Reproduction in Animals - Revision Notes

CBSE Class 08 Science 
Revision Notes
Chapter – 9
Reproduction in Animals

Reproduction is a process in which the organisms produce the young ones of their own kind.

• There are two modes by which animals reproduce. These are: (i) Sexual reproduction, and (ii) Asexual reproduction
  
  Sexual Reproduction
   
• Reproduction resulting from the fusion of male and  female gametes is called sexual reproduction.
• The reproductive organs in the female include ovaries, oviducts and uterus.
• The reproductive organs in male include testes, sperm ducts and penis.
• The ovary produces female gametes called ova and the testes produce male gametes called sperms.
• The fusion of ovum and sperm is called fertilization. The fertilized egg is called a zygote.
• Fertilization that takes place inside the female body is called internal fertilization. This is observed in human beings and other animals such as hens, cows and dogs.
• Fertilization that takes place outside the female body is called external fertilization. This is observed in frogs, fish, starfish, etc.
• The zygote divides repeatedly to give rise to an embryo.
• The embryo gets embedded in the wall of the uterus for further development.
• The stage of the embryo in which all the body parts are identifiable is called foetus.
• Animals such as human beings, cows and dogs which give birth to young ones are called viviparous animals.
• Oviparous Animals: Animals that lay eggs are called oviparous animals, e.g., frogs, lizards, butterflies, etc.
• The transformation of the larva into adult through drastic changes is called metamorphosis.

Asexual Reproduction

• The type of reproduction in which only a single parent is involved is called asexual reproduction.
• In hydra, new individuals develop from buds. This method of asexual reproduction is called budding.
• Amoeba reproduces by dividing itself into two. This type of asexual reproduction is called binary fission.