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The egg is not retained in the body for most of the period of development of the embryo within the egg, which is the main distinction between oviparity and ovoviviparity. [1] 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 developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell (spermatozoon). [1] Once fertilized, the ovum becomes a single diploid cell known as a zygote.
Male carrying eggs Tadpole. The common midwife toad (Alytes obstetricans) is a species of midwife frog in the family Alytidae (formerly Discoglossidae). It is found in Belgium, France, Germany, Luxembourg, the Netherlands, Portugal, Spain, Switzerland, and the United Kingdom (although, in the latter, only as an introduction).
Ovoviviparous animals develop within eggs that remain within the mother's body up until they hatch or are about to hatch. It is similar to viviparity in that the embryo develops within the mother's body. Unlike the embryos of viviparous species, ovoviviparous embryos are nourished by the egg yolk rather than by the mother's body. [22]
Animals, including mammals, produce gametes (sperm and egg) through meiosis in gonads (testicles in males and ovaries in females). Sperm are produced by the process of spermatogenesis and eggs are produced by oogenesis. These processes are outlined in the article gametogenesis.
In many sharks the eggs hatch in the oviduct within the mother's body and the embryos are nourished by the egg's yolk and fluids secreted by glands in the walls of the oviduct. [19] The Lamniforme sharks practice oophagy, where the first embryos to hatch consume the remaining eggs and sand tiger shark pups cannibalistically consume neighbouring ...
Veterinary obstetrics are the obstetrical methods used in veterinary medicine, which are quite different from those of human medicine. Veterinary obstetrics is a branch of veterinary medicine that deals with medical and surgical care together with manipulations of the female animals in breeding , gestation , labor , puerperium (postpartum ...
External fertilization is a mode of reproduction in which a male organism's sperm fertilizes a female organism's egg outside of the female's body. [1] It is contrasted with internal fertilization, in which sperm are introduced via insemination and then combine with an egg inside the body of a female organism.