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Parthenogenesis is a form of reproduction where eggs develop without fertilization, resulting in unisexual species. This phenomenon is closely related with reproductive modes such as hybridogenesis, where fertilization occurs, but the paternal DNA is not passed on.
Parthenogenesis occurs naturally in some plants, algae, invertebrate animal species (including nematodes, some tardigrades, water fleas, some scorpions, aphids, some mites, some bees, some Phasmatodea, and parasitic wasps), and a few vertebrates, such as some fish, amphibians, and reptiles. This type of reproduction has been induced ...
The outer parts are known as the genitals or external genitalia, visible at birth in both sexes, [1] while the inner parts are referred to as internal genitalia, which in both sexes, are always hidden. [2] In plants, male reproductive structures include stamens in flowering plants, which produce pollen. [3]
Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization , brings more control to the female with reproduction. [ 1 ]
Parthenogenesis is a mode of asexual reproduction in which offspring are produced by females without the genetic contribution of a male. Among all the sexual vertebrates, the only examples of true parthenogenesis, in which all-female populations reproduce without the involvement of males, are found in squamate reptiles (snakes and lizards). [1]
Apomixis in plants is the formation of a new sporophyte without fertilization. It is important in ferns and in flowering plants, but is very rare in other seed plants. In flowering plants, the term "apomixis" is now most often used for agamospermy, the formation of seeds without fertilization, but was once used to include vegetative reproduction.
A few types of organisms, such as many fungi and the ciliate Paramecium aurelia, [11] have more than two "sexes", called mating types. Most animals (including humans) and plants reproduce sexually. Sexually reproducing organisms have different sets of genes for every trait (called alleles). Offspring inherit one allele for each trait from each ...
In amniotes – reptiles, birds, and mammals – the egg is enclosed with an outer layer, or amnion, which has led to further development of the oviduct.In reptiles, birds, and monotremes, the main part of the oviduct is a muscular tube, capable of considerable distension to transport the large eggs that are produced.