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Some documented species, specifically salamanders and geckos, that rely on obligate parthenogenesis as their major method of reproduction. As such, there are over 80 species of unisex reptiles (mostly lizards but including a single snake species), amphibians and fishes in nature for which males are no longer a part of the reproductive process. [41]
Fertilization is the fusion of gametes to produce a new organism. In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilization, or outside in the case of external fertilization.
[citation needed] Internal fertilization with many vertebrates (such as all reptiles, some fish, and most birds) occurs via cloacal copulation, known as cloacal kiss (see also hemipenis), while most mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization. [3] [4]
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.
The ZW sex-determination system is a chromosomal system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), the schistosome family of flatworms, and some reptiles, e.g. majority of snakes, lacertid lizards and monitors, including Komodo dragons.
Fertilization is the fusion of two gametes. [1] Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization. [2] Mating may also lead to external fertilization, as seen in amphibians, fishes and plants. For most species, mating is between two individuals of opposite sexes.
The female chooses a site in shallow water among vegetation, and lays a batch of up to 20,000 eggs, and the male simultaneously releases sperm, resulting in external fertilization. [44] The eggs form a thin, floating sheet which may cover an area of 0.5 to 1.0 m 2 (5.4 to 10.8 sq ft). The embryos develop best at water temperatures between 24 ...
An intromittent organ is any external organ of a male organism that is specialized to deliver sperm during copulation. [1] [2] Intromittent organs are found most often in terrestrial species, as most non-mammalian aquatic species fertilize their eggs externally, although there are exceptions.