![]() Genetic diversity may also lead to evolved defenses against parasites and disease. When the environment is going to turn cold, most species of aphids reproduce sexually, because sexual reproduction produces eggs that are freeze tolerant and can diapause during the winter (Simon et al. Aphids, for example, will favor asexual reproduction when their environment is stable. This idea becomes clear when we examine organisms that can reproduce both sexually and asexually. Genetic diversity within a group of offspring is advantageous as the local environment changes. Sexual reproduction increases the chances of acquiring favorable mutations and is unlikely to propagate deleterious ones. Genetic recombination allows an organism's offspring to be genetically diverse. The major advantage of sexual reproduction comes from genetic recombination. Despite the cost of losing half of the potential passage of genes to the next generation, sexual reproduction is much more common than asexual reproduction among animals because it provides several evolutionary advantages. This means that a sexually reproducing diploid animal only passes half of its total genes on to its offspring. In contrast, due to meiosis, diploid sexually reproducing animals have two copies of each chromosome but only pass one copy of each chromosome on to an egg or sperm cell. The Evolution of SexAsexually reproducing animals pass on all of their chromosomes, and consequently all copies of each gene, to their offspring. We move on to consider the evolution of mate choice, and then we describe the types of mating systems found in animals. In this article we first discuss why sexual reproduction exists, and how differences between males and females affect mating systems. ![]() When choosing mates, animals evolve species-typical strategies for maximizing their reproductive success - this results in considerable diversity among animal species in their mating patterns. ![]() To study these differences, scientists observe mating systems and describe how males and females come together. Males and females differ greatly in the investment each makes to reproduce, and may therefore approach mating with differing strategies. A mating system describes how males and females pair when choosing a mate. ![]()
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