Chapter 22 (Homework)

Within a few weeks of treatment with the drug 3TC, a patient's HIV population consists entirely of 3TC-resistant viruses. How can this result best be explained?

A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.

Of the following anatomical structures, which is homologous to the wing of a bird?

Flipper of a cetacean

During drought years on the Galapagos, small, easily eaten seeds become rare, leaving mostly large, hard-cased seeds that only birds with large beaks can eat. If a drought persists for several years, what should one expect to result from natural selection?

More small-beaked birds dying than larger-beaked birds. The offspring produced in subsequent generations have a higher percentage of birds with large beaks.

Which statement best describes the evolution of pesticide resistance in a population of insects?

Offspring of insects that are genetically resistant to the pesticide become more abundant as the susceptible insects die off.

In a hypothetical environment, fishes called pike-cichlids are visual predators of algae-eating fish (i.e., they locate their prey by sight). If a population of algae-eaters experiences predation pressure from pike-cichlids, which of the following should least likely be observed in the algae-eater population over the course of many generations?

Selection for larger female algae-eaters, bearing broods composed of more, and larger, young

Scientific evidence documents the pattern of evolution. The evidence exists in a variety of categories, including direct observation of evolutionary change, the fossil record, homology, and biogeography. Sort the following examples into the correct categories.

direct observation of evolutionary change - development of drug resistance in bacteria fossil record - discovery of transitional forms of horses; discovery of shells of extinct species homology - same genetic code in fireflies and tobacco plants; vestigial pelvis in right whales; similarities in mammalian forelimbs biogeography - similarity of endemic island species to nearby mainland species; marsupial mammals in Australia

Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails, as do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are

examples of convergent evolution, and adaptations to a common environment.