LIFE SCIENCE

Detailed explanation-1: -In fishes and frogs, the eggs get exposed to water movement, wind and rainfall. The chance of fertilisation of the egg increases if a large number of sperms are released. However, in hens, the fertilisation is internal, with higher chances of fertilisation. Therefore, hens lay only one egg at a time.

Detailed explanation-2: -As the chance of fertilization is nature dependant i.e it depends on the movement of water for the sperm to come in contact with the egg. Thus the fish and frog produce a huge number of eggs each year to overcome the chance factor(sperm to come in contact with egg) and produce offsprings.