Class 12 Biology Reproduction In Organisms Fertilization


The process of fusion of male and female gametes to form a zygote is called fertilization or syngamy.

Fig. fusion of sperm and egg

  • Fertilization is of two types-
  • In rotifers, insects, lizards female gametes develop in to new organisms without fertilization, the process is called as

External fertilization-

  • In this type of fertilization, syngamy occurs outside the body of organism. Example- in most aquatic organisms like algae, fish, amphibians.
  • The major disadvantage of external fertilization is they produce a large number of off springs but the off springsare vulnerable to predators.

Fig. external fertilization and release of eggs in water


Internal fertilization-

  • Syngamy occurs inside the body of organisms. Example- fungi, birds, mammals.
  • Male gametes are released close to the female gametes.

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