Question

Why frogs give out hundreds of eggs while hen lays only one egg

Answer 1

They use different tactics to ensure the best survival rates. In the case of fish, because most fish do not brood (protect their eggs), it makes sense to lay hundreds together so that at least a few may avoid predation. In the case of chickens, which do brood, it makes more sense to lay them only a few at a time and protect them until they hatch.

Among fish which do brood, it takes a long time to protect their eggs and this is time they can not spend searching for food in order to produce more eggs. Brooding fish also typically lay fewer eggs than fish which scatter them by the hundreds.

Chickens on the other hand are bound by evolution to protect their eggs or they will not hatch, since chickens are endothermic and their eggs require warmth in order to survive. Scattering eggs is not an option for them because evolution has locked them into a warm-blooded body plan.

Answer 2

The frogs are very delicate.the female fish and frog lays hundreds of eggs in water because as the animals like frog and fish undergo external fertilization,lay hundreds of eggs,all the eggs do not get fertilized and hence so no develop into new frog.this is because of many reasons: 1.frog lay the eggs and release sperms in water.many eggs and sperms are carried away by the movement of water,wind or rainfall,and hence all eggs do not get fertilized.
2.many of eggs of frogs are eaten up by other animals which live in water.
3.many larvae or young ones of frog and fish which are hatched from fertilized eggs are also eaten up by other animals and they fail to develop into adult frogs.