Sexual Reproduction:
The great majority of animals reproduce through sexual reproduction, though there are some species that can switch between sexual and asexual reproduction as circumstances demand. That raises an interesting question: given the obvious benefits of asexual reproduction, why do most animals reproduce sexually?
Natural selection is all about getting as many of your genes into the next generation as possible. As such, sexually-reproducing animals would seem to have an obvious disadvantage compared to asexually-reproducing animals. After all, if you’re reproducing asexually and your offspring are clones of you, then each offspring carries 100% of your genes. But if you’re reproducing sexually, each offspring carries only 50% of your genes. Asexual reproduction, then, would seem to be the way to go, since you can get twice as many genes into the next generation per offspring if you reproduce asexually.
So, to repeat the question: Why do the great majority of animals reproduce sexually?
When asked this question, my students occasionally suggest that sexual reproduction is more fun. That may be, but the answer doesn’t really address the question.