Monday, September 12, 2011

An arthropod is a member of the phylum that includes invertebrate animals such as insects, arachnids (scorpions, spiders, etc.), and crustaceans, which have jointed legs and a tough exoskeleton. What differentiate the arthropods are their segmented bodies, jointed legs, and their exoskeleton (outer skeleton). There are more than one million species of arthropods. Since their exoskeleton cannot stretch, restricting growth, arthropods therefore replace their exoskeletons by molting, or shedding the old exoskeleton after growing a new one that is not yet hardened. Molting cycles run nearly continuously until an arthropod reaches full size.