Question

Differentiate between internal fertilisation and external fertilisation.

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Answer 1

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Fertilization, in general, is defined as the fusion of a male and a female gamete.

Internal fertilization

• It occurs inside the female body.
• There are high chances of survival of the offspring.
• Internal fertilization protects the fertilized egg or embryo from harsh environments.
• Examples are cow, humans, dogs, monkeys etc.

External fertilization

• It occurs outside the female body.
• There are low chances of survival of the offspring.
• Most aquatic animals use this type of fertilization and the advantage of external fertilization is that it
• produces a large number of offspring due to external hazards.
• Examples are fish, frog, organisms etc.

Answer 2

Answer:

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Internal Fertilization

• Syngamy of gametes occurs inside the female body after insemination through copulation
• Observed in birds, mammals, birds occurring in terrestrial plants and animals, 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), viviparity(offsprings develop within the female body)
• Observes in plants such as bryophytes, pteridophytes

External Fertilization

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