Class Amphibia.pptx

Class Amphibia

1. Animal Diversity: Vertebrates by Maryam R iasat AMPHIBIANS

2. Amphibians The word "amphibian" means two-lives, one in the water and one on land . They live the first part of their lives in the water and the last part on the land. When they hatch from their eggs, amphibians have gills so they can breathe in the water. They also have fins to help them swim, just like fish. Later , their bodies change, growing legs and lungs enabling them to live on the land.

3. General Characteristics Spends first stages of life in water as tadpoles Tadpoles are herbivorous while adults are carnivorous Have no nails or claws Minimal number of teeth Most have a tongue that is projectile and sticky They are ectotherms During extreme environmental conditions they either hibernate (winter) or aestivate (summer ) The skin is smooth and rough without any scales, but with glands that make it moist Contains mucous glands, poison glands and pigment cells (colored)

4. Respiration Cutaneous – Gas exchange occurs across moist skin Pulmonary – Gas exchange occurs in paired lungs (too small for all gas exchange) Gills – Larval forms Amphibians have moist skin that is smooth, thin, and without scales . They have many capillaries directly beneath the skin and in the lining of the mouth . This makes it possible for oxygen and carbon dioxide to be exchanged . Amphibians also have small, simple, sac-like lungs in the chest cavity for the exchange of oxygen and carbon dioxide.

5. Circulation Blood system Heart: 2 atriums and 1 ventricle In an amphibian’s three-chambered heart, one chamber receives oxygen-filled blood from the lungs and skin, and another chamber receives carbon dioxide-filled blood from the body tissues . Blood moves from both of these chambers to the third chamber, which pumps oxygen-filled blood to body tissues and carbon dioxide-filled blood back to the lungs.

6. N ervous system Central nervous system is well developed The brain occupies completely the cranial cavity The brain is divided into fore, mid and hind brains Brain continuous as spinal cord. 10 pairs of cranial nerves will arise

7. Muscular and sensory system Well developed brain attached to the dorsal nerve cord They contain a well developed muscular system. Sensory receptors located all over the skin Good vision since these animals are mainly vision feeders T hey use their sight to find and capture food.

8.  Digestive System Amphibians have complete digestive system Use mouth, stomach and small intestine for digestion Contain the first true tongue, mucous and gland secretions make the tip of the tongue sticky Frogs have a long sticky tongue that is usually folded backwards in their mouth Food is captured by a sticky tongue and taken into the mouth It is then swallowed and moves through the pharynx and elastic esophagus to the stomach Once in the stomach, gastric digestive juices are secreted by glands that line the stomach allows the food to move into the intestines The leftover waste is pushed into the cloaca

9. Reproduction Even though amphibians are adapted for life on land, they depend on water for reproduction Because their eggs do not have a protective waterproof shell, they can dry out easily, so amphibians must have water to reproduce External fertilization in moist environments Amphibian eggs are fertilized externally by the male. As the eggs come out of the female’s body, the male releases sperm over them In most species the female lays eggs in a pond or other body of water

10. Urodels Urodels are group of amphibians with tail This order includes s alamandars and newts The body is divisible into head, trunk and tail The fore limbs and hind limbs are equal and weak Skin is scaleless Teeth present on both the jaws Eyes are small and eyelids are present in some urodels

11. Anures Anures are group of amphibians without tail This order includes frogs and toads They can live in water and on land Body is short and broad with head and trunk The fore limbs are small, the hind limbs are long for leaping and swimming, feet are webbed Skin is scaleless Teeth are on upper jaw or absent They show a pair of eyes External fertilization

12. Gymnophions Gymnophions are group of amphibians without legs Burrowing or aquatic Internal fertilization The body is long and snake like The body is divisible into head and trunk Tail is absent On the head two eyes are present S kin is covered by scales Lungs are asymmetrical

13.   Ecological Importance They play an important role in nature as both predator and prey, sustaining the delicate balance of nature. They eat pest insects, benefiting successful agriculture around the world and minimizing the spread of disease, including malaria. Most adult amphibians are insect predators and are helpful in keeping some insect populations in check. The skin of amphibians has substances that protect them from some microbes and viruses, offering possible medical cures for a variety of human diseases, including AIDS. Poison frogs, also known as poison dart frogs or poison arrow frogs, produce a poison that can kill large animals . The toxin is secreted through their skin and can affect muscles and nerves of animals that come in contact with it.