Difference Between Internal and External Fertilization

The life process of initiating the development of a new entity of its kind through the fusion of male and female gametes is known as fertilisation. The sperm from the male and the egg from the female unite, forming the zygote, a structure containing crucial genetic information from the mother and father individually. This article focuses on the differences between internal and external fertilisation.

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What Is Internal Fertilisation?

  • Syngamy of gametes occurs inside the female body after insemination through copulation.
  • Observed in birds, mammals, birds occurring in terrestrial plants and animals, and also in some of the aquatic entities. This is observed in three ways – ovoviviparity (eggs retained in the female body, hatched when fully developed, oviparity(egg-laying), and viviparity (offsprings develop within the female body).
  • Observes in plants such as bryophytes and pteridophytes.

What Is External Fertilisation?

  • Syngamy of gametes outside the female body/outer environment, notably in water bodies.
  • Observed in a few vertebrates, sea urchins, fish, aquatic invertebrates, and almost all amphibians.
  • Deposition of sperms and eggs by males and females in open surroundings is known as spawning.
  • Broadcast fertilisation – used when sperms swim through the water uniting with eggs to fertilise.

Difference Between Internal and External Fertilisation

Listed below are some significant differences between internal and external fertilisation:

Internal Fertilisation External Fertilisation
What is means
Fusion of gametes within the body of the female. Union of the gametes in an external environment(Water bodies).
Quantity of gametes released
Lesser is released and deposited inside the female’s body. Multiple gametes(both male and female) are released into the external environment.
Gametes involved
Only male gametes are discharged into the female genital tract. Both female and male gametes are discharged into the external surroundings.
Site of further development
Inside the female body. Outside the body.
  • Viviparity
  • Oviparity
  • Ovoviviparity
No types as such.
  • High survival chances as nourished by a parent.
  • Successful fertilisation rate is high.
  • Chances of success of survival in harsh conditions are high.
  • Offsprings produced are many.
  • Finding a mate requires less energy.
  • Competition between parents and their offspring is less.
  • Finding a mate requires much energy.
  • Most of the contribution is from the female counterpart.
  • Few offspring produced.
  • As they get preyed upon easily and, lack of parental care results in lesser survival chances.
  • Most of offspring go unfertilised, failing to survive until maturity.
  • Survival restricted to moist and wet environment only.
Reptiles, Birds, Mammals, Tracheophytes, Pteridophytes Algae, Fish, Amphibians

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