Animals: Asexual and Sexual Reproduction

Vivipary

A viviparous animal is an animal where the embryo develops inside the body of the mother, as opposed to outside in an egg. The mother then gives live birth.

Metamorphosis

is a biological process by which an animal physically develops after birth or hatching, involving a big change in the animal's form or structure through cell growth and differentiation.

Fragmentation

is a form of asexual reproduction where an organism is split into fragments. Each of these fragments develop into mature, fully grown individuals that are a clone of the original organism. It is seen in some annelid worms and starfish).

Budding

is the formation of a new organism by the protrusion of part of another organism. This may be found in animal organisms such as the hydra.

External fertilization

occurs in some animals living in water, like fish or amphibians. The female releases a large amount of ova and the male releases the sperm cells. Sperm cells join ova by chance.

REPRODUCTIVE ORGANS (GONADS)

- Gonads produce gametes (cells that fuse with another gamete during fertilization) - The gonads in males are the testes (sing. testis) and the gonads in females are the ovaries. - Testes produce sperm cells (small and motile) - Ovaries produce ova (sing. ovum) (large and non-motile)

Binary fission

An unicellular organism divides into two cells of the same size. It is used by most prokaryotes. The result is a living cell produced by division into two equal or near-equal parts

Oviparity

Oviparous lay eggs, with little or no other embryonic development within the mother.

Ovoviviparity.

Ovoviviparous animals develop within eggs that remain within the mother's body up until they hatch or are about to hatch.

Internal fertilization

The male introduce sperm cells in the female's body. It occurs in terrestrial animals, sharks and rays.

Gestation

called pregnancy in humans, is the period of time during which the fetus develops, dividing via mitosis inside the female.

Asexual

involves only one parent that produces two or more genetically similar organisms. It occurs mainly in organisms with a simple structure.

Polyembryony

is the only form of asexual reproduction in vertebrates. An embryo is divided in several identical embryos that have independent development (identical twins)

Sexual

reproduction involves two parents. A male sex cell joins with a female sex cell (fertilization) and they form a new cell called a zygote. The zygote grows into a new organism

development

the process by which an animal grows to reach their adult size