In human demography and population biology, fecundity is the actual reproductive rate of an organism or population, measured by the number of gametes (eggs), seed set, or asexual propagules. Fecundity is similar to fertility, the natural capability to produce offspring. A lack of fertility is infertility while a lack of fecundity would be called sterility.
Human demography considers only human fecundity which is often intentionally limited through contraception, while population biology studies all organisms. The term fecundity in population biology is often used to describe the rate of offspring production after one time step (often annual). In this sense, fecundity may include both birth rates and survival of young to that time step. Fecundity is under both genetic and environmental control, and is the major measure of fitness. Fecundation is another term for fertilization. Superfecundity or retrofecundity refers to an organism's ability to store another organism's sperm (after copulation) and fertilize its own eggs from that store after a period of time, essentially making it appear as though fertilization occurred without sperm (i.e. parthenogenesis).
Fecundity is important and well studied in the field of population ecology. Fecundity can increase or decrease in a population according to current conditions and certain regulating factors. For instance, in times of hardship for a population, such as a lack of food, juvenile and eventually adult fecundity has been shown to decrease (i.e. due to a lack of resources the juvenile individuals are unable to reproduce, eventually the adults will run out of resources and reproduction will cease).
Fecundity has also been shown to increase in ungulates with relation to warmer weather.
- Etienne van de Valle (adapted by), from the French section edited by Louis Henry (1982). "Fecundity". Multilingual demographic dictionary, English section, second edition. Demopaedia.org, International Union for the Scientific Study of Population. p. 621-1. Retrieved 8 February 2010.
- Eugene Grebenik (1958). "Fecundity". Multilingual demographic dictionary, English section. Prepared by the Demographic Dictionary Committee of the International Union for the Scientific Study of Population. Demopaedia.org, United Nations Department of Economic and Social Affairs (DESA). p. 621-1. Retrieved 8 February 2010.
- Berek JS and Novak E. Berek & Novak's gynecology. 14th ed. 2007, Philadelphia: Lippincott Williams & Wilkins. Pg. 1186
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