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Chapter 13

Chapter 13. Invertebrates Part II Mollusks, Worms, Arthropods & Echinoderms. Ch 13.1 - Mollusks. A. Mollusks – soft bodied invertebrates with bilateral symmetry and usually 1 or 2 shells 1. Mantle – thin layer of tissue that covers organs and secretes shell

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Chapter 13

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  1. Chapter 13 Invertebrates Part II Mollusks, Worms, Arthropods & Echinoderms

  2. Ch 13.1 - Mollusks A. Mollusks – soft bodied invertebrates with bilateral symmetry and usually 1 or 2 shells 1. Mantle – thin layer of tissue that covers organs and secretes shell 2. Mantle Cavity – b/w body and mantle; sometimes contains gills

  3. 3. Open Circulatory System – blood moves in open spaces around organs 4. Sensory Organs – well developed head and mouth

  4. 5. Foot – muscular underside of body used to move

  5. 6. Radula – tongue-like organ with teeth used to get food

  6. B. Mollusks are classified into 3 groups 1. Gastropods – have 0 or 1 shell a) Include snails, conchs and slugs

  7. c) Glands in the foot secrete a layer of mucus for sliding

  8. 2. Bivalves – have hinged 2 part shell a) Include clams, oysters and scallops

  9. 3. Cephalopods – most complex mollusks; shell secreted internally a) Include squid, octopuses, cuttlefish and chambered nautiluses

  10. Giant Squid

  11. Octopus

  12. Cuttlefish

  13. Chambered Nautilus

  14. b) Well developed head and many tentacles for capturing prey c) Closed Circulatory System – all blood in vessels d) Fossils date to more than 500 million years ago e) Jet Propulsion – move at 6 m/s

  15. C. Uses of Mollusks 1. Food for people and other animals 2. Pearls and shells used for jewelry and decorations

  16. Ch 13.2 – Segmented Worms A. Segmented worms – AKA annelids 1. Bilateral symmetry 2. Body cavity with organs 3. Two body openings (mouth & anus)

  17. 5. Includes earthworms, marine worms and leeches 4. Setae – bristle-like structures used to hold on to and move in the soil

  18. B. Earthworms - more than 100 segments 1. Move with 2 sets of muscles 2. Have closed circulatory system and small brain 3. Breath through mucus covered skin 4. Are hermaphrodites but must exchange sperm with another worm

  19. 5. Digestive System a) Mouth – ingests soil b) Crop – food storage area c) Gizzard – grinds food d) Intestines – releases nutrients e) Anus – eliminates wastes which fertilizes soil

  20. Earthworm Anatomy

  21. C. Marine Worms – (AKA polychaetes) have segments with setae in bundles 1.Some are sessile and build tubes around their bodies for protection

  22. 2. Some are free swimming

  23. D. Leeches – segmented worms w/o setae that feed on blood of other animals

  24. 1. Used in medicine to prevent blood from coagulating after surgery

  25. 2. Chemicals released being studied as treatments for heart disease, strokes, arthritis and glaucoma

  26. E. Uses of Segmented Worms 1. Aerate soil 2. Provide food for fish 3. Produce medically useful chemicals F. Seg. Worms probably evolved in the sea and had a common ancestor w/ mollusks

  27. Ch 13.3 - Arthropods A. Characteristics 1. Jointed appendages 2. Bilateral symmetry 3. Most species have separate sexes 4. Some have body segments while others have fused areas called regions

  28. 5. Exoskeletons – hard, thick outer covering that protects and supports a) Molting – process of shedding and replacing the exoskeleton

  29. B. Insects 1. Have 3 body regions: a) Head – antennae, eyes & mouth b) Thorax – 6 legs & wings (if present) c) Abdomen – reproductive structures, open-circulatory sys. & respiratory sys. - contains pores for gas exchange called spiracles

  30. 2. Undergo Metamorphosis – series of changes in body from birth to adult a) Incomplete Metamorphosis - egg, nymph, adult

  31. b) Complete Metamorphosis - egg, larva, pupa, adult

  32. 3. Eat plants, blood, nectar, wood, decaying materials, and cloth a) mouth parts are diverse and adapted to their diet

  33. 4. Insects are successful due to: a) exoskeltons b) ability to fly c) rapid reproductive cycles d) small size

  34. C. Arachnids 1. Have 2 body regions a) Cephalothorax – head & chest; b) Abdomen – reproductive structures 2. Includes spiders, scorpions, mites & ticks

  35. a) Spiders – 8 legs & no antennae; cannot chew their food so they have venom glands that release enzymes to digest food into a liquid then suck it in

  36. b) Scorpions – have sharp, poison-filled stinger at the end of their abdomen

  37. c) Mites – many are plant and animal parasites but some are not such as ones that live in human eyelash follicles; look like tiny specs to human eye

  38. d) Ticks – all are parasites that attach to host’s skin and suck blood; many carry disease

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