Exam 25: Evolutionary Processes

Two frog populations (same species)living in two neighboring lakes sing slightly different courtship songs.Increased irrigation makes the land between the two lakes wetter,allowing frogs to expand their ranges to the area between the lakes.Females in both populations prefer loud frogs to quieter frogs,but do not distinguish between the two slightly different songs.Assuming that courtship song differences have a genetic basis,predict what will likely happen to the songs of the two frog populations.

Genetic drift occurs in a population.Which of the following statements might be 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?

Figure 25.1. Use the following information when answering the following question(s). Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not.They identify the gene responsible for toxin production.The dominant allele (T)codes for an enzyme that makes the toxin,and the recessive allele (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. -Based on whether the population in Figure 25.1 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?

Figure 25.3 -Which of the graphs (Fig 25.3)best represents the relationship between the intensity of directional selection and the genetic variation present within a population?

Figure 25.1. Use the following information when answering the following question(s). Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not.They identify the gene responsible for toxin production.The dominant allele (T)codes for an enzyme that makes the toxin,and the recessive allele (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. -Refer to Figure 25.1.Is this population in Hardy-Weinberg equilibrium?

In Kerr and Wright's experiment with 96 fruit-fly populations,only 4 males and 4 females bred in each generation.After 16 generations,73% of their populations had only one allele present for the bristle morphology gene.Which of the following would you expect to occur if they allowed 10 males and 10 females to breed in each generation?

Which sex typically has more extreme sex-selected characteristics: males or females? Why? Give an example.

Three-spined stickleback fish (Gasterosteus aculeatus)show substantial heritable variation in gill-raker length.Fish caught in open water tend to have longer gill rakers and eat different foods than do those caught in shallower water.Longer gill rakers appear to function better for capturing open-water prey,while shorter gill rakers function better for capturing shallow-water prey.Which of the following types of selection is most likely to be found in a large lake (open water in middle and shallow water around the sides)with a high density of these fish?

Use the following information when answering the corresponding question(s). 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 do 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. ) -Refer to the paragraph on dark-eyed junco birds.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 most likely be due to _____.

In 1986 a nuclear power accident in Chernobyl,USSR (now Ukraine),led to high radiation levels for miles surrounding the plant.The high levels of radiation caused elevated mutation rates in the surviving organisms,and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since.Based on your understanding of evolutionary mechanisms,which of the following most likely occurred in the rodent populations following the accident?

In a small population of alpine foxes,you observe increased ear length over a 10-year period.Can you conclude that increase in ear length is advantageous in this population?

A rare species of newt is being studied by a young evolutionary biologist.She observes that female newts lay unusually large yolky eggs,but they abandon their nests as soon as the eggs are laid.Males,on the other hand,defend the territory around the nest and regularly bring the baby newts insects to feed on.The males also sleep with the babies to keep them warmer during cool nights.Which of the following statements is MOST LIKELY to be true of these newts?

Currently the only predators of Galápagos marine iguanas are Galápagos hawks.Iguana body size is not correlated with risk of hawk predation,although small iguanas can sprint faster than large iguanas.If predators (e.g. ,cats)that preferably catch and eat slower iguanas are introduced to the island,iguana body size is likely to _____ in the absence of other factors;the iguanas would then be under _____ selection.

An earthquake decimates a ground-squirrel population.The surviving population happens to have broader stripes on average than the initial population.If broadness of stripes is genetically determined,what effect has the ground-squirrel population experienced during the earthquake?

Cystic fibrosis is a genetic disorder in homozygous recessive (ff)humans that typically causes death in the early 30s.Over time,we would expect the f allele frequency to _____ for this trait.

A beneficial point mutation occurs in a plant ovule,which is fertilized.The seed matures,falls to the ground,and starts to grow.Is the plant's population likely to show evolutionary change as a result of this mutation? Why or why not?

A biologist doing a long-term study on a wild spider population observes increased variation in silk thickness.Which of the following could the spider population be experiencing?

In some jacana species,males take care of the eggs and young,and females compete among themselves for territories that contain one to several males.Female jacanas are significantly larger than males.Which of these statements would you predict to be true of this bird species? 1)Male jacana fitness is primarily limited by ability to take care of eggs and raise young. 2)Female jacana fitness is limited by the number of males in her territory with which a female mates. 3)Variation in reproductive success should be greater in male jacanas than in females. 4)Variation in reproductive success should be greater in female jacanas than in males. 5)Males and females have equal variation in reproductive success.

Why doesn't inbreeding depression,by itself,cause evolution?