Most common frogs live in or around freshwater and lay their eggs in water. The eggs hatch into small tadpoles which grow and develop into frogs over a period of months. This change from tadpole to frog is called metamorphosis. The process involves not only the growth of legs, arms and loss of the tail, but internal gills are replaced by lungs and the digestive system changes to cope with a diet of insects rather than algae and decaying animal matter. The aquatic tadpole metamorphoses to become a land-dwelling frog.
Frogs are able to survive away from water, but not for long. Their thin, permeable skin is not waterproof, which means they can lose a lot of body water on warm days. For this reason, frogs are most active at night when they will hop about in search of food or a mate. During the day, they find a hiding spot and wait until the heat and light of the sun has passed.
Each frog species makes it own peculiar sound, but it is the male frog that does all of the calling to attract the females. If the female frog is also ready to breed, she will approach the male frog, he will climb onto her back (this embrace is called amplexus) and she will carry him to the egg-laying site. As she releases her eggs, the male frogs releases sperm over the eggs. Fertilisation occurs outside of her body, usually in pond water. The fertilised eggs develop and hatch to produce tiny tadpoles.