17. Due to various causes, including DDT poisoning, the population size of whooping cranes was reduced to about a dozen during the 1970s. The population size has since rebounded, and there are now hundreds of whooping cranes. Which of the following would you notexpect to see in the whooping crane population? A. Very low levels of genetic variation. B. Very few heterozygous individuals. C. Differences in allele frequency between current populations of cranes and historical populations. D. High heterozygosity. E. All of the above would be seen in whooping cranes.
18. A small number of birds arrive on an island from a neighboring larger island. This small population begins to adapt to the new food plants available on the island, and their beaks begin to change. About twice a year, one or two more birds from the neighboring island arrive. These new arrivals _____.
19. 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?
20. 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?
21. Over the past several decades, natural selection has caused populations of Staphylococcus aureus(an infectious wound bacterium) to evolve resistance to most antibiotics. If antibiotic use were stopped, what would you predict would happen to these S. aureuspopulations? A. They will go extinct without the antibiotic. B. The populations will begin colonizing new environments. C. The frequency of nonresistant forms will increase in these populations. D. The frequency of resistant forms will definitely increase in these populations.