1. Ch.18, 19 and 20
Phylum Arthropoda

2. Arthropoda The most diverse and numerous of all animal phyla
Joint-foot
900,000 species
More beetles than all vertebrates(species)

3. Evolution of Arthropods
Natural selection
Fewer body segments
Specialized appendages
Tagmata – head , thorax, abdomen
Cephalothorax, abdomen

4. Phylum Arthropoda 4 subphyla Trilobita-extinct
Chelicerata-chelicerae-2 body segments – 4 pairs of walking legs
Crustacea-2 pair antennae-mandibles
Uniramia-jaws-one pair of antennae-unbranched appendages-3 pairs

5. Arthropoda Cambrian period 570 million years ago Exoskeleton developed
Molting/hormonal control
Hydrostatic skeleton lost – replaced by open system

6. Annelids-Arthropods Shared ancestor coelom Segmented body
Open circulatory system

7. Common Characteristics
Cephalization – eyes, fused ganglia, antennae(fiirst to form images)
Metemerism – somites are very specialized
Paired jointed appendages
Exoskelton
Complex social structures
Protective coloration

8. Characteristics Bilateral symmetry Head, thorax, tail
Cephalothorax, abdomen
Complete digestive system
Respiration – body surface, gills, tracheael tubes or book lungs
Air enters through spiracles
Paired excretory glands-
malpighian tubules

9. Nervous system Brain Well developed system
Compound eyes 2000 separate lenses
Color and motion

10. Versatile Exoskeleton
Cuticle secreted by the epidermis
Made of several layers secreted during molting
Exocuticle first then endocuticle
Layers made of chitin
Tough resistant nitrogenous polysaccharide

11. Insoluble in water and weak acids
Protection, coloration, movement
To grow must shed the exoskeleton or molt
Limits body size – no giant arthropods

12. Segmentation Each somite – jointed appendages Often modified
Hollow levers that are moved by internal muscles
Sensory hairs – modified for sensory functions, food handling, swift walking and swimming

13. Air piped directly to cells
Efficient tracheal system of air tubes
Oxygen delivered directly to tissues and cells
Makes high metabolic rate possible
Limits body size
Some use gills

14. Complex behavior patterns
Inate controls most activities
Some learning
Complex societies and division of labor

15. Metamorphosis Larval state to adult stage
Adapted for different ecological niches
Less competition among the species
Incomplete or Complete

16. Reproduction Sexes usually separate Internal fertilization
Live, eggs, eggs inside or attached

17. Trilobita Before Cambrian period 200 million years ago
Abundant during the Cambrian and Ordovician periods
Trilobed shape of body
Bottom dwelling scavengers
Could roll like pill bugs

18. Chelicerata Horseshoe crabs Spiders Ticks Mites
Scorpions and sea spiders
Name for mouth parts called Chelicerae

19. 3 classes Merostomata Pycnogonida Arachnida Horseshoe crabs
Sea spiders
Scorpions, spiders, ticks, mites

20. Characteristics 6 pairs of appendages
1 pair of chelicerae – suck liquid from prey
Pedipalps
4 pairs of walking legs
No mandibles
No antennae

21. Subphylum Crustacea 5 classes Lobster Crab Shrimp
Pill bug or sow bug - terrestrial
Named after hard outer shell

22. Uniramia 5 classes Chilopoda – centipedes Diplopoda – millipedes
Pauropoda – small soft bodied myriads
Symphyla – small centipede like animals
Insecta – grasshopper to bumble bee to beetle

23. 200 million insects for every singe human
Evolved wings 250 million years before reptiles