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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.
This capsule also prevents the egg from drying out. The vitelline membrane is a membrane surrounding the egg. Upon fertilization, this membrane splits off from the surface of the egg and the space between the vitelline membrane and the embryo is filled with perivitelline fluid. This fluid surrounds the embryo and yolk plug.
This is an accepted version of this page This is the latest accepted revision, reviewed on 6 March 2025. Class of animals This article is about the animal class. For other uses, see Reptile (disambiguation). Reptiles Temporal range: Late Carboniferous–Present Pre๊ ๊ O S D C P T J K Pg N Tuatara Saltwater crocodile Common box turtle Ladder snake Scientific classification Domain: Eukaryota ...
Reptiliomorpha (meaning reptile-shaped; in PhyloCode known as Pan-Amniota [2] [3]) is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians).
After internal fertilization and the habit of laying eggs in terrestrial environments became a reproduction strategy amongst the amniote ancestors, the next major breakthrough appears to have involved a gradual replacement of the gelatinous coating covering the amphibian egg with a fibrous shell membrane. This allowed the egg to increase both ...
The term ichthyopsida means fish-face or fish-like as opposed to the Sauropsida or lizard-face animals (reptiles and birds) and the mammals. [6] The group representing an evolutionary grade rather than a clade , the term anamniote is now used as an informal way of denoting the physical property of the group, rather than as a systematic unit.
The external location may also cause a reduction in the heat-induced contribution to the spontaneous mutation rate in male germinal tissue. [6] Sperm are the smaller of the two gametes and are generally very short-lived, requiring males to produce them continuously from the time of sexual maturity until death.
The young of ovoviviparous amphibians are sometimes born as larvae, and undergo metamorphosis outside the body of the mother. Modes of reproduction include [3] based on relations between zygote and parents: Ovuliparity: external fertilisation, as in arthropods, many bony fishes, and most amphibians