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Chapter 35

Chapter 35. Section 2 Annelida. Characteristics Annelida. Segmented worms Coelomates- true body cavity Setae - external bristles Parapodia - fleshy protrusions Three classes: Oligochaeta, Polycheata, & Hirudinea. Class Oligochaeta. Live in the soil, freshwater, and have no parapodia

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Chapter 35

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  1. Chapter 35 Section 2 Annelida

  2. Characteristics Annelida • Segmented worms • Coelomates- true body cavity • Setae- external bristles • Parapodia- fleshy protrusions • Three classes: Oligochaeta, Polycheata, & Hirudinea

  3. Class Oligochaeta • Live in the soil, freshwater, and have no parapodia • Oligochaeta- means “few bristles” • Earthworms

  4. Structure & Movement • Body divided into over 100 segments • Contraction of muscles helps earthworm move • Locomotion in earthworms is an example of movement made possible by segmentation

  5. Feeding & Digestion • Ingest soil as they burrow • Soil  mouth  esophagus  crop  gizzard  intestines  anus • Crop- temporary storage area • Gizzard- grinds the food for digestion

  6. Feeding & Digestion • Typhlosole- in-folding of intestinal wall; increases surface area available for digestion • Fertilize soil by releasing nutrients • Aerate soil, making it easier for roots to grow

  7. Circulation • Closed-circulatory system • Aortic arches- five pairs of muscular tubes; link the dorsal and ventral blood vessels near the anterior end of the worm • Contractions of dorsal blood vessel and aortic arches force blood through body

  8. Respiratory & Excretion • Earthworms stay in moist environments to avoid drying out because gas exchange occurs through skin • Secrete mucus & have cuticle • Nephridia- eliminate cellular waste & excess water through tubules

  9. Neural Control • Anterior end- cerebral ganglia- ventral nerve cord • Sense light, touch, chemicals, moisture, vibrations, & temperature

  10. Reproduction • Hermaphrodites • Press ventral parts together and held together by clitellum- thick part of worm and mucus • Each worm injects sperm into mucus which move to the seminal receptacle- sperm is stored

  11. Reproduction • Clitellum of each worm secretes a tube made of chitin- tough carbohydrate • The tube picks up the sperm and eggs and the eggs are fertilized and grow in the tube and hatch 2-3 weeks later

  12. Class Polychaeta • Polychaeta- “many bristles” • Only annelids with trochophore stage • Live in marine environments • Feed on sediments or small animals

  13. Class Hirudinea • Leeches • No setae or parapodia • Sucker present to “hook” onto host • Move by swimming or using their sucker to crawl on prey

  14. REVIEW!!! • Name the three different classes of the Phylum Annelida and an example of each class. • Explain how earthworms feed. • Explain how earthworms reproduce.

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