Question

Differentiate between internal fertilization and external fertilization.

Answer 1

Hint: The most advanced form of reproduction involves the fusion of the male gamete I.e. the sperm and the female gamete I.e. the ovum/ egg cell. A part of the sperm penetrates the ovum membrane ultimately fertilizing the egg cell.

Complete answer: Internal fertilization is the process when the syngamy (union of male and female gamete) occurs inside the female body after insemination using copulation. In contrast, External fertilization is the syngamy outside the female body, that is in the outer environment especially in water bodies.
The differences in external and internal fertilization are summarized here in the table given below:

EXTERNAL FERTILIZATION	INTERNAL FERTILIZATION
Takes place outside the female’s body.	Takes place inside the female’s body.
Usually, a large number of gametes are released in the surrounding medium (for example water).	Male gametes are released inside the body of the female by a copulatory organ.
Organisms that use external fertilization to reproduce must either live in the water or return to the water for reproduction.	Animals that have internal fertilization have completely transitioned to life on land.
As the chance of fertilization in water is generally less, hence, a large number of gametes are released.	The number of gametes produced in this mode is relatively less.
Examples: Fish, Amphibians, and most of the Algae, etc.	Examples: Reptiles, Birds, Mammals, Bryophytes, and Tracheophytes.

Note: The process of fertilization helps in restoring the total number of chromosomes present in any organism and this allows in maintaining the stability of genetic makeup throughout generations.