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Annelida

Annelida. Characteristics of Annelida. Segmentation – both internal (septae) and external - phylum includes earthworms, leeches, and a large number of mostly marine worms known as polychaetes . (There are about 9000 species of annelid known today)

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Annelida

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  1. Annelida

  2. Characteristics of Annelida • Segmentation – both internal (septae) and external - phylum includes earthworms, leeches, and a large number of mostly marine worms known as polychaetes. (There are about 9000 species of annelid known today) • Coelom – lined with mesoderm, fluid filled cavity which separates body wall from the intestine; independent movements, tube within a tube

  3. Characteristics (continued) • Advanced Organ Structures 1 way digestive tract with 2 openings (specialization) Chemical and mechanical digestion Closed circulatory system ** Ventral nerve cord with ganglia

  4. Classes • Leech • Nereis • Oligochaetes - earthworms

  5. Leech • Anterior sucker and larger posterior sucker for attachment • Anterior teeth for penetration

  6. Nereis • Distinct head projections: tentacles, eyes, mouth (sensory functions) • Parapodia:fleshy lateral extensions per segment with setae, function in locomotion and respiration

  7. Figure 33.23x External anatomy of an earthworm

  8. Figure 33.23 Anatomy of an earthworm

  9. Physiology of Earthworm • Locomotion- mesodermal muscles and ventral setae, aerates soil • Food-getting- dead vegetation via a muscular phyrynx via the mouth to short esophagus • Digestion- 1-way digestive tract with specialization -esophagus-crop(storage)-gizzard(mechanical digestion)-long intestine(site of extracellular chemical digestion) with typhlosole(dorsal longitudinal fold)-absorption following digestion-anus

  10. Physiology of Earthworm • Excretion- anus-sold wastes(fertilizer for soil) Nephridia-liquid wastes from coelom, open to exterior in each segment • Circulation- Blood moves anteriorly along contractile dorsal blood vessel aided by contraction 5prs of “hearts” or pumps-blood flows posteriorly via ventral blood vessel-blood returns to dorsal vessel segmentally via capillaries that pass enar intestine(nutrient absorption) and through skin (gasous exchange)

  11. Physiology of Earthworm • Respiration- moist skin-gaseous exchange between outside and capillaries of skin -blood contains hemoglobin to aid in gas transport • Nervous system- brain with segmented ganglia -skin richly supplied with sensory receptors • Reproduction- sexual hermaphroditic -male-testes seminal vesicles with opening -female-ovaries with oviducts and -seminal receptacles and clitellum

  12. Figure 33.23 Anatomy of an earthworm

  13. Mollusca • A. Characteristics • 3 body zones: head/foot for sensory • Visceral mass for organs • Mantle membrane covering visceral mass that secretes shell and has cavity Mantle Cavity – lungs or gills, excretion and reproduction 1-way digestive tract Open circulation system Radula – rasp-like file vs. filter feeder (siphons)

  14. Figure 33.16 Basic body plan of mollusks

  15. Figure 33.22 Cephalopods: Squid (top left and bottom left), nautilus (top right), octopus (bottom right)

  16. Figure 33.20 A bivalve: Scallop

  17. Figure 33.19 Gastropods: Nudibranchs (top left and bottom left), terrestrial snail (bottom left), deer cowrie (bottom right)

  18. Figure 33.18x Garden snail

  19. Figure 33.18 The results of torsion in a gastropod

  20. Figure 33.17 A chiton

  21. Figure 33.21 Anatomy of a clam

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