ABSTRACT
This chapter focuses on aspects of reproductive physiology only, and aims to provide the reader elsewhere for further information regarding genetics, development and evolution. The two fundamental physiological processes of reproduction are asexual reproduction and sexual reproduction. In general, asexual reproduction is limited to the simpler invertebrate groups, e.g. protozoans, coelenterates etc. There are several forms of asexual reproduction, perhaps the simplest being binary fission. Sexual reproduction is often regarded as the better way of producing offspring, mainly because the offspring that are produced are not genetically identical to their parents, so variation is achieved. Sexual reproduction is dependent on the production of gametes. Gametes are produced from specialized cells called primordial germ cells. The mammalian testes are made up of hundreds of tubes called seminiferous tubules, which are the site of sperm production. The control of egg production is much better understood in mammals. Generally, egg production in mammals is cyclical in nature.
