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Chapter 28 Arthropods and Echinoderms

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Chapter 28 Arthropods and Echinoderms. Introduction to Arthropods. “jointed feet” Most diverse and successful animals Over 750,000 species identified Segmented bodies Tough exoskeleton Jointed appendages. Body Terms. Exoskeleton - external skeleton that protects and supports the body

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Chapter 28 Arthropods and Echinoderms

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  1. Chapter 28 Arthropods and Echinoderms

  2. Introduction to Arthropods • “jointed feet” • Most diverse and successful animals • Over 750,000 species identified • Segmented bodies • Tough exoskeleton • Jointed appendages

  3. Body Terms • Exoskeleton- external skeleton that protects and supports the body • Made of protein and a carbohydrate called chitin • Much variation on exoskeletons • Terrestrial arthropods (Ter. Arth.) have waxy covering to prevent water loss • Appendages- structures like legs and antennae that extend from the body wall

  4. Evolution has led to: • Fewer body segments • The body segments fused together • Highly specialized appendages • For feeding, movement, and more • Legs became: antennae, claws, wings, flippers, tails, mouthparts and walking legs

  5. Form and Function • Feeding • Varied eating habits- herbivores, carnivores, omnivores • Bloodsuckers, filter feeders, detritivores, parasites • Varied mouthparts- pincers, fangs, jaws

  6. Respiration • Tracheal tubes- branching, air filled tubes that are in many ter. arth. • Spiracles- small openings alongside the body that allow air to enter and leave the tracheal tubes • Book lungs- organs with layers of respiratory tissue stacked ex) spiders • Gills- used by aquatic arthropods ex) crabs • Book gills- used by horseshoe crab

  7. Circulation • Open circulatory system- well developed heart pumps blood  arteries  tissues sinus  collects around the heart and re-enters to be pumped through again

  8. Excretion • Malpighian tubules- saclike organs that extract wastes from blood and add them to feces to move through the gut • Used in ter. Arth. • Diffusion- moves cellular waste from the body to the water • Used in aquatic arth.

  9. Response • All have a brain • Well developed nervous system • Two nerves around the esophagus connect brain to the central nervous cord • Connects the ganglia which coordinate movement of legs and wings

  10. Movement • Well developed muscles controlled by nervous system • Individual muscles cells • Muscles generate force (to fly, walk, swim) by contracting a muscle and pulling on the exoskeleton

  11. Reproduction and Molting • Terrestrial • Internal fertilization • Aquatic • Internal and external fertilization • Molting • When an arthropod sheds its entire exoskeleton and makes a larger one in its place • Controlled by the endocrine system with hormones

  12. Subphyla of Arthropods • Crustacea – crabs, shrimp, crayfish • Chelicerata – spiders, ticks, scorpions • Uniramia – millipedes, centipedes • Class Insecta (no subphylum)– 3 part body, 3 pairs of legs

  13. 28-4 Echinoderms • “spiny skin” • Endoskeleton- hardened plates of calcium carbonate • Gives bumpy, irregular surface • Only live in the sea • No cephalization • Two sided- oral (with mouth)/aboral

  14. Echinoderm Characteristics • Spiny skin • Internal skeleton • Water vascular system • Suction cup structure called tube feet • 5 part radial symmetry • Larvae- bilaterally symmetrical • Deuterostomes

  15. Water Vascular System • Carries out essential body functions like respiration, circulation and movement • Madreporite- opening to the outside through which water passes • Connects to ring canal which extend out into radial canals along the 5 arms • Tube feet- suction cups on the underside of the body that help with movement and feeding

  16. Feeding • Urchins- scrape algae • Sea lilies- capture floating plankton • Sea cucumbers- take in sand and detritus off sea floor • Sea stars- use tube feet to pull open bivalves, push stomach out, pour enzymes and digest mollusks, brings back stomach into body

  17. Respiration and Circulation • Water vascular system • Thin walled tissues of tube feet for respiration • Skin gills gas exchange

  18. Excretion • Digestive wastes- feces through anus • Ammonia excreted through tube feet

  19. Response and Movement • Don’t have highly developed nervous system • Nerve ring around the mouth • Sensory organs that detect light • Tube feet • Endoskeleton structure/flexible joints

  20. Reproduction • External fertilization • Separate sexes

  21. Groups of Echinoderms • Urchins • Sand dollars • Brittle stars • Sea cucumbers • Sea stars • Sea lilies • Feather stars

  22. Ecology • Urchins control algae • Sea stars control clams and corals • Crown of Thorns • Feeds on corals • Rows of poisonous spines on arms • Great Barrier Reef damage

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