Arthropods …..or “the most successful animals of all time”. aka “bugs”.

Arthropods Segmented bodies- evolution moved to fewer segments and more specialized Jointed Appendages includes legs and antennae Exoskeleton of Chitin Protection conserve water Classified by number of legs and body segments

Feeding All possibilities: herbivores, carnivores, omnivores, filter feeders, bloodsuckers, …

Respiration Gills or Book gills- crabs, crayfish, lobster Book lungs- layers of respiratory tissues stacked like pages of books: spiders Tracheal Tubes- mostly terrestrial- air enters and exits spiracles (small openings).

Circulation Open system Heart  arteries sinoid spaces sinus (vein) heart…

Excretion Terrestrial Aquatic Malpighian tubules sac like organs that extract wastes from the blood and then add to feces or digestive wastes Aquatic diffusion to surrounding water

Response well developed: all have brains and nervous system.

Movement well developed groups of muscles (needs nervous system) opposing muscles: extenders and flexors.

Reproduction Some have internal and some have external All lay eggs

Growth Molting- outgrows their exoskeletons 1. Skin glands 2. Secrete new soft skeleton 3. Pulls out of old skeleton 4. “Puffs” up to increase size and new exoskeleton hardens.

How are Arthropods grouped? Classified based on number and structure of body segments and appendages, particularly mouthparts.

Classes of Arthropods Crustaceans- crabs, shrimp, lobster, crayfish, barnacles 2 pair branched antennae 2 body segments Cephalothorax 5 pairs of legs (the first pair is the claws) Abdomen Compound eyes Have CaCO3 in Chitin for strength

Chelicerates (Arachnids) horseshoe crabs, spiders, scorpions, ticks 2 Body segments 4 pair of legs Mouthparts Chelicerae - fangs: stab and paralyze prey Pedipalps - grab prey Book lungs or book gills