Arthropods

Arthropods make up over 75% of the world's animal species. Arthropods include animals such as insects, crustaceans, and arachnids. The largest group of Arthropods is the insects. The next largest group is the crustaceans, including lobsters and crabs. The arachnids include spiders and ticks.

Other Arthropods include centipedes and millipedes.

Arthropods have limbs with joints that allow them to move. They also have an exoskeleton, a hard, external skeleton. The body cavity contains the nervous system, the circulatory system, the reproductive system, and the digestive system.