Copyright Pearson Prentice Hall 30-3 Amphibians Photo Credit: Animals Animals/©Bill Beatty Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 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 Copyright Pearson Prentice Hall

Evolution of Amphibians The first amphibians appeared in the late Devonian Period, about 360 million years ago. The transition from water to land required that the terrestrial vertebrates had to: breathe air, protect themselves and their eggs from drying out, and support themselves against the pull of gravity. Copyright Pearson Prentice Hall

Evolution of Amphibians Early amphibians evolved several adaptations that helped them live at least part of their lives out of water. Bones in the limbs and limb girdles of amphibians became stronger, permitting more efficient movement. Copyright Pearson Prentice Hall

Evolution of Amphibians Lungs and breathing tubes enabled amphibians to breathe air. The sternum formed a bony shield to support and protect internal organs, especially the lungs. Copyright Pearson Prentice Hall

Evolution of Amphibians Amphibian Adaptations Lungs Pelvic Girdle Leg Bones: The legs of a land vertebrate must be strong enough to hold its weight. The characteristics of amphibians include adaptations for living partially on land. For example, lungs enable adult amphibians to obtain oxygen from air. 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. Copyright Pearson Prentice Hall

Form and Function in Amphibians The class Amphibia is relatively small and diverse. Copyright Pearson Prentice Hall

Form and Function in Amphibians Frog Anatomy This illustration shows the organs of a frog’s digestive system. Copyright Pearson Prentice Hall

Form and Function in Amphibians Mouth Esophagus In a frog’s digestive system, food slides down the esophagus into the stomach. Stomach This illustration shows the organs of a frog’s digestive system. Copyright Pearson Prentice Hall

Form and Function in Amphibians The breakdown of food begins in the stomach and continues in the small intestine. Stomach Small intestine This illustration shows the organs of a frog’s digestive system. Copyright Pearson Prentice Hall

Form and Function in Amphibians The liver, pancreas, and gallbladder secrete substances that aid in digestion. Gallbladder Liver Pancreas This illustration shows the organs of a frog’s digestive system. Copyright Pearson Prentice Hall

Form and Function in Amphibians 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 This illustration shows the organs of a frog’s digestive system. Copyright Pearson Prentice Hall

Form and Function in Amphibians 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. Copyright Pearson Prentice Hall

Form and Function in Amphibians Amphibian Circulation and Excretion Heart Lung Kidney Ureter Urinary bladder Cloaca Like all vertebrates, amphibians have a circulatory system and an excretory system. An amphibian’s heart has three chambers—two atria and one ventricle. Although some wastes diffuse across the skin, kidneys remove most wastes from the bloodstream. Copyright Pearson Prentice Hall

Form and Function in Amphibians Frog Metamorphosis Adult Frog Fertilized eggs Young Frog An amphibian typically begins its life in the water, then moves onto land as an adult. This diagram shows the process of metamorphosis in a frog. Tadpoles Copyright Pearson Prentice Hall

Form and Function in Amphibians Adults are typically ready to breed in about one to two years. Frog eggs are laid in water and undergo external fertilization. An amphibian typically begins its life in the water, then moves onto land as an adult. Copyright Pearson Prentice Hall

Form and Function in Amphibians Frog’s Sense Organs Photo Credit: Animals Animals/©Bill Beatty. A frog’s eyes and ears are among its most important sensory organs. Transparent eyelids called nictitating membranes protect the eyes underwater and keep them moist in air. Tympanic membranes receive sound vibrations from air as well as water. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Groups of Amphibians Groups of Amphibians The three groups of amphibians alive today are: salamanders frogs and toads caecilians Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 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. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 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. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 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. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 30-3 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 30-3 The word amphibian refers to the ability to live in hot climates. live in wet places. live both in water and on land. live in cold and hot climates. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 30-3 Fossil evidence indicates the first land amphibians appeared during the Jurassic Period. Devonian Period. Cambrian Era. Cretaceous Era. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 30-3 In a larval amphibian, gas exchange occurs through the skin only. both the skin and the gills. the gills only. in a lung. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 30-3 The tympanic membrane in a frog enables it to hear. see. smell. taste. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 30-3 Which of the following is a group of amphibians living on the Earth today? crocodiles snakes salamanders lizards Copyright Pearson Prentice Hall

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