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Arthropods Chapter 13 Section 3 Arthropods Jointed appendages, Bilateral symmetry Segmented bodies Exoskeleton Body cavity Digestive system with two openings Nervous sytsem MOST have separate sexes (not hermaphrodites) Arthropods Some many segments, others have fused segments forming body regions A hard, thick, outer covering called an exoskeleton covers, supports, and protects the arthropod, it is shed and replaced occasionally in a process called molting Insects 3 body regions Insect body regions An insect’s head has a pair of antennae, eyes, and a mouth The thorax has three pairs of legs; if the insect has wings, they are attached to the thorax The abdomen contains reproductive structures and an open circulatory system; insects obtain air and release waste gases through openings called spiracles Metamorphosis Series of body changes as insects become adults Incomplete metamorphosis Egg, nymph adult Complete metamorphosis Egg, larva, pupa, adult Metamorphosis Insects eat plants, blood of animals, nectar, decaying materials, wood, and clothes; mouth parts are diverse and adapted to diet Insects are successful due to their exoskeletons, ability to fly, rapid reproductive cycles and small sizes Arachnids Spiders and ticks have two body regions (the cephalothorax and abdomen), four pairs of legs, and no antennae Scorpions Sharp, poison-filled stinger at the end of their abdomen Spiders Inject their prey with enzymes to digest it. Mites and Ticks Generally diseases parasites; ticks often carry Centipedes and millipedes Long bodies with many segments, many legs, antennae, and simple eyes Crustaceans Crabs, shrimp, and barnacles have one or two pairs of antennae and mandibles for crushing food What arthropods can do! Food source Aid in agriculture, important part of ecological communities in which humans live BAD Some are pests that carry disease or damage property Insecticides Can kill insects, but cause other environmental problems; biological methods for controlling insects are being developed Arthropod fossils Some fossils are more than 500 million years old Probably evolved from a segmented worm ancestor.
