The brain and spinal cord are part of the _______ nervous system. The electrical charges that act as nervous signals are called _______. Jellyfish do not have a brain. Instead their nervous system is called a _______. After nervous systems began to develop in bilaterally symmetric animals, some developed ventral, or front, nerve cords, while chordates developed _______ nerve cords. Skeletons that allow for movement by using muscles and squeezing liquid to change the body shape are called _______ skeletons. _______ do not grow with arthropods, and so occasionally must be shed and regrown from chitin. Muscles move endo- and exoskeletons by _______. _______ is the joining of two gametes called sperm and egg. A fish that lays her eggs in a cluster is initiating _______ fertilization. _______ are an adaptation by reptiles to allow for reproduction and embryo development on land. Describe three different strategies used by three different animals to thermoregulate. If you see a snake coiled up in a sunny patch of grass, what can you probably conclude about the type of thermoregulator it is. Why?
