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Across 1. primary tissue layer that forms the gut and glands and respiratory system 8. organs that assist in minimizing water loss 9. hard external supporting structure 10. system that allows animals to sense their environment and to respond 12. primary tissue layer that will form the outer layer of the body (skin) and sense organs 13. system that provides support for animals 14. traits that set one group of animals apart from its ancestors and other groups that came from the same ancestor 17. type of skeleton that is a water filled cavity under pressure 20. animal cells lack this feature that allows them to be mobile 22. internal support structure made of bone or cartilage 23. system that extracts energy and nutrients from food 27. system not need to live, just to carry on the species 28. system that removes wastes 29. link between birds and dinosaurs 30. fish with jaws and large heads covered with bony plates 32. a digestive cavity with one opening 36. extinct order of mammal-like reptiles that gave rise to mammals 37. system that allows exchange of oxygen and carbon dioxide with the environment 39. early mammals were similar to these common day small mammals 45. gland that the pharyngeal pouches will become in vertebrates 46. ability to move 47. strong, flexible, lightweight material that composes some skeletons 50. trait shared by organisms with a common ancestor 51. group of fish with strong jaws 52. animal type that does not show segments

Down 2. one of the characteristics that all chordates share that will become the backbone 3. type of circulatory system in which heart pumps fluid to a cavity 4. primary tissue layer that forms the skeleton, muscles, circulatory system 5. how a body can be divided into similar pieces 6. cluster of nerve cells, similar to a brain 7. evolutionary adaptation that allowed for greater mobility and flexibility 11. simple arrangement of nerves, not efficient 15. fertilized egg 16. sponges digest their food within these structures 18. most primitive animal 19. group of dinosaurs that were plant eaters 21. animals that do not have a backbone 24. animals with a backbone 25. cells take on special shapes and functions 26. sponges and coral get their food this way because they can't food 31. unable to move 33. earliest fish without a backbone 34. the concentration of nerve tissue and sense organs at the anterior end of the body 35. system that transports gases, nutrients, and wastes within the body 38. the dorsal nerve cord will become this structure 40. type of circulatory system in which blood stays in blood vessels 41. the ability of early fish to be able to do what has a huge advantage to them 42. body cavity that contains the organs, fluid filled space 43. group of dinosaurs that were carnivores 44. animal's shape, symmetry, and internal organization 48. structure that the terrestrial organism use to take in oxygen 49. structure that the aquatic organisms use to take in oxygen