = 2p²q² freq(AA) = p²

Question 34

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 35

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 36

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 37

Which of the following statements about natural selection is true?

A) It increases genetic variation because adaptations are produced.
B) It decreases genetic variation because the least adapted individuals are less likely to pass on their variation to the next generation.
C) It decreases genetic variation if selection is directional but increases genetic variation if selection is stabilizing.
D) It decreases genetic variation if selection is stabilizing but increases genetic variation if selection is directional.

Question 38

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

A) sudden increases in mutation rates are often induced by selection.
B) under genetic drift there is less variation and under selection there is more.
C) selection can expose hidden variation.
D) selection usually increases the randomness of mating, thus increasing variation.

Question 39

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 40

Which of the following is true of continuously varying characters?

A) They allow for blending of the effects of two genes, the blended version passed on to offspring.
B) They are likely to expose the genetic variation underlying a trait.
C) They always hide genetic variation.
D) They do not help to explain how variation is maintained.

Question 41

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 42

Local adaptations are called ________ constraints.

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

Question 43

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 44

Constraints on adaptation include

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

Question 45

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 46

When a population reaches fixation, which of the following is true?

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 47

Which of the following is true of genetic drift?

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

Question 48

Male soapberry bugs adjust their mate-guarding behavior in

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

Question 49

Genetic drift is strongest in

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

Question 50

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 51

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 52

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 53

How is continuous variation consistent with Mendelian inheritance?

Question 54

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 55

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 56

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 57

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 58

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 59

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 60

Which of the following statements about correlated characters is true?

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

Question 61

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

Question 62

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

Question 63

Explain how natural selection can shape flexible behavioral responses.

Question 64

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

Question 65

Explain why offspring are usually intermediate between their parents even though the nineteenth-century concept of blending inheritance was ruled out by the modern synthesis.

Question 66

Briefly describe five reasons that evolution does not always lead to the best possible phenotype, and give an example for each.