Egg layer

Oviparous animals lay eggs, inside which the young then develop before hatching occurs. Birds, reptiles, amphibians, fish, invertebrates and even some mammals (the monotremes) all lay eggs but they're of very different size and construction. The patterns on bird eggs are produced by glands right at the last moment as the egg is laid. For terrestrial species that lay their eggs on land, a waterproof shell prevents the contents from drying out.

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Species with this adaptation

Amphibians

Birds

Cartilaginous fishes

Heart urchins, sand dollars and sea urchins

Insects

Mammals

Octopus, Squid and allies

Polychaete

Ray-finned fishes

Reptiles

Sea stars and starfishes

About

Oviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, reptiles, all birds, the monotremes, and most insects and arachnids.

Land-dwelling animals that lay eggs, often protected by a shell, such as reptiles and insects, do so after having completed the process of internal fertilization. Water-dwelling animals, such as fish and amphibians, lay their eggs before fertilization, and the male lays its sperm on top of the newly laid eggs in a process called external fertilization.

Almost all non-oviparous fish, amphibians and reptiles are ovoviviparous, i.e. the eggs are hatched inside the mother's body (or, in case of the sea horse inside the father's). The true opposite of oviparity is placental viviparity, employed by almost all mammals (the exceptions being marsupials and monotremes).

There are only two known oviparous mammals: the Echidna and the Platypus, both native to Australia.

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