The aphid family of insects, which is found throughout the world, spreads diseases to host plants and thus is widely considered to be destructive pests. During the autumn, when environmental conditions turn unfavorable to aphids, females produce eggs that hatch both male and female aphids, which then reproduce sexually. The genetic traits of this generation of aphids combine randomly, and with so many offspring the chances are very high that some will be hearty enough to survive the harsh fall and winter seasons. Eggs that are laid during the winter and that hatch in the spring, when environmental conditions turn favorable to the aphid population, produce only female offspring. In the absence of males, these female offspring then reproduce asexually. This form of reproduction occurs at a much quicker rate than sexual reproduction does.

Which is the best explanation for why aphids have evolved to reproduce asexually during the spring season?

Explanation

The fact that aphids rely on sexual reproduction during the harsh winter months is to ensure, through natural selection, that some of the population is hearty enough to survive. But during the gentler spring, when environmental conditions support a much larger population, their main goal is to generate as many offspring as possible, as quickly as possible. This goal is better achieved by asexual reproduction.

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