What animal lays the smallest egg?
The bee humming bird lays the smallest egg at half a gram, and the ostrich lays the biggest at 3.3lbs.
The animal that lays the smallest eggs are insects but when referring to vertebrates the animal that lays the smallest egg is the hummingbird.
How does the animal hatched out of the largest egg compare in size to the animal hatched out of the smallest egg at birth and later when fully grown?
The reason behind this depends on what animal your looking at. If the animal only lays one or two eggs, it has to be good enough parent to look after them. If it lays multiple eggs, like a frog, it lays these because many will be eaten and the chances of a frog egg becoming an adult frog is slim, only about 5 of the 200 eggs the female lays will make it adult life.