The offspring of animals are vulnerable to predators.

is the vital link that ensures continuity between one generation to the next.

 results in the formation of zygote.

Earthworms and sponges are animals.

 In oviparous animals like reptiles and birds, the fertilised egg is covered by a shell and laid in a safe place.

are the motile microscopic structures produced by many algal species.

Development of unfertilised ovum into a new individual is called .