Problem 1: Many closely related animal species produce eggs of vastly different sizes. One trade-off of producing larger eggs is that fewer eggs can be produced. Despite the apparent simplicity of this trade-off, it is still unclear why both strategies (many small eggs and few large eggs) are maintained in groups of closely related species. What are some other life history traits besides offspring number that might be correlated with egg size, and under what environmental conditions might those traits be advantageous? Can you think of any reasons why species that live in the same habitats continue to exhibit reproductive patterns that vary so widely?
Problem 2: Some animals exhibit both sexual and asexual reproduction, depending on the environmental conditions they experience. Rotifers are a classic example of this phenomenon. Females can produce diploid eggs by mitosis that hatch soon after release. In this manner, rotifer populations can double within hours. These same females, under other conditions, can produce haploid eggs that form males if unfertilized and form females if fertilized. What might be the reason for the maintenance in rotifers of both sexual and asexual reproduction?
Problem 3: The Nassau grouper is popular in Asia, where restaurant goers can pick the grouper they want steamed for dinner from a selection of live fish swimming in tanks. Adult groupers can grow to large sizes (up to 3 feet long and 55 pounds), but those favored by restaurants are plate sized juvenile and young adult fish. How would you expect the removal of these younger, smaller fish to affect the life history evolution of the remaining population? How might life history parameters such as age and size at reproduction and investment in growth versus reproduction evolve in response to fishing pressures?