Search results
Results from the WOW.Com Content Network
Monotremes (/ ˈ m ɒ n ə t r iː m z /) are mammals of the order Monotremata. They are the only group of living mammals that lay eggs, rather than bearing live young. The extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified by structural differences in their brains, jaws, digestive tract ...
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 ...
Oviparity is found in insects, birds. Among mammals, the monotremes are oviparous. Ovo-viviparity: or oviparity with retention of zygotes in either the female's or in the male's body, but there are no trophic interactions between zygote and parents. [1] This mode is found in the slowworm, Anguis fragilis. In the sea horse, zygotes are retained ...
Monotremes, only five species of which exist, all from Australia and New Guinea, are mammals that lay eggs. They have one opening for excretion and reproduction called the cloaca . They hold the eggs internally for several weeks, providing nutrients, and then lay them and cover them like birds .
Oviparous reproduction in monotremes may give them an advantage over marsupials in some environments. [4] Their observed adaptive radiation contradicts the assumption that monotremes are frozen in morphological and molecular evolution.
The class Mammalia is divided into two subclasses based on reproductive techniques: egg-laying mammals (yinotherians or monotremes - see also Australosphenida), and mammals which give live birth . The latter subclass is divided into two infraclasses: pouched mammals ( metatherians or marsupials ), and placental mammals ( eutherians , for which ...
Oviparity is where fertilisation occurs internally and so the eggs laid by the female are zygotes (or newly developing embryos), often with important outer tissues added (for example, in a chicken egg, no part outside of the yolk originates with the zygote). Oviparity is typical of birds, reptiles, some cartilaginous fish and most arthropods.
Oviparity, as in most invertebrates and reptiles, monotremes, dinosaurs and all birds which lay eggs that continue to develop after being laid, and hatch later. [19] Viviparity, as in almost all mammals (such as whales, kangaroos and humans) which bear their young live. The developing young spend proportionately more time within the female's ...