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 Oligochaeta- means “few bristles” Earthworms

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

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

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

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

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

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

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

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

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

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

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