Arthropods and Echinoderms Animals Chapter 2 sections 3 & 4

Characteristics of Arthropods 75% of all known species Jointed limbs Segmented body Exoskeleton Well developed nervous system

Jointed Legs Arthro means jointed Pod means foot

Segments Some have virtually identical segments (millipede) Some have very different segments (grasshopper)

Exoskeleton External skeleton made of chitin Sheds to allow growth in a process called molting Keeps organism from drying out Protects organism Helps with movement

Nervous System Head and brain Some have simple eyes that can detect light but not make an image Most have compound eyes that allow them to see images Bristles that sense movement, vibrations, chemicals

Centipedes and Millipedes Carnivores 1 pair of legs per segment One pair of antennae Millipedes Herbivores Two pairs of legs per segment One pair of antennae

Crustaceans Shrimp, barnacles, crabs, lobsters Gills Two pair of antennae Eyes on stalks

Arachnids Spiders, scorpions, mites, ticks Two main body parts: cephalothorax – head and thorax (chest) combined abdomen – stomach area No antennae Four pairs of walking legs Chelicerae instead of mandible (pinchers instead of jaw) Eight simple eyes

Insects Largest group of arthropods Live everywhere on earth except oceans Good because pollinate flowers Bad because they are pests, eat crops, can carry disease Three part body – head, thorax, abdomen Some have wings

Metamorphosis- A change in form from egg to adult Incomplete metamorphosis- egg, nymph, adult Baby looks like small adult

Metamorphosis continued Complete metamorphosis Full change from egg to adult Four stages – egg, larva, pupa, adult

Echinoderms Term means “spiny skinned” Has Endoskeleton which is inside the body Water vascular system – water pressure helps with feeding, breathing and movement