Sexual reproduction: An overview
© Cambridge University Press 2013.Introduction: Reproduction is the production of offspring, propagating genes into the next generation, and exists in many forms within the animal kingdom. Each of these different strategies has advantages and disadvantages, but all strategies have evolved as the optimum for a particular species in a particular niche. Sexual reproduction, as opposed to asexual reproduction, in the majority of cases involves the recombination of DNA to result in the generation of unique individuals. Of these individuals, some will be better adapted to exist in the surrounding environment than others, and these better suited individuals are most likely to be more successful. Therefore, this process of evolution not only results in the success of the fittest but also leads to intense competition for the best mate to produce the ‘best’ next generation. For successful reproduction in mammals, i.e. the production of new viable offspring, there are many different stages that are essential not only in function but also timing. These stages include the production of functional gametes, appropriate behaviour to ensure the released gametes interact, a suitable environment for implantation and subsequent embryo development, birth to occur into a suitable environment and also for appropriate lactation to ensure the newborn is adequately provided for. Failure at any of these earlier stages can result in infertility ultimately failing to produce viable offspring, and in the worst case, threatens the life of the mother and of the fetus or newborn(s). Understanding how each of these events is regulated is critical for furthering our ability to influence these processes. This is critical not only to assist people who are unable to conceive naturally to have children, but also for other purposes such as to aid fertility in endangered species and to maximize reproduction for food production.