Heterogamy has a number of biological definitions:
  • In reproductive biology, heterogamy is the alternation of differently organized generations, applied to the alternation between parthenogenetic
    Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...

     and a sexual
    Sexual reproduction
    Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...

     generation. This type of heterogamy occurs for example in some aphid
    Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...

  • In cell biology, heterogamy is a synonym of anisogamy
    Anisogamy refers to a form of sexual reproduction involving the union or fusion of two dissimilar gametes — anisogamous, anisogamic,...

    , the condition of having differently sized male and female gamete
    A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...

    s produced by different sexes or mating types in a species.
  • In botany, a plant is heterogamous when it carries at least two different types of flowers in regards to their reproductive structures, for example male and female flowers or bisexual and female flowers. Stamen
    The stamen is the pollen producing reproductive organ of a flower...

    s and carpels are not regularly present in each flower or floret.
  • In a sociology
    Sociology is the study of society. It is a social science—a term with which it is sometimes synonymous—which uses various methods of empirical investigation and critical analysis to develop a body of knowledge about human social activity...

    , heterogamy refers to a marriage
    Marriage is a social union or legal contract between people that creates kinship. It is an institution in which interpersonal relationships, usually intimate and sexual, are acknowledged in a variety of ways, depending on the culture or subculture in which it is found...

     between two individuals that differ in a certain criterion, and is contrasted with homogamy
    -In sociology:Homogamy is marriage between individuals who are, in some culturally important way, similar to each other. Homogamy may be based on socio-economic status, class, gender, ethnicity, or religion...

     for marriage or union between partners that match according to that criterion. For example, ethnic heterogamy refers to marriages involving individuals of different ethnic groups. Age heterogamy refers to marriages involving partners of significantly different ages. Heterogamy and homogamy are also used to describe marriage or union between people of unlike and like sex (or gender) respectively.

The terms heterogametic and homogametic are related to heterogamy, but distinct.
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