Some organisms are capable of asexual or sexual reproduction. Under favourable conditions, reproduction proceeds asexually. When conditions become more stressful reproduction switches to a sexual mode. Why?

Sexual reproduction is simple and more rapid allowing larger numbers of offspring to be produced.

Sexual reproduction requires two separate individuals, who can mutually provide nutrient support during stress.

Sexual reproduction produces individuals with new combinations of recombined chromosomes increasing diversity.

Asexual reproduction requires more energy.