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Reproduction in Animals Notes for Class 8

Important topics covered:

  • Introduction
  • Modes of reproduction
  • Sexual reproduction
  • Male reproductive system
  • Female reproductive system
  • Fertilization
  • Development of embryo
  • Viviparous and Oviparous Animals
  • Zygote
  • Asexual reproduction


  • As life processes are essential to sustain life on this earth so is the reproduction.
  • Reproduction is responsible for the continuation of species on this earth.
  • It keeps the species existence generation by generation.
  • Both plants, as well as animals, carry out the process of reproduction.

Modes of reproduction:

There are two modes of reproduction:

  • Sexual reproduction
  • Asexual Reproduction

Similarities of reproduction between plants and animals:

similarities of reproduction in plants and animals

  • Both plants, as well as animals, undergo the sexual and asexual mode of reproduction.
  • Plants that reproduce sexually have different male and female reproductive parts like that in animals.
  • The zygote is formed by the fusion of male and female gametes in both the plants and animals, which develops into a new individual.

Sexual Reproduction:

  • The mode of reproduction which involves the fusion of male as well as female gametes to form zygotes is known to be sexual reproduction.
  • Male parents produce male parents.
  • Female parents produce female gametes.
  • Fusion of both gametes is the main step in sexual reproduction.

Male reproductive organ:

male reproductive system

  • The male reproductive organs consist of a pair of testes, two sperm ducts and a penis.
  • The testes produce the male gametes which are said to be sperms. These are produced in millions.
  • Sperm being very small though it consists of a head and tail.
  • Each sperm is a single cell with all the essential cell components.

Female reproductive organ:

female reproductive dystem

  • The female reproductive system consists of a pair of ovaries, a pair of oviducts (fallopian tubes) and a uterus, Vagina.
  • Pair of ovaries produce eggs (female gametes).
  • Every month an egg is released into
  • The development of the baby takes place at the uterus.
  • Similar to sperm, Egg also is single-celled and contain cytoplasm and nucleus.
  • In human beings, these eggs are very small. Egg of Ostrich is the largest.


fertilisation of egg

  • At first, the fusion of a sperm and an ovum takes place during reproduction.
  • The process of fusion of male and female gametes i.e. when single sperm fuse with the egg is said to be fertilisation.
  • Simply, fertilisation is the process of meeting of an egg cell from the mother and a sperm cell from the father.
  • The nuclei of the sperm and the egg fuse to form a single nucleus during fertilization.
  • Thus a fertilized egg or zygote is formed. This zygote develops into a new individual.
  • The new individual as a result of fertilisation inherits some characteristics from the mother and some from the father.

There are two types of fertilization:

  • Internal fertilization: Fertilisation which takes place inside the female body. This type of fertilization is observed in humans, dogs, cows and hens.

internal fertilisation

  • External fertilization: Fertilisation which takes place outside the body of organism. Toads and frogs move to ponds and slow-flowing streams during rainy season. Male and female come together in water where female lays hundreds of eggs and male deposits sperm over them and thus fertilization takes place.

external fertilisation

Development of Embryo:


  • Zygote is formed as a result of fertilization which begins to develop into an embryo.
  • Repeated division of zygote gives rise to ball of cells, these cells then constitute to tissues and then to organs of the child’s body. We call this developing structure as embryo.
  • For further development, embryo gets embedded in the wall of the uterus.
  • In uterus the embryo continues to develop into different body parts like hands, head, legs, eyes etc.
  • The stage of embryo when all the body parts can be identified is said to be foetus.
  • After the complete development of foetus mother gives birth to her baby.
  • In external fertilization, soon after fertilisation, the zygote travels down the oviduct. As it travels down, many protective layers are formed around it (egg of hen has hard covering).
  • Around the developing embryo when the hard shell is formed, the hen lays the egg. A sufficient warmth is provided to the eggs of hen. And after 3 weeks chicks are developed from eggs.
  • The embryos grow within their egg coverings.
  • Thus, reproduction in animals notes provide all the explanations.

Viviparous and Oviparous Animals:

  • The animals which give birth to young ones are called viviparous animals.
  • Dog, cat or cow are examples of viviparous animals.
  • Those animals which lay eggs are called oviparous animals.
  • Hen, crow, ostrich are some examples of viviparous and oviparous animals.

Young ones to adults:

young one to adults

  • The young ones which either took birth or hatched from eggs continue to grow into adults.
  • In some animals, we see that young ones look very different from the adults.
  • Lifecycle of silkworm:
  • Lifecycle of frog:
  • Metamorphosis: The transformation of the larva into an adult through drastic changes are known to be metamorphosis.

Asexual Reproduction:

  • The mode of reproduction in which only a single parent is involved is called asexual reproduction.
  • New individuals are formed from a single parents in this case.

Different Modes of Asexual Reproduction

In different organisms, there are different modes of asexual reproduction. They are:


budding in hydra

  • Budding is a case of asexual reproduction in the organism like hydra, which develops a bulge called bud.
  • This bud develops into an adult hydra-like structure.
  • The structure gets separated from the parent hydra leads independent life.

Binary fission:

binary fission of amoeba

  • This mode of asexual reproduction is observed in unicellular organisms.
  • Binary fission is seen in case of amoeba.
  • Nucleus of parent divides into two daughter nuclei.
  • Each daughter cells develops into new adults.
  • Paramecium and leishmania undergoes binary fission.


cloning in asexual reproduction

  • A process in which exact copy of the cell or any living part or a complete organism is produced is said to be cloning.
  • It is an artificial method discovered by man to produce organisms without sexual or asexual reproduction.

FAQ related to Reproduction in animals:

What are the differences between sperm and egg in human being?

The difference between sperm and egg cell are:

Sperm Cell Egg Cell
Egg is produced in ovaries. Sperm is produced in the testes.
It is spherical in shape with a nucleus. It has s head with nucleus, middle piece and tail.

Mention the changes which occur during adolescence in humans.

There are two main types of hormones which influence adolescent age in humans. They are  – sex hormones and growth hormones. The adolescent period shows rapid changes in the following things:

  • Physical, emotional, cognitive and social appearance.
  • Sex hormones in this age make the sex organs active and child reaches puberty.
  • Many physical changes in girls like breast development, growth of body hair, onset of menstruation, growth spurts occur.
  • In boys, growth of body hair, growth spurs, change in voice, muscle development etc. occur.
  • Teenagers become self-conscious in social circles.
  • Adolescence is also a very emotional time for teenagers. Hormones bring about mood changes and increased sexual urges.

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