1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu of Amphibians The first group of vertebrates to live on land were the amphibians, which appeared about million years ago. Amphibians probably evolved from a group of bony fishes called The pattern of in an amphibian’s limbs bears a strong resemblance to that of a lobe-finned fish. (Ichthyostega had 5 toes on hind feet) Vertebrates in the Sea and on Land

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Vertebrates in the Sea and on Land

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Evolution of Amphibians Adaptations for Life on Land A number of major adaptations allowed some species to successfully 1.. Legs support the body’s weight as well as allow movement from place to place. 2.. On land, lungs carry out gas exchange. 3.. Land animals tend to have higher metabolic rates than aquatic animals. The structure of the vertebrate heart allows oxygen to be delivered to the body efficiently. Vertebrates in the Sea and on Land

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Modern Amphibians All of today’s amphibians are descendants of the amphibians that survived into the They are found in aquatic and moist throughout the temperate and tropical regions of the world. make up the largest, and probably the most familiar, group of modern amphibians. Vertebrates in the Sea and on Land

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Key Characteristics of Modern Amphibians Most share five key characteristics: 1. 2. 3. Double-loop 4. Partially divided (pumping organ = ventricle) 5. Cutaneous Amphibians

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Key Characteristics of Modern Amphibians, continued Lungs A is an internal, baglike respiratory organ that allows oxygen and carbon dioxide to be exchanged between the air and the In, the lungs are hardly more than sacs with folds on their inner membrane that increase their area. Many amphibians also obtain through their thin, moist skin. Amphibians

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Amphibians LUNGS

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Key Characteristics of Modern Amphibians Double-Loop Circulation As amphibians evolved and became active on land, their circulatory system changed, resulting in a Amphibians have a pair of blood vessels not found in fishes, the pulmonary veins. The veins carry oxygen-rich blood from the amphibian’s lungs to its heart. The pumps the oxygen-rich blood to the rest of the body. Amphibians

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Key Characteristics of Modern Amphibians, continued Double-Loop Circulation in fishes involves a single loop. Amphibians have a second loop that goes from the heart to the lungs and Amphibians

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Key Characteristics of Modern Amphibians, Circulation of Blood A dividing wall known as the separates the amphibian atrium into right and left halves. The septum prevents the complete mixing of oxygen- rich and oxygen-poor as each enters the heart. A number of amphibians have a spiral valve that divides the conus arteriosus. The spiral valve also helps to keep the two streams of blood separate as they Pulmonary circuit carries deoxy. blood to Amphibians

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Amphibians

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Frogs and Toads The order is made up of frogs and toads that live in environments ranging from deserts to rain forests, valleys to mountains, and ponds to puddles. Adult anurans are carnivorous, eating a wide variety of small The frog body, particularly its, is adapted for jumping, and its long muscular legs provide the power. Amphibians

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu External Structure of a Frog—Leopard Frog Amphibians Membrane protects the eye. Tympanic Membrane senses vibrations – hears – columella transmits

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Amphibian Brain – regulates muscular coordination Medulla oblongata – controls heart & Cerebrum – integrates SOME PARTS: – middle part of small intes- tines. – membrane, holds small intestine in place. Kidney – filters nitrogen Amplexus – Mating embrace – Opening for wastes.

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Internal Structure of a Frog— Leopard Frog Amphibians have chambered hearts. Amphibians Cloaca Lung ➘ Brain

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Frogs and Toads, continued Reproduction in Frogs Like most living, frogs depend on the presence of water to complete their life cycle. The female releases her eggs into the water and a male’s sperm fertilize them After a few days, the fertilized eggs hatch into swimming, fishlike larval forms called tadpoles. Tadpoles develop into adult frogs through the process of metamorphosis (stimulated by ) Amphibians

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Amphibians

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Salamanders and Caecilians have elongated bodies, long tails, and smooth, moist skin. (order = Urodela) Salamanders lay their eggs in water or in moist places. is usually external. Unlike frog and toad larvae, salamander larvae do not undergo a dramatic The young that hatch from salamander eggs are carnivorous and resemble small versions of the adults, except that the young usually have Amphibians

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Salamanders and Caecilians, continued Caecilians Caecilians (order Apoda) are a highly specialized group of tropical, burrowing with small, bony scales embedded in their skin. During breeding, the male deposits directly into the female. Depending on the species, the female may bear live young or lay that develop externally. are rarely seen, and scientists do not know a lot about their behavior, but are wormlike with small eyes and often blind. Amphibians