The largest unit within which gene flow can readily occur is a
a. Population.
b. Species.
c. Genus.
d. Hybrid.

Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent?

a. Habitat isolation

b. Temporal isolation

c. Behavioral isolation

d. Gametic isolation

According to the punctuated equilibria model:

a. Given enough time, most existing species will branch gradually into new species.

b. Most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

c. Most evolution occurs in sympatric populations.

d. Speciation is usually due to a single mutation.

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?

a. The two forms interbreed often in nature, and their offspring survive and reproduce well.

b. The two forms live in similar habitats and have similar food requirements.

c. The two forms have many genes in common.

d. The two forms are very similar in appearance.