Mollusks and AnnelidsSection 2 Phylum Annelida: Segmented Worms

Mollusks and AnnelidsSection 2 Phylum Annelida Class Oligochaeta, earthworms Class Polychaeta, (Poly = many, Chaeta = bristle) Class Hirundinea, leeches

Mollusks and AnnelidsSection 2 Characteristics of Annelids Coelomates Have segments Highly specialized organ systems. Most annelids have external bristles called setae

Mollusks and AnnelidsSection 2 Characteristics of Annelids First organisms to have a body plan based on repeated body segments. –Septa separate segments. Each segment has its own fluid-filled cavity which contains a part of the animal’s coelom. –digestive, excretory, and circulatory organs, loco - motor organs

Mollusks and AnnelidsSection 2 Characteristics of Annelids Segmentation –greater freedom of movement –greater complexity of body organization Well-developed cerebral ganglia Annelids reproduce sexually, –trochophore larva only in polychaetes

Mollusks and AnnelidsSection 2 Annelid Diversity Grouped based on –the number of setae (bristles) that they have –the presence or absence of parapodia (fleshy extensions) –which are flap-shaped appendages used for gas exchange and locomotion. Marine worms, earthworms, and leeches are examples of annelids.

Mollusks and AnnelidsSection 2 Class Oligochaeta

Mollusks and AnnelidsSection 2 Visual Concept: Movement of an Earthworm Feeding Habits of an Earthworm

Mollusks and AnnelidsSection 2 Class Hirundinea (Leeches) Smallest class of Annelids Leeches live in calm bodies of fresh water Suckers at both ends of its body Segments are not separated internally. Lack both setae and parapodia

Mollusks and AnnelidsSection 2 Leeches Predators or scavengers; small number are parasites Parasitic leeches secrete chemicals called anticoagulants –Hirudin Secrete an anesthetic

Mollusks and AnnelidsSection 2 Class Polychaeta

Mollusks and AnnelidsSection 2 Class Polychaeta Many bristles Only annelid with trochophore larva Antennae and specialized mouthparts Marine habitats Sessile and free – swimming –Filter – feeders or jaws for prey