Oviparity

Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, reptiles, all birds, and the monotremes. Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, reptiles, all birds, and the monotremes. In traditional usage, most insects, molluscs, and arachnids are also described as oviparous. The traditional modes of reproduction include oviparity, taken to be the ancestral condition, traditionally where either unfertilised oocytes or fertilised eggs are spawned, and viviparity traditionally including any mechanism where young are born live, or where the development of the young is supported by either parent in or on any part of their body. However, the biologist Thierry Lodé recently divided the traditional category of oviparous reproduction into two modes that he named ovuliparity and (true) oviparity respectively. He distinguished the two on the basis of the relationship between the zygote (fertilised egg) and the parents : In all but special cases of both ovuliparity and oviparity the overwhelming source of nourishment for the embryo is the yolk material deposited in the egg by the reproductive system of the mother (the vitellogenesis); offspring that depend on yolk in this manner are said to be lecithotrophic (opposed to matrotrophic), which literally means 'feeding on yolk'.