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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.
Oviparity occurs in all birds, most reptiles, some fishes, and most arthropods. Among mammals , monotremes (four species of echidna , and the platypus ) are uniquely oviparous. In all but special cases of both ovuliparity and oviparity, the overwhelming source of nourishment for the embryo is the nutrients stored in the yolk, pre-deposited in ...
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
Male genitalia of Lepidoptera. The main component of the male reproductive system is the testicle, suspended in the body cavity by tracheae and the fat body.The more primitive apterygote insects have a single testis, and in some lepidopterans the two maturing testes are secondarily fused into one structure during the later stages of larval development, although the ducts leading from them ...
Over time amphibians have been found evolving to increasing internal fertilization. [citation needed] Within amphibians, it is common for high vertebrates to internally fertilize because of the transition from water to land during vertebrate evolution. There is an advantage for the amphibians who are internally fertilizing allowing for the ...
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.
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 ...
Females store the sperm until ovulation and internal fertilization take place, usually just prior to deposition in the spring. [7] Before the eggs are deposited, male mudpuppies leave the nest. [ 6 ] Once ready, the female deposits the eggs in a safe location, usually on the underside of a rock or log. [ 7 ]