BIO153 Chapter 21
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
sexual dimorphism was developing over time in these species.
Please use the following information to answer the question(s) below. In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes. Which of these is closest to the allele frequency in the founding population?
0.1 a, 0.9 A
Please use the following information to answer the question below. A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. What is the estimated frequency of allele A in the gene pool?
0.50
Please use the following information to answer the question below. A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. What proportion of the population is probably heterozygous (Aa) for this trait?
0.50
(Figure 21.3) In a very large population, a quantitative trait has the distribution pattern shown in Figure 21.3. If the curve in Figure 21.3 shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations. Which of the following is (are) probably occurring? 1. immigration or emigration 2. directional selection 3. adaptation 4. genetic drift 5. disruptive selection
2 and 3
If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be
54%.
Anopheles mosquitoes, which carry the malaria parasite, cannot live above elevations of 5,900 feet. In addition, oxygen availability decreases with higher altitude. Consider a hypothetical human population that is adapted to life on the slopes of Mt. Kilimanjaro in Tanzania, a country in equatorial Africa. Mt. Kilimanjaro's base is about 2,600 feet above sea level and its peak is 19,341 feet above sea level. If the incidence of the sickle-cell allele in the population is plotted against altitude (feet above sea level), which of the following distributions is most likely, assuming little migration of people up or down the mountain?
Diagonal from top left corner to bottom right corner
Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?
Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted.
Which of the following is a true statement concerning genetic variation?
It must be present in a population before natural selection can act upon the population
What is true of natural selection?
Mutations occur at random; natural selection can preserve and distribute beneficial mutations
How can gene flow improve adaptation of population?
beneficial alleles are transferred to a new population
Evoluton
can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met.
You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to
cross your flies with flies from another lab
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?
directional selection
Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago), the evolution of life on this new island should have been most strongly influenced by
founder effect
Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing
gene flow.
In evolution, which driving factor most consistently requires a small population as a precondition for its occurrence?
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
genetic drift
If the original finches that had been blown over to the Galápagos Islands 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
genetic drift and founder effect
What is the result of adaptive evolution?
increase in frequency of alleles that provide reproductive advantage
Natural selection changes allele frequencies because some ________ survive and reproduce more successfully than others.
individuals
Sexual dimorphism is most often a result of
intersexual selection
"Until the agricultural revolution 10,000 years ago, people used to live in small populations with little gene flow between them. That is the best situation for rapid evolution," said Sewall Wright, one of the founders of population genetics.This conclusion on gene flow conflicts with Hardy-Weinberg equilibrium, which states that no gene flow means
no evolution
Please use the following information to answer the question(s) below. You are studying three populations of birds. Population A has 10 birds, of which 1 is brown (a recessive trait) and 9 are red. Population B has 100 birds, of which 10 are brown. Population C has 30 birds, and 3 of them are brown. Which population is most likely to be subject to the bottleneck effect?
population A
Please use the following information to answer the question(s) below. You are studying three populations of birds. Population A has 10 birds, of which 1 is brown (a recessive trait) and 9 are red. Population B has 100 birds, of which 10 are brown. Population C has 30 birds, and 3 of them are brown. In which population would it be least likely that an accident would significantly alter the frequency of the brown allele?
population B
Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer, or more, than this have reduced fitness. Which of the following terms best describes this situation?
stabilizing selection
Which of the following is most likely to produce an African butterfly species in the wild whose members have one pattern?
stabilizing selection
Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus,
the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change
What is the founder effect?
when a few individuals become isolated from a larger population, and their gene pool differs from that source population
What is a population in biology?
when a group of individuals of the same species live in the same area and interbreed