What does an egg yolk contain that gives energy to embryo?

Animals need to reproduce to

In the above diagram of life cycle of a butterfly, in which stage does the organism cover itself in a cocoon?

The white part in the egg is called

The animals which suckle their young ones is called

In the egg stage of an organism, energy is obtained from

The eggs of fish are called

The following are the names of organisms and names of their "babies". Which one of them is NOT true?

A student observed that birds sit on their eggs before the eggs are hatched into young ones. The reason is

The animals live both on land and in water are called amphibians. Frog is such an animal. Now, where do frogs lay their eggs?