Exam 25: Evolutionary Processes

Mutation is the only evolutionary mechanism that _____.

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?

Suppose 64% of a remote mountain village can taste phenylthiocarbamide (PTC)and must therefore have at least one copy of the dominant PTC taster allele.If this population conforms to Hardy-Weinberg expectations for this gene,what percentage of the population must be heterozygous for this trait?

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

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 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?

Which of the following is the most predictable outcome of increased gene flow between two populations?

Researchers (Helle et al. ,2004)analyzed rates of twin births in the Sami population of Northern Scandinavia during the eighteenth and nineteenth centuries.They found that (1)a baby born from a singleton pregnancy was more likely to survive to adulthood than a baby born from a twin pregnancy,and (2)the average number of offspring raised to adulthood was higher for women who had twins than for those who never had twins.These data suggest that in this population,human twinning rate was _____.

Wikelski and Romero (2003)found that large marine iguanas had higher reproductive success than smaller iguanas did.However,the large iguanas were generally in poor body condition because they could not eat enough;at higher temperatures their foraging efficiency improved,allowing them to eat more.Thus,Wikelski and Romero hypothesize that iguana size will _____ as global warming gradually increases air and water temperatures in the Galápagos Islands.

Figure 25.2 Use the following information when answering the corresponding question(s) Martin Wikelski and L.Michael Romero (Body size,performance and fitness in Galápagos marine iguanas,Integrative and Comparative Biology 43 [2003]:376-86)measured the snout-to-vent (anus)length of Galápagos marine iguanas and observed the percent survival of different-sized animals,all of the same age.Figure 25.2 shows the log snout-vent length (SVL,a measure of overall body size)plotted against the percent survival of these different size classes for males and females. -Examine Figure 25.2.What type of selection for body size appears to be occurring in these marine iguanas?

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.Which of the following could explain why males display more often?

Figure 25.4 -Refer to Figure 25.4.Male reproductive success,measured as the number of offspring surviving to adulthood (pupating),is found for two closely related beetle species and graphed above.Which of these statements would you expect to be true of sexual dimorphism in the two species?

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