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Classification Amphibians • The Class Amphibia (or amphibians) includes three Orders: • Anura (frogs and toads) – about 5,800 species • Caudata or Urodela (newts and salamanders) – about 580 species • Gymnophiona or Apoda (caecilians) – about 170 species • Frogs and Toads Newts and Salamanders Caecilians How do frogs breathe? • Breathing is a gas exchange, taking in oxygen and letting out carbon dioxide. • All frogs start life as aquatic tadpoles, breathing underwater through internal gills and their skin. • Later they develop into land animals with lungs for breathing air. Most frogs loose their gills when they change from tadpoles to frogs. • Frogs breath with their mouths closed. Their throat movements pulls air through the nostrils to the lungs. Then breathe out with body contractions. • Frogs can also breath through their skin, with tiny blood vessels, capillaries, under the outer skin layers. Breathing through the skin • While completely submerged all of the frog's repiration takes place through the skin. • The skin is composed of thin tissue that is permeable to water and contains a large network of blood vessels. • The thin skin allows the respiratory gases to readily diffuse directly down between the blood vessels and the surroundings. • When the frog is out of the water, mucus glands in the skin keep the frog moist, which helps absorb dissolved oxygen from the air. Body temperature and behaviour of Amphibians • The body temperature of amphibians is determined by the environment. • In warmer surroundings amphibians have more energy and move faster. • In Autumn amphibians find a place to hibernate for the winter. • During hibernation the heart beat frequency, the gas exchange and respiration slows down. What do Amphibians eat? • Insects, larve, worms, spiders and snails. • Many amphibians have special techniques to catch their prey, e.g. the frog.