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Arthropods

Arthropods. Jointed-legged invertebrates. Arthropod Characteristics. Metamerism with tagmatization Chitinous exoskeleton Paired-jointed appendages Growth with ecdysis (molting) Ventral nervous system Open circulatory system Complete digestive tract Malpighian tubules for excretion.

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Arthropods

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  1. Arthropods Jointed-legged invertebrates

  2. Arthropod Characteristics • Metamerism with tagmatization • Chitinous exoskeleton • Paired-jointed appendages • Growth with ecdysis (molting) • Ventral nervous system • Open circulatory system • Complete digestive tract • Malpighian tubules for excretion

  3. Evolutionary Significance • Protostomes • Schizocoelous development • Paired ventral nerve cord • Loss of internal metamerism • Increased tagmatization (specialization of segments)

  4. Terrestrial Dominance • Minimize water loss • Exoskeleton • Respiratory system development • Advanced excretory system • Greater ability for movement • Exoskeleton attaches strong muscles • Support

  5. Exoskeleton • Major reason for success of this group! • Provides • Support • Protection • Prevention of dehydration • Sites for muscle attachment

  6. Exoskeleton Structure • Epicuticle (outer layer) • Water tight • Barrier • Procuticle (inner layer) • Made of chitin • Allows for protection • Forms joints

  7. Ecdysis • Shedding or molting of exoskeleton • New exoskeleton is soft • Tanning (sclerotization) must take place to make outer layer of procuticle hard

  8. Metamorphosis • Change in body form from immature (larval) stages to adult forms • Reduces competition between stages for • Food • Living space • Larval forms often occupy different habitats than the adults do

  9. Taxonomy of Arthropods • 4 subphyla • Trilobitomorpha (all extinct) • Chelicerata • Crustacea • Uniramia

  10. Trilobitomorpha • Trilobites • All extinct • All marine • 3 sections

  11. Chelicerata • Class Merostomata • Horseshoe crabs • Water scorpions (eurypterids) • Class Arachnida • Spiders • Mites • Ticks • Scorpions • Class Pycnogonida (sea spiders)

  12. Chelicerate Characteristics • Two-part body • Opisthosoma • Chelicerae (1st pair of appendages – forms feeding palps or fangs) • Pedipalps (2nd pair of appendages) • Cephalothorax (prosoma) • Book lungs or book gills

  13. Crustacea • Class Malacostraca • Shrimp, lobsters, crayfish • Isopods (wood lice – roly poly) • Amphipods • Class Branchiopoda • Fairy shrimp, brine shrimp • Water fleas

  14. Class Copepoda • Cyclops (freshwater) • Class Cirripedia • Barnacles • Sacculina – parasite of crabs

  15. Crustacean Characteristics • 2 pairs of antennae • Biramous appendages (Y-shaped) • Segments are serially homologous

  16. Uniramia • Class Diplopoda (millipedes) • Class Chilopoda (centipedes) • Class Pauropoda • Class Symphyla • Class Hexapoda (insects)

  17. Insect Locomotion • Flight • Walking (3+ legs on ground at all times) • Running (Can run on 2 legs) • Swimming (legs modified as paddles) • Jumping (saltatory locomotion)

  18. Insect Respiration & Circulation • Respiration • Tracheae & spiracle system • Circulation • Modified open circulatory system • Some vessels • Primitive Heart

  19. Nervous System • Johnston’s organs (hearing - on antennae) • Tympanic organs (hearing – on legs or body) • Compound eyes (facets – ommatidia – fused) • Simple eyes (ocelli)

  20. Metamorphosis

  21. Economic Impact of Arthropods • Name one effect each major group has on mankind (good or bad). • For insects, list 4 good things that they do and 4 bad things that they are responsible for.

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