| A | B |
|---|
| Phylum Arthropoda | invertebrates with jointed legs |
| Class Arachnida | spiders, scorpions, ticks |
| exoskelton | hard covering made of chitin |
| cephalothroax | head and chest fused into 1 segment |
| open circulatory system | blood not in vessels |
| book lungs | used for respiration in arachnids |
| molt | to shed the covering |
| carapace | exoskeleton covering the cephalothroax of a crayfish |
| body segmentation | the body of a typical arthropod is divided into 3 segments |
| heart | located dorsally |
| nervous system | located ventrally |
| compound eyes | contain thousands of individual lenses |
