1. Phylum Arthropoda Spiders, crabs, millipedes, insects, scorpions and lobsters

2. General information  Largest animal group  Have segmented bodies  Bilateral symmetry, 3 cell layers and a coelom  Phylum name means “jointed feet”  Has an exoskeleton made out of protein and chitin (this is heavy and cumbersome, so arthropods can only get so large before they would collapse under there own weight)

3. Such a big group it is divided into four “subphyla”  Trilobita: extinct now  Chelicerta: spiders, scorpions, etc  Crustacea: crabs, lobsters, etc  Uniramia: millipedes, centipedes and all insects

4. Subphylum Chelicerta Class Arachnida  Spiders, scorpions, ticks, mites…..  All have 4 pairs (8) walking legs  Most are carnivorous

5. Subphylum Chelicerata Class merostomata: horseshoe crabs  “living fossils”  Not really crabs at all

6.  All chelicerates have a body divided into a cepalothorax and abdomen  Unique to chelicerates are two pairs of appendages attached near mouth:  Chelicerae : spiders use these to bite/paralyze prey, and then inject enzymes that liquefy the prey so they can suck the “juice” out  Pedipalps : for handling prey, scorpions have large ones modified into claws

8.  All spiders produce silk, some spin webs using “spinnerets”  Ticks and mites are usually parasites

9. Subphylum Crustacea (not focusing on one class)  Crabs, prawns, lobster, crayfish, copepods, water fleas….  Primarily aquatic  Vary widely in size (microscopic to 6 m)  Usually have a hard skeleton reinforced with calcium  Usually have 2 pairs of antennae and a pair of mandibles

10.  Have a head, thorax and abdomen  (these may be fused into cephalothorax)  Appendages vary greatly, crayfish have claws, walking legs, swimmerets and uropods

13. Subphylum Uniramia Class chilipoda  Centipedes  I pair of legs per segment  carnivores

14. Subphylum Uniramia Class Diplopoda  Millipedes  2 pairs of legs per segment  scavengers

15. Subphylum Uniramia Class Insecta  HUGE group  All have head, thorax and abdomen  3 pairs of legs attached to thorax