Final answer:
The unequal sizes of male and female gametes have significant consequences on adult behavior in several species, leading to competitive and selective mating strategies among males, and sometimes elaborate nest-building among females, option 5: All of the above, except a, is the correct answer.
Step-by-step explanation:
The question being addressed is one that concerns the relevance of unequal gamete sizes in explaining adult behavior. In sexual reproduction, the size of the gametes is typically different, with the male gamete (sperm) being smaller than the female gamete (egg). This difference has significant implications for the behavior of adult animals.
Regarding the relevance of gamete size to adult behavior, option 2 suggests that because eggs are less abundant, males must compete for access to them. This leads to various behaviors such as fighting amongst males, mate guarding, or developing elaborate traits to attract females.
In some cases, females may take action in mating strategies, as described in option 3, by building structures to house their gametes for reproduction. This is a behavior directly influenced by the investment females make in producing larger gametes and caring for offspring.
While option 4 is a true statement about sexual reproduction, it does not adequately explain the effects on adult behavior connected to gamete sizes. Hence, the most comprehensive answer that links gamete sizes to adult behavior is option 5: All of the above, except a.