BIO2231 Chapter Notes -Malpighian Tubule System, Gastrointestinal Tract, Circulatory System
Document Summary
They have segmented bodies, a chitinous cuticle often containing calcium, and jointed appendages. The critical stiffening of the cuticle to form a jointed exoskeleton is sometimes called. Arthropods diversified greatly, but it is relatively easy to identify particular body plans characterizing arthropod subgroups. For example, centipedes and millipedes have trunks composed of repeated similar segments, whereas spiders have two distinct body regions and lack repeated segments. Why have arthropods achieved such great diversity and abundance: a versatile exoskeleton. Arthropods possess an exoskeleton that is highly protective without sacrificing flexibility or mobility. This skeleton is the cuticle, an outer covering secreted by the underlying epidermis. The cuticle consists of an inner, relatively thick procuticle and an outer, relatively thin epicuticle. Both the procuticle and the epicuticle each consist of several layers (lamina). The outer epicuticle is composed of protein, often with lipids. The protein is stabilized and hardened by chemical cross-linking, called sclerotization, which increases its protective ability.
