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Reproduction is the biological process by which new individual organisms are produced. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: sexual and asexual, only the former is of interest to psychologists.

In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a bacterial cell into two daughter cells is an example of asexual reproduction. Asexual reproduction is not, however, limited to single-celled organisms. Most plants have the ability to reproduce asexually.

Sexual reproduction requires the involvement of two individuals, typically one of each sex. Normal human reproduction is a common example of sexual reproduction.

Sexual reproduction Edit

Main article: Sexual reproduction
Further information: Human reproduction
Hoverflies mating midair

Hoverflies mating in midair flight

Sexual reproduction is a biological process by which organisms create descendants that have a combination of genetic material contributed from two (usually) different members of the species. Each of two parent organisms contributes half of the offspring's genetic makeup by creating haploid gametes. Most organisms form two different types of gametes. In these anisogamous species, the two sexes are referred to as male (producing sperm or microspores) and female (producing ova or megaspores). In isogamous species the gametes are similar or identical in form, but may have separable properties and then may be given other different names. For example, in the green alga, Chlamydomonas reinhardtii, there are so-called "plus" and "minus" gametes. A few types of organisms, such as ciliates, have more than two kinds of gametes.

Most animals (including humans) reproduce sexually. Sexually reproducing organisms have two sets of genes for every trait (called alleles). Offspring inherit one allele for each trait from each parent, thereby ensuring that offspring have a combination of the parents' genes. Having two copies of every gene, only one of which is expressed, allows deleterious alleles to be masked, an advantage believed to have led to the evolutionary development of diploidy (Otto and Goldstein).


Main article: Allogamy



Self-fertilization (also known as autogamy) occurs in hermaphroditic organisms where the two gametes fused in fertilization come from the same individual. They are bound and all the cells merge to form one new gamete.

Mitosis and meiosis Edit

Mitosis and meiosis are an integral part of cell division. Mitosis occurs in somatic cells, while meiosis occurs in gametes.


Same-sex reproduction Edit

In recent decades, developmental biologists have been researching and developing techniques to facilitate same-sex reproduction [1]. The obvious approaches, subject to a growing amount of activity, are female sperm and male eggs, with female sperm closer to being a reality for humans, given that Japanese scientists have already created female sperm for chickens [2]. More recently, by altering the function of a few genes involved with imprinting, other Japanese scientists combined two mouse eggs to produce daughter mice [3].

Reproductive strategies Edit


Other types of reproductive strategies Edit

Main article: Semelparity and iteroparity

Polycyclic animals reproduce intermittently throughout their lives.

Semelparous organisms reproduce only once in their lifetime, such as some insects. Often, they die shortly after reproduction. This is a characteristic of r-strategists.

Iteroparous organisms produce offspring in successive (e.g. annual or seasonal) cycles, such as most mammals. Iteroparous animals survive over multiple seasons (or periodic condition changes). This is a characteristic of K-strategists.

Lottery principle Edit




See alsoEdit

Notes Edit

  1. [1] (timeline of research in the area of same-sex reproduction)
  2. Reference needed
  3. Reference needed
  4. Williams G C. 1975. Sex and Evolution. Princeton (NJ): Princeton University Press.

References Edit

  • "allogamy, cross-fertilization, cross-pollination, hybridization". GardenWeb Glossary of Botanical Terms (2.1). (2002). 
  • "allogamy". Stedman's Online Medical Dictionary (27). (2004). 

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