Ch 28- Arthropods and Echinoderms Phylum Arthropoda Most diverse and successful animals of all time Segmented body, tough exoskelton, jointed appendages Classified based on number and structure of their body segments and appendages Mouthparts Major groups include crustaceans, spiders and insects

Crustaceans Subphylum Crustacea Primarily aquatic Crabs, shrimps, lobsters, crayfishes and barnacles Have 2 pairs of antennae, 2 or 3 body sections, and chewing mouthparts- mandibles Body is divided into cephalothorax and abdomen 5 pairs of legs

Cephalothorax- formed by fusion of head with thorax Thorax-body part lies just behind head where most internal organs are Abdomen- posterior part of arthropod’s body Carapace- part of exoskeleton that covers cephalothorax Mandible- mouthpart adapted for biting and grinding food Chelipeds- first pair of legs, have large claws for catching, picking up, crushing, and cutting food Swimmerets- flipperlike appendages used by decapods for swimming Barnacles- sessile, no abdominal segments and don’t use mandibles Attach themselves to rocks and marine animals

Spiders and Their Relatives Subphylum Chelicerata- Chelicerates Horseshoe crabs, spiders, ticks, and scorpions 2 body sections- cephalothorax and abdomen 4 pairs of walking legs Lack antennae Book gills or book lungs Chelicerae- mouthpart that contains fangs, used for stabbing and paralyzing prey Pedipalps- long and modified for grabbing prey

Horseshoe crabs- oldest living arthropods Chelicerae 5 pairs of walking legs Long spikelike tail Spiders- largest group of arachnids Spin silk webs No teeth, paralyze prey and use digestive enzymes to break down prey’s tissue Spinnerets- organs that contain silk glands Video -- Black Widow: Most Venomous Spider in North America -- National Geographic Mites and ticks- often parasitic Chelicerae- needlelike structures used to pierce skin and suck blood Scorpians- widespread in warm areas Pedipalps enlarged into claws Venomous stinger Chew prey using chelicerae

Insects and their Relatives Subphylum Uniramia or uniramians- centipedes, millipedes, and insects Most species of all animals Jaws, one pair of antennae, unbranched appendages Centipedes- class Chilopoda Few to 100 pairs of legs One pair per body segment Carnivores Moist or humid areas Millipedes- class Diplopoda 2 pairs per body segment Feed on dead, decaying plant material

Sec 3- Insects What are the distinguishing features of insects? Body divided into 3 parts- head, thorax, and abdomen 3 pairs of legs attached to thorax

Metamorphosis Process of changing shape and form Under go either incomplete or complete metamorphosis Incomplete metamorphosis- immature forms of insects look very much like adults Nymphs- immature forms of adult insects Lack functional sexual organs and wings Complete metamorphosis- eggs hatch into larvae, look and act nothing like their parents and feed in different ways Larva- look and act nothing like parents, feed in different ways and grow rapidly, molt a few times Pupa- insect changes from larva to adult Video -- Animals, Travel, Kids -- National Geographic

Sec 4- Echinoderms What are the distinguishing features of echinoderms? Spiny skin, internal skeleton, water vascular system, tube feet Most exhibit 5-part radial symmetry Phylum Echinodermata Endoskeleton- an internal skeleton formed of hardened plates of calcium carbonate Live only in the sea Deuterostomes

Water vascular system- system of internal tubes, carries out many essential functions- respiration, circulation, movement Madreporite- sievelike structure through which water vascular system opens to outside Tube foot- structure that operates like suction cup, allows echinoderms to walk and pull open shells

Groups of Echinoderms 7000 species of echinoderms Live in oceans Sea urchins and sand dollars, brittle stars, sea cucumbers, sea stars, sea lilies, and feather stars