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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.
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).
Temperature-dependent sex determination (TSD) is a type of environmental sex determination in which the temperatures experienced during embryonic/larval development determine the sex of the offspring. [1] It is observed in reptiles and teleost fish, with some reports of it occurring in species of shrimp.
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 ...
Haeckel believed that to become a mammal, an embryo had to begin as a single-celled organism, then evolve into a fish, then an amphibian, a reptile, and finally a mammal. The theory was widely accepted, then disproved many years later.
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]
English: Amphibian Egg: 1. Jelly Capsule 2. Vitelline Membrane 3. Perivitelline Fluid 4. Yolk Plug 5. Embryo The jelly capsule is designed to protect the embryo from the outside environment. This capsule also prevents the egg from drying out. The vitelline membrane is a membrane surrounding the egg.
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.