Across
- 2. found in all chordate embryos, turns into gills or respiratory systems
- 4. appendages extend from the central body, arm or leg
- 5. internal skeleton similar to vertebrates
- 6. body with two similar halves
- 10. earliest stage of development
- 12. protein that surrounds cells
- 13. combination of two or more tissues
- 14. any animal with a skull and backbone
- 16. hard outer coverings for protection
- 17. protection, reduce friction
- 18. support, turns into vertebrae
- 20. fanlike structures for movement, steering and balance
- 21. organs that remove oxygen from water
Down
- 1. a period of inactivity and decreased body temperature during the winter
- 3. spinal chord filled with spinal fluid
- 7. animals with no backbone
- 8. reduced activity in the summer
- 9. body parts are arranged in a circle around a central point
- 11. no backbone or developed head
- 15. " "
- 19. collection of similar cells