An egg gets fertilized when a sperm from the male is allowed through the egg membrane and mixes its chromosomes with those of the egg from the female. With many egg producing creatures in the oceans, rivers, and lakes, the males and females release their eggs and sperm at the same time and they make the water cloudy. Some amphibians release their eggs and sperm from the leaves of trees and they drop in the water together. Some animals use internal fertilization. With birds and reptiles, the eggs are fertilized inside the female before the hard shell forms. Other beings that fertilize their eggs internally give birth to live babies.