Question

Why does fish and frog lay egg in hundreds whereas a hen lays only one egg at a time

Answer 1

Frogs and fish mostly lay their eggs in water,larvae produced by them could flow along with water so to protect their generation they have to lay thousands of eggs at a time while hens lay eggs on land,so they do not need to lay many eggs.

Answer 2

Fish and frog show external fertilization and dog shows internal fertilization. In external fertilization there is a threat to predator,so very less sperm becomes an individual.