Question

Give details of two different ways in which a zygote develops in case of animals where fertilization is internal.

Answer 1

The union of sperm with an egg cell at the time of sexual reproduction, in the female body is called internal fertilization. In some fishes, some birds, reptiles and mammals the introduction of sperm in the female reproductive tract takes place by copulation.

Complete answer:
There are two different ways by which the development of zygote takes place via internal fertilization.

Internal fertilization in earthworm- An earthworm is a hermaphrodite. Hermaphrodite is an organism that does not fertilize itself. In this type of fertilization, two earthworms will come in close contact with each other and then the exchange of sperms takes place. When the sperms are received from the other partner, the eggs will be fertilized internally. Thus, the development of zygote takes place.

Internal fertilization in humans- When the male and female gamete meets inside the body, the fertilization takes place in humans. This type of fertilization is internal. Along with that the successive stages of the development of zygote into an individual by differentiation and multiplication of cells also takes place in the female body.

Note: The modes of reproduction are broadly classified into oviparous, viviparous. All the birds, most reptiles, and dinosaurs lay eggs and hatch them to produce their young one. This is called oviparity. Almost all the mammals give birth directly to their young ones which is called viviparity.