Parthenogenesis - Types Of Parthenogenic Organisms, Cellular Mechanisms, Sexual Vs. Non-sexual Reproduction
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Parthenogenesis in animals refers to reproduction in which a new individual genetically identical to the parent develops from an unfertilized egg. The analogous event in plants, which results in seed formation without fertilization, is called agamospermy. Parthenogenesis is viewed as an aberration of sexual reproduction because animals that reproduce by parthenogenesis evolved from organisms that once reproduced sexually. In sexual reproduction female sex cells (ova) must be fertilized by male sex cells (typically sperm), for development to occur.
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The term parthenogenesis was first used in 1849 by the biologist Richard Owens. Although most animals reproduce sexually, some species of vertebrates and invertebrates reproduce by parthenogenesis. Of these species the most frequently studied are fish, reptiles, and insects. Parthenogenetic animals are classified as either facultative or obligate. Facultative parthenogens (usually invertebrates) c…
Parthenogens, unlike sexually reproducing animals, are faced with the unique problem of how to maintain a complete set of chromosomes. Chromosomes are cellular structures composed of DNA and protein that contain the genetic information cells need to function properly. In animals that reproduce sexually, reduction division (meiosis) occurs in cells destined to become eggs or sperm. Meiosis is the p…
Most organisms reproduce sexually because there is a competitive advantage in producing offspring with genetic contributions from two individuals rather than one. The genetic recombination which occurs during meiosis and on fertilization allows new gene combinations to come together in the next generation. Organisms with new gene combinations are more variable and offer more options for selection …
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