• 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

• 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

• 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

• 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

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

• 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

• 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 functionsrespiration, 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

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