Frogs have existed for 190 million years. Over time, frogs have managed to adapt to live in ponds but also venture out of the water onto grasslands and into trees to survive. Their remarkable adaptability has enabled them to survive in fresh water around the world. The amphibious frog occurs on every continent of the world except Antarctica, according to the Exploratorium
Water and Food
The frog uses water as its refuge. It will dive beneath the water's surface to avoid possible predators. Frogs also eat a wide array of foods on land and in the water. A carnivore, the frog survives on insects, small fish and snails. Some large frogs will leave the water to hunt mice on land. The frog has evolved to have a long tongue. It whips its tongue out of its mouth at lightning speed to lasso its prey. Once the sticky tongue wraps around the frog's victim, the frog snakes its tongue back into its mouth to consume its entrapped meal.
The frog can survive freezing temperatures by burrowing into the mud of the pond. The frog's body can freeze for weeks and the frog will continue to survive. Glucose in the frog's blood congests around the amphibian's vital organs. The substance helps keep the organs warm while the frog's body solidly freezes. Some species of frogs, such as bullfrogs and green frogs, sit on the mud of the pond beneath the water's surface and do not cover their bodies. They often look dead beneath the water.
The feet of the frog have webs that allow the frog to swim with ease through the pond's water. On land, the frog can jump considerable distances using its powerful, well-muscled hind legs. It can leap up to 20 times its body's length. The webbed feet on a tree frog help the frog swim through the water and glide from tree branch to tree branch. The frog breathes through its skin on land and beneath the water. It also has nostrils and lungs that it utilises on land to gain adequate oxygen.
Frogs mate in the water, and the female lays her eggs on the water around aquatic plants. The eggs take from 6 to 21 days to hatch, depending on the frog species. Some frogs remain with the eggs. The tadpoles emerge from the eggs with gills and a tail. Upon hatching, the tadpole begins to swim in the pond water and feed on algae. At four weeks old, the tadpole loses its gills and begins to grow tiny teeth in its mouth. At six weeks, legs sprout from the tadpole's body. Between nine to 12 weeks the tadpole's tail disappears and it begins to look like a small frog. At 12 weeks of age, the tadpole can successfully leave the pond water. Most frog species reach full maturity at 12 to 16 weeks old.