Exam 23: Evolutionary Processes

Use the following information when answering the corresponding questions). Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They ident gene responsible for toxin production. The dominant allele T) codes for an enzyme that makes the toxin, and the recessive all t) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The genotypes of all individuals in the population are determined see chart) and used to determine the actual allele frequencies in the population. Figure 23.1 -Based on whether the population in Figure 23.1 is in Hardy- Weinberg equilibrium, the researchers had already noted that negligible mutation and migration existed in this milkweed population, and the toxin does not affect the butterflies that pollinate these plants. Which of the following would be a logical conclusion about this milkweed population?

Which of the following is true?

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid- 1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population?

Dark- eyed junco birds have white outer tail feathers that the males display during aggressive interactions and also during courtship displays. Males with more white in their tail are more likely to win aggressive interactions with other males, and females prefer to mate with males with more white in their tails. In the case of juncos, aggression fighting) by males is a type of selection; thus, we would expect that variation in reproductive success to be higher in and this species should exhibit _ sexual dimorphism.

Cystic fibrosis is a genetic disorder in homozygous recessives that causes death during the teenage years. If 9 in 10,000 newborn babies have the disease, what are the expected frequencies of the dominant A₁) and recessive A₂) alleles according to the Hardy- Weinberg model?

A biologist doing a long- term study on a wild spider population observes increased variation in silk thickness. She hypothesizes that the population is experiencing

A hurricane sweeps across the southern tip of Florida, killing salamanders randomly. Salamander colour is genetic, and, after the storm, scientists notice that the frequency of yellow- brown salamanders and Green- brown salamanders has changed significantly. This is an example of a _ and we would predict that 20 generations after the storm the population would show .

Use the following information when answering the corresponding questions). In 1983, a population of dark- eyed junco birds became established on the campus of the University of California, San Diego UCSD), which is located many miles from the junco's normal habitat in the mixed- coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails. Females have less white in their tails than males, and display it less often. Pamela J. Yeh. 2004. Rapid evolution of a sexually selected trait following population establishment in a novel habitat. Evolution 58[1]:166- 74.) -The UCSD campus male junco population tails were, on average, 36% white, whereas the tails of males from nearby mountain populations averaged 40-45% white. If this observed trait difference were due to a difference in the original colonizing population, it would be due to

For a biologist studying a small fish population in the lab, which Hardy- Weinberg condition is easiest to meet?

How do the founder effect and the immigration aspect of gene flow differ for the cheetah Acinonyx jubatus)?

Use the following information when answering the corresponding questions). In 1983, a population of dark- eyed junco birds became established on the campus of the University of California, San Diego UCSD), which is located many miles from the junco's normal habitat in the mixed- coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails. Females have less white in their tails than males, and display it less often. Pamela J. Yeh. 2004. Rapid evolution of a sexually selected trait following population establishment in a novel habitat. Evolution 58[1]:166- 74.) -The UCSD campus male junco population tails are about 36% white, whereas the tails of males from nearby mountain populations are about 40- 45% white. The founding stock of UCSD birds was likely from the nearby mountain populations because some of those birds overwinter on the UCSD campus each year. Population sizes on the UCSD campus have been reasonably large, and there are significant habitat differences between the UCSD campus and the mountain coniferous forests; UCSD campus has a more open environment making birds more visible) and a lower junco density decreasing intraspecific competition) than that in the mountain forests. Given this information, which of the following evolutionary mechanisms do you think is most likely responsible for the difference between the UCSD and mountain populations?

Consider the following two scenarios: 1) A flash- flood sweeps through an area and random lemmings are killed, resulting in a change in lemming phenotype in subsequent generations; 2) A flash- flood sweeps through an area and some lemmings are able to survive because they are able to hold their breath longer than other lemmings, resulting in a change in lemming phenotype in subsequent generations. What are the primary differences between the two scenarios?

In a population of parrots on an island, there is considerable variation in beak size. Parrots with small, thick beaks can efficiently eat locusts insect), while birds with long, thin beaks can efficiently eat beetles. Both food types are available on the island. Which of the following types of selection, and effects on phenotypic variation would you expect to see?

Mutation is the only evolutionary mechanism that

For biologists studying a large flatworm population in the lab, which Hardy- Weinberg condition is most difficult to meet?

Which of the following populations is most likely to be in Hardy-Weinberg equilibrium?

Which of the following best describes the effect of the migration of individuals into a population?

Which of the following is true with respect to natural selection and genetic drift?

Cystic fibrosis is a genetic disease caused by a recessive allele. The membrane protein involved in cystic fibrosis confers resistance to typhoid fever. Imagine that a drug- resistant form of typhoid fever becomes common worldwide, killing a significant proportion of the human population over a period of several decades. Which of the following would you expect to observe in the world population during this period?

Humans have domesticated a number of plants and animals. In the domestication process, a few individuals of a species are "captured" to have a starting population and then these are bred for many generations. This is an example of a and you would therefore predict that domesticated organisms would show .