Bio 122 ch. 21

0.42

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?

natural selection is limited to modifying structures

A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. The actual forelimbs of these mammals do not seem to be optimally arranged because

Genetic drift

Although each of the following has a better chance of influencing gene frequencies in small populations than in large populations, which one most consistently requires a small population as a precondition for its occurrence?

sexual dimorphism was developing over time

Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females and increasing larynx size in adult males, then

4, 2, 1, 5, 3

Arrange the following from most general (i.e., most inclusive) to most specific (i.e., least inclusive):

Stabilizing selection

Heterozygote advantage should be most closely linked to which of the following?

Gene variability: 0%, number of alleles: 1

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?

genetic drift and founder effect

If the original finches that had been blown over to the Galápagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of

Directional selection

In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population?

heterozygotes have 2 alleles

In the formula for determining a population's genotype frequencies, the pq in the term 2pq is necessary because

Individuals

Natural selection changes allele frequencies because some ________ survive and reproduce more successfully than others.

the reshuffling of alleles in sexual reproduction

No two people are genetically identical, except for identical twins. The main source of genetic variation among humans is

gene flow

Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing

intersexual selection

Sexual dimorphism is most often a result of

stabilizing selection

Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating

Diploidy

The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's diet has appropriate levels of the amino acid phenylalanine. What maintains the presence of this harmful allele in a population's gene pool?

Phenotype is often the result of compromise

The same gene that causes various coat patterns in wild and domesticated cats also causes a cross-eyed condition in these cats, the cross-eyed condition being slightly maladaptive. In a hypothetical environment, the coat pattern that is associated with crossed eyes is highly adaptive, with the result that both the coat pattern and the cross-eyed condition increase in a feline population over time. Which statement is supported by these observations?

genetic drift

There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from

Advantageous alleles do not arise on demand

There are those who claim that the theory of evolution cannot be true because the apes, which are supposed to be closely related to humans, do not likewise share the same large brains, capacity for complicated speech, and tool-making capability. They reason that if these features are generally beneficial, then the apes should have evolved them as well. Which of these provides the best argument against this misconception?

frequency-dependent selection

When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of

allele frequency does not change, homozygous and heterozygous may change

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus

Disruptive selection

Which of the following is most likely to produce an African butterfly species in the wild whose members have one of two strikingly different color patterns?