Marine Animals

4. A structure in the pregnant uterus for nourishing a viviparous fetus with the mother's blood supply
5. an organism must produce its own body heat
7. an animal without a backbone
10. one of two principal body types occurring in members of the invertebrate animal phylum Cnidaria
13. a thin-walled sac located inside the body of a fish that is usually filled with gas.
14. An air-breathing egg
15. an animal that has a spine
16. an organism instead relies on external environmental factors to regulate its body temperature,
18. a skeleton found within the interior of the body
20. the shedding and replacement of horns, hair, skin, and feathers.
21. The lack or absence of symmetry

1. tiny little animals that are related to anemones and jellyfish.
2. a hydraulic system used by echinoderms,
3. a single individual has both male and female reproductive organs
6. A tough, flexible tissue that lines joints and gives structure
8. an animal with no right or left sides, only a top or bottom
9. the form of an outgrowth form an organism
11. an external skeleton that supports and protects an animal's body
12. a body plan in which the body can be divided into mirror images along a central axis.
17. the lowest level of a body of water
19. milk-producing gland characteristic of all female mammals