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Across 1. Have no legs, no eyelids, no external ears and usually only one lung. 3. Reptile whose body is covered by a protective shell that includes the ribs and the backbone. 8. Pumps blood out to the lungs and body. 9. An animal whose body temperature changes depending on the temperature of its environment. 12. The larva of a frog. 13. You had some when you were an embryo, but not any more! 15. Chambers of the heart. 16. A fish's heart has ____ ____. 19. Has a shell, and internal membranes that help keep an embryo moist and allow it to carry out life functions. 22. Amphibians will return to this to reproduce. 26. An ectotherm that has fins and lives in water. 27. Most fish fall into this category. 29. Frogs and other amphibians are one of these. 30. Watery fluid excreted from the kidneys that helps an animal conserve water. 31. Each vertebra has one in it to allow for your spinal cord. 34. Most fish carry out ____ fertilization. 35. Sometimes ectotherms are referred to as this. 36. An animal that at some time in their lives will have a notochord, a nerve cord and gill slits. 37. They have four legs, usually claws on their toes, external ears, movable eyelids and two lungs. 38. The legs of frogs and toads have become adapted for this. 39. Amphibians also exchange oxygen and carbon dioxide through this.

Down 2. Organ that filters waste from the blood. 4. An ectothermic vertebrate that has scaly skin and lungs. 5. The earliest vertebrate that had legs positioned directly beneath its body. 6. The bones that make up your backbone. 7. What the word "amphibian" means. 10. Allows bony fish to stay stable at different depths in the water. 11. Native to Louisiana, it is the largest living reptile. 14. There are only two species of them left on Earth. 17. Acts as protection for amphibians and also helps them sneak up on their prey. 18. Animal whose body regulates its own temperature by controlling the internal heat it produces. 20. Sharks, rays and skates are this kind of fish. 21. All snakes are _____. 23. Ectothermic vertebrate that begins life in the water and spends adulthood on land. 24. Internal skeleton made of bone and/or cartilage. 25. Allows a fish to obtain oxygen from the water. 28. The world's longest venomous snake. 32. The specific environment in which an animal lives. 33. Most scientists think they are a direct descendant of the dinosaurs.