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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.
[89] [77] She lays one to three (usually two) small, leathery eggs (similar to those of reptiles), about 11 mm (7 ⁄ 16 in) in diameter and slightly rounder than bird eggs. [90] The eggs develop in utero for about 28 days, with only about 10 days of external incubation (in contrast to a chicken egg, which spends about one day in tract and 21 ...
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, reproductive tract, and other body parts, compared to the more common mammalian types.
A female python will not leave the eggs, except to occasionally bask in the sun or drink water. She will even “shiver” to generate heat to incubate the eggs. Some cichlid fish lay their eggs in the open, on rocks, leaves, or logs. Male and female parents usually engage in differing brooding roles.
It may occur in other situations. For example, female eiders prefer to lay eggs in the nests with one or two existing eggs of others because the first egg is the most vulnerable to predators. The presence of others' eggs reduces the probability that a predator will attack her egg when a female leaves the nest after laying the first egg. [23]
A nest is a structure built for certain animals to hold eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of organic material such as twigs, grass, and leaves, or may be a simple depression in the ground, or a hole in a rock ...
Cuckoos have various strategies for getting their eggs into host nests. Different species use different strategies based on host defensive strategies. Female cuckoos have secretive and fast laying behaviors, but in some cases, males have been shown to lure host adults away from their nests so that the females can lay their eggs in the nest. [31]
Bird nests are vulnerable to egg predation, especially for those such as eider ducks which nest on the ground. In response to the robbing of eggs from eider duck nests, half the individuals started a fresh clutch of eggs in a new nest; they always avoided the area around the robbed nest. [4]