A frog is a vertebrate and cold-blooded amphibian belonging to the order Anura. There are about 4,800 described species of frogs. They vary in size, ranging from 7.7 mm to 300 mm. An adult frog is characterized by a short body, long hind legs, protruding eyes, and webbed digits. It has a soft, smooth skin, covered with moist slime, mucus. The skin is permeable, allowing the gas and liquid to pass through it. They are carnivorous and feed on a wide variety of prey such as spiders, worms, insects, crustaceans, and small reptiles.
A Detailed View
The life cycle of a frog starts in the water, in the form of eggs. A male frog gives a mating call to the female, usually during spring. When the male and female frogs are in the amplexus phase, the female lays the eggs in the water and the male externally fertilizes the eggs. Frogs, in most cases, lay eggs in clusters in lakes, ponds, or puddles. A mass of embryo is called frogspawn. About thousands of eggs are deposited at a time. These eggs are covered by a gelatinous fluid, so that they are protected from harm. Each egg sack contains about hundreds of eggs. Some of the eggs die or some are swallowed by the predators. Rest of them that survive develop into an embryo.
The embryos inside the jelly balls feed on the surrounding jelly and start to form the gills and other organs. The embryos are developed into the tadpoles. After completion of embryo's development period of 21 days, the egg breaks up and the tadpole emerges out. It starts to collect oxygen from the water using its external gills. It feeds on algae using its small peculiar mouth. The tadpole develops a long, compressed tail, which is used for swimming in the water.
Within a period of five weeks, the tadpole starts changing its anatomy. The external gills are replaced by a fold of skin, known as an operculum. The tadpole develops tiny teeth. Its mouth becomes broader and eyes become more prominent. After one week, the lungs are developed and the tadpole can breathe air. Later, the tadpole develops the front legs within 10 - 12 weeks. The froglet is then able to hop on the land. Once the forelegs are developed, the tadpole feeds on its tail. Its digestive tract changes to get ready for its forthcoming insect diet.
Within a period of three-and-a-half months, it is developed into a froglet and able to eat small bugs. It later loses its tail and the growth is complete; it is considered as an adult frog, then. Now, it is able to live in the water, as well as on the land. The transformation process can last from 12 days to 3 years, depending upon the specific species. Within a period of four years, this new frog starts breeding and its life cycle continues.