Arthropods

The Arthropods, the largest animal phylum, includes insects, spiders, crustaceans, and Myriapoda (Millipedes and Centipedes). Arthropods range in distribution from the deep sea to mountain peaks, in size from the king crab with its 12-foot armspan to microscopic insects and crustaceans, and in taste from chocolate covered ants to crawfish jambalaya and lobster Newburg. Despite this unbelievable diversity, the basic body plan of arthropods is fairly constant. Arthropods have a stiff cuticle made largely of chitin and proteins, forming an exoskeleton that may or may not be further stiffened with calcium carbonate. They have segmented bodies and show various patterns of segment fusion (tagmosis) to form integrated units (heads, abdomens, and so on). The phylum takes its name from its distinctive jointed appendages, which may be modified in a number of ways to form antennae, mouthparts, and reproductive organs.