| A | B |
|---|
| invertebrate | an animal that does not have a backbone |
| ganglion | a mass of nerve cells |
| gut | the digestive tract |
| coelom | a body cavity that contains eht internal organs |
| bilateral symmetry | the two sides of an animals body mirror each other. |
| radial symmetry | an animals body is organized around the center, like spokes on a wheel |
| asymmetrical | you cannot draw a straight line to divide an animals body into two or more equal parts |
| cnidarians | a group of invertebrates that have stinging cells |
| parasite | an organism that invades and feeds on the body of another living organism that is callled a host |
| open circulatory system | a circulatory system in which the circulatory fluid is not contained entirely within vessels |
| closed circulatory system | a circulatory system in which the heart circulates blood through a network of blood vessels that form a closed loop |
| segment | an identical, or almost identical, repeating body part |
| exoskeleton | a hard, external, supporting structure |
| compound eye | an eye composed of many light detectors |
| antenna | a feeler that is on the head of an invertebrate that senses touch, taste, or smell |
| metamorphosis | a phase in the life cycle of many animals during which a rapid change from the immature form of an organism to the adult form takes place. |
| molting | a process in which nymphs shed their exoskeleton several times. |
| endoskeleton | an internal skeleton made of bone or cartilage |
| water vascular system | a system of canals filled with a watery fluid that circulates throughout the body of an echinoderm |
