Reproduction in Animals Class 8 Notes - Chapter 9

Reproduction is vital for the continuation of species. There are two modes of reproduction in animals, they are:

  • Sexual reproduction – A type of reproduction in which gametes are produced by the reproductory parts and fuses to form a zygote which later develops into a new individual
  • Asexual reproduction – Type of reproduction which involves only a single parent.

The male reproductive parts in humans are comprised of a penis, a pair of testes and two sperm ducts. Male gametes known as sperms are produced by the testes. While the female reproductive organs include the uterus, oviducts (fallopian tube) and ovaries. Female gametes known as ova are produced by the ovary. In class 8 science chapter 9, sexual reproduction and asexual reproduction in animals are discussed.

Sexual Reproduction

  • The fusion of an ovum and sperm is the first step in sexual reproduction. When sperms come in contact with an egg, one of the sperms fuse with the egg. This process of fusion of the sperm and the egg is known as fertilisation.
  • The nucleus of both ovum and sperm fuse together to form a single nucleus and this results in the formation of a fertilised egg known as a zygote.
  • The zygote divides repeatedly to give rise to a ball of cells. These cells begin to form groups that further develop into different tissues and organs of the body. The developing structure is termed an embryo.
  • The embryo gets attached to the uterus and gradually develops body parts such as head, legs and hands. The stage of the embryo where all the body parts can be identified is termed as a foetus.
  • When the development of the foetus is complete, a mother gives birth to the child.

Animals that give birth to young ones are called viviparous while the animals that lay eggs are known as oviparous.

Asexual Reproduction

  • Very small and microscopic animals like hydra and amoeba reproduce through asexual reproduction. In hydra, the bulges called buds are the developing new individuals. This type of asexual reproduction is called budding.
  • The reproduction process in amoeba begins with the division of the nucleus into two nuclei. This is followed by the division of its body into two parts each obtaining a nucleus. This way, two amoebas are produced by a single parent. This type of reproduction where an animal divides into two is known as binary fission.

Reproduction in Animals Class 8 Extra Questions

  1. Describe the process of fertilisation in human beings.
  2. Mention two differences between a zygote and foetus
  3. Which female organ embeds the foetus?

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