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The egg cell is generally asymmetric, having an animal pole (future ectoderm). It is covered with protective envelopes, with different layers. The first envelope – the one in contact with the membrane of the egg – is made of glycoproteins and is known as the vitelline membrane (zona pellucida in mammals).
Goat kids will stay with their mother until they are weaned. Most mammals are viviparous, giving birth to live young. [1] However, the five species of monotreme, the platypuses and the echidnas, lay eggs. The monotremes have a sex determination system different from that of most other mammals. [2]
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.
Egg incubation is the process by which an egg, of oviparous (egg-laying) animals, develops an embryo within the egg, after the egg's formation and ovipositional release. Egg incubation is done under favorable environmental conditions, possibly by brooding and hatching the egg.
Ovipositor of long-horned grasshopper (the two cerci are also visible). The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs.In insects, an ovipositor consists of a maximum of three pairs of appendages.
Chickens that are "pasture-raised" or "free range" will typically lay eggs with a darker, more orange-colored yolk, Steele said, "because their diet consists mainly of grasses, weeds and other ...
Monotremes, egg-laying mammals, lay soft-shelled eggs similar to those of reptiles. The shell is deposited on the egg in layers within the uterus. The egg can take up fluids and grow in size during this process, and the final, most rigid layer is not added until the egg is full-size. [citation needed]
Cobras use leaves and other debris to build nests in which they lay eggs that both sexes guard. They carry the vegetation to the nest site by kinking their necks. [3] Sea turtles dig a hole in the sand above the high tide line in which they lay their eggs. They then cover the soft eggs to protect them from the sun and predators and leave. [1]