1. Phylum Arthropoda Insects Arachnids Crustaceans
Makes up 3/4'ths of all animal species -total number is MORE than all other species combined

2. Characteristics
Arthropod means "jointed foot" - all arthropods have jointed appendages
Segmented body
Three segments
-----> Head | Thorax | Abdomen
Some have fused head and thorax
-- the cephalothorax

3. Exoskeleton made of chitin for protection & support
shed during molting
Open circulatory system
Compound eyes (many units)
Excretory structures called Malpighian tubules
Respiration using spiracles

4. Taxonomy

5. Subphylum Chelicerata Includes the Class Arachnida spiders, ticks, scorpions, and horseshoe crabs
Have a cephalothorax and abdomen
No antenna
Have 6 pairs of jointed appendages:
*Chelicerae - claws or fangs (1 pair) - (spiders have venom)
*Pedipalps - used for feeding, sensing, transferring sperm (1 pair)
* Walking legs - movement (4 pairs)    
Spinnerets in spiders make webs

6. Spider

7. Subphylum Crustacea Include shrimp, lobster, barnacles, & crabs
Terrestrial crustaceans called isopods (pillbugs or rollypollys) lobsters, barnacles are sessile, freshwater members include crayfish and daphnia
All have mandibles for chewing or tearing
Have cephalothorax & abdomen
Have 10 pairs of jointed appendages
Breathe through gills

8. Some Crustaceans

9. Subphylum Uniramia Includes 2 classes --- Chilopoda (centipedes), Diplopoda (millipedes)
Class Chilopoda - means "100 legs"
Centipedes (predators)
Flattened body
Have 1 pair of legs per body segment
Pincers can inject venom

10. Class Diplopoda - means "1000 legs"
Millipedes
Have 2 pairs of legs per body segment
Rounded body
Scavengers or herbivores

11. Class Insecta 3 body parts - head, thorax, abdomen Six legs (3 pairs)
All appendages attach to the thorax
Mandibles for chewing
*Can have wings

12. Insect Life Cycle Metamorphosis - dramatic physical change
Complete metamorphosis:
Egg --> Larva --> pupa ---> adult (ex. butterflies)

13. Incomplete metamorphosis:
Egg --> nymph --> adult (ex. grasshopper)