Exploring Arthropoda: Evolution, Characteristics, and Diversity

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

8. 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 Characteristics

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

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