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Across 1. Birds have ______ which have a huge surface to weight ratio. 3. Amphibians have a_____chambered heart. 6. The nerve cord of chordates is________. 9. Reptiles are______. They bask in sun to keep warm. 10. Amphibians are the first to have a pressure releasing canal called the______tube. 12. This is a mammal group. The only living ______ are the duck-billed platypus and the spiny anteater. 15. Made their first appearance in fossils dating back approximately_______years ago. 18. Fish are mostly_____. 20. Birds have an outer covering of _____. 21. Reptiles have _____, very small plates covering their entire bodies. They prevent water from soaking into the reptile. 23. Reptiles are _____blooded. 24. _______larvae have a notochord and a nerve cord but these are lost in adulthood 25. This reptile order includes crocodiles, gharials, caimans and alligators. 28. Mammals have ______ or fur. 29. Located in the pharnyx and may form functional openings for gills or may appear only as groozes during an early stage of development. 31. Mammals brain regulates endothermic and ______ systems. 34. A birds _____ tract is very short, so that it can extract all the nutrients it requires and expel it quickly to not have to carry waste around with it. 37. Their offspring develop through a process called____. 39. Most are covered in_____while some can be covered in skin. 40. Birds have _____ red blood cells

Down 2. This reptile order includes lizards, snakes and amphisbaenids. 3. Birds have beaks or bills, and do not have _____. 4. Amphibians are______. 5. This is a mammal group. ______ give live birth very early after fertilization.Kangaroos, wallabies, and koala bears belong to this group. 7. Over 97% of all known fish are_______. The eggs develop outside the mother's body. 8. All fish are______. 11. The salamanders are part of the amphibian order ______. 13. Stiff but flexible rod located between the digestive tract and the nerve cord, that extends along the length of the body. 14. Vertebrate fish with jaws are in the class______. 16. Other animals lack this kind of tail. The posterior portion of a chordate body extends past the anus to form a _______. 17. Mammals are ______, which maintains a stable internal body temperature regardless of external influence 19. _______have a notochord and a nerve cord but no vertebrae 22. Reptiles are _____ meaning their eggs are laid with a hard outer shell. 26. They have_____which they use to breathe by drawing out oxygen from the water around them. 27. Most living mammals are _______. Horses, mice, bats, dogs, whales, and humans belong to this group. 30. Jawless fish are in the class______. 32. The frogs and toads are part of the amphibian order _____. 33. The____is a sac that collects discharge from the large intestine, urinary bladder, and gonads before it is eliminated from the body. 35. Mammals have a _____ chambered heart. 36. Most amphibians contain____eye lids. 38. Birds are ______blooded.