NCERT Solutions Class 8th Science Chapter – 6 Reproduction in Animals Notes

There are two modes by which animals reproduce. These are

• Sexual reproduction and
• Asexual reproduction.

Male Reproductive Organs – Male reproductive organs are a pair of testes, sperm ducts, and a penis.

Sperms – The testes produce the male gametes called sperms.

Female Reproductive Organs – The female reproductive organs are a pair of ovaries, oviducts (fallopian tubes) and the uterus.

Ova – Ovary produces females gametes called ova (Egg).

• In human beings, a single matured egg is released into the oviduct by one of the ovaries every month.

• Uterus is the part of the female reproductive system where the development of the embryo takes place.
Both sperm and ova are single-celled structure.

• The fusion of the ovum and the sperm is called fertilisation.

• Fertilisation which takes place inside the female body is called internal fertilisation.

• Fertilisation which takes place outside the body of the female is called external fertilisation.

• During fertilisation, the nuclei of the sperm (n) and the egg in) are fused to form a single nucleus (2n). This fertilised egg is called zygote.

• The zygote divides repeatedly to give rise to a ball (mass) of cells. The cells then begin to differentiate into various tissues. This developing structure is called an embryo.

(a) Zygote formation and development of an embryo from the zygote
(b) Ball of cells (enlarged)
(c) Embedding of the embryo in the uterus (enlarged)

• The embryo gets implanted within the wall of the uterus, i.e., endometrium for further development.

• The stage of the embryo in which all the body parts are identifiable is called a foetus.

• The animals which give birth to young ones are called viviparous animals.

• The animals which lay eggs are called oviparous animals.

• The transformation of larva into an adult through drastic changes is called metamorphosis.

• In small animals like a hydra, new individuals develop from buds. This method of asexual reproduction is called budding.

Bud – A lateral outgrowth from the parent body that assumes the shape of parent. It ultimately gets detached and behaves as a new individual.

• Amoeba a single-celled organism, reproduces by simply dividing itself into two daughter cells. This type of asexual reproduction is called Binary fission.