Which of the following is not required for a behavioral trait to evolve by natural selection?
a. In each individual, the form of the behavior is determined entirely by genes.
b. The behavior varies among individuals.
c. An individual's reproductive success depends in part on how the behavior is performed.
d. Some component of the behavior is genetically inherited.

Although many chimpanzees live in environments with oil palm nuts, members of only a few populations use stones to crack open the nuts. The likely explanation is that

a. The behavioral difference is caused by genetic differences between populations.

b. Members of different populations have different nutritional requirements.

c. The cultural tradition of using stones to crack nuts has arisen in only some populations.

d. Members of different populations differ in learning ability.

Female spotted sandpipers aggressively court males and, after mating, leave the clutch of young for the male to incubate. This sequence may be repeated several times with different males until no available males remain, forcing the female to incubate her last clutch. Which of the following terms best describes this behavior?

a. Polygyny

b. Polyandry

c. Promiscuity

d. Certainty of paternity

A region of the canary forebrain shrinks during the nonbreeding season and enlarges when breeding season begins. This change is probably associated with the annual

a. Addition of new syllables to a canary's song repertoire

b. Crystallization of subsong into adult songs

c. Sensitive period in which canary parents imprint on new offspring

d. Elimination of the memorized template for songs sung the previous year