30-3 Amphibians Slide 1 of 47

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2 What Is an Amphibian? What Is an Amphibian? An amphibian is a vertebrate that, with some exceptions: lives in water as a larva and on land as an adult breathes with lungs as an adult has moist skin that contains mucous glands lacks scales and claws 2 of 47

3 Amphibians Amphibian Characteristics Lungs Pelvic Girdle Leg Bones: The legs of a land vertebrate must be strong enough to hold its weight. Skin: The skin and the lining of the mouth cavity of many adult amphibians are thin and richly supplied with blood vessels. Watery mucus is secreted by glands in the skin. 3 of 47

4 Evolution of Amphibians In many adult amphibians, the internal surfaces of the lungs are richly supplied with blood vessels and folds that increase surface area. Lungs 4 of 47

5 The class Amphibia is relatively small and diverse. 5 of 47

6 Feeding Tadpoles are typically filter feeders or herbivores that graze on algae. Their intestines help break down hard-to-digest plant material and are usually filled with food. The feeding apparatus and digestive tract of adults are meat-eating structures. 6 of 47

7 Frog Anatomy 7 of 47

8 Adult amphibians are almost entirely carnivorous. Many salamanders and frogs have long, sticky tongues specialized to capture insects. 8 of 47

9 In a frog s digestive system, food slides down the esophagus into the stomach. Mouth Esophagus Stomach 9 of 47

10 The breakdown of food begins in the stomach and continues in the small intestine. Small intestine Stomach 10 of 47

11 The liver, pancreas, and gallbladder secrete substances that aid in digestion. Gallbladder Liver Pancreas 11 of 47

12 At the end of the large intestine is a muscular cavity called the cloaca, through which digestive wastes, urine, and eggs or sperm leave the body. Large intestine (colon) Cloaca 12 of 47

13 Respiration In most larval amphibians, gas exchange occurs through the skin and the gills. Adult amphibians typically respire using lungs, but some gas exchange occurs through the skin and the lining of the mouth. 13 of 47

14 Circulation In frogs and other adult amphibians, the circulatory system forms a double loop. The first loop carries oxygen-poor blood from the heart to the lungs and skin, and takes oxygen-rich blood from the lungs and skin back to the heart. 14 of 47

15 The second loop transports oxygen-rich blood from the heart to the rest of the body, and carries oxygenpoor blood from the body back to the heart. 15 of 47

16 Amphibian Circulation and Excretion Heart Lung Kidney Ureter Urinary bladder Cloaca 16 of 47

17 The amphibian heart has three separate chambers: left atrium right atrium ventricle 17 of 47

18 Amphibian Heart From Body To body, lungs and skin To body, lungs and skin From Lungs Right atrium Left atrium Ventricle 18 of 47

19 Excretion Amphibians have kidneys that filter wastes from the blood. Urine travels through tubes called ureters into the cloaca. Urine is then passed directly to the outside, or temporarily stored in a small urinary bladder just above the cloaca. 19 of 47

20 Reproduction In most species of amphibians, the female lays eggs in water, then the male fertilizes them externally. In a few species, including most salamanders, eggs are fertilized internally. After fertilization, frog eggs are encased in a sticky, transparent jelly. 20 of 47

21 The jelly attaches the egg mass to underwater plants and makes the eggs difficult for predators to grasp. The yolks of the eggs nourish the embryos. Most amphibians abandon their eggs after they lay them. A few amphibians take care of both eggs and young. 21 of 47

22 Frog Metamorphosis Adult Frog Young Frog Fertilized eggs Tadpoles 22 of 47

23 Adults are typically ready to breed in about one to two years. Frog eggs are laid in water and undergo external fertilization. 23 of 47

24 The fertilized eggs hatch into tadpoles a few days to several weeks later. Fertilized eggs 24 of 47

25 Tadpoles gradually grow limbs, lose their tails and gills, and become meat-eaters as they develop into terrestrial adults. Young frog Tadpole 25 of 47

26 Movement Amphibian larvae move by wiggling their bodies and using a flattened tail for propulsion. Adult salamanders walk or run. Frogs and toads, have well-developed hind limbs that enable them to jump long distances. 26 of 47

27 Response Amphibians have well-developed nervous and sensory systems. An amphibian's eyes are protected from damage and kept moist by a transparent nictitating membrane. This membrane is located inside the regular eyelid and can be closed over the eye. 27 of 47

28 Amphibians hear through tympanic membranes, or eardrums, located on each side of the head. Many amphibian larvae and adults have lateral line systems that detect water movement. 28 of 47

29 Frog s Sense Organs 29 of 47

30 Groups of Amphibians Groups of Amphibians The three groups of amphibians are: salamanders frogs and toads caecilians 30 of 47

31 Groups of Amphibians Salamanders Salamanders and newts have long bodies and tails. Most have four legs. Both adults and larvae are carnivores. Adults usually live in moist woods, where they tunnel under rocks and rotting logs. 31 of 47

32 Groups of Amphibians Frogs and Toads Frogs and toads have the ability to jump. Frogs tend to have long legs and make lengthy jumps. Toads have relatively short legs and are limited to short hops. 32 of 47

33 Groups of Amphibians Frogs are generally more closely tied to water than toads. Toads often live in moist woods and even in deserts. 33 of 47

34 Groups of Amphibians Caecilians Caecilians are legless animals that live in water or burrow in moist soil or sediment. Caecilians feed on small invertebrates such as termites and resemble large worms. Many have fishlike scales embedded in their skin. 34 of 47