4/29/13Objective: Phylum Nematoda and Phylum Annelida

*Take out HW (23.4 and 23.5)

Do Now:a.What kind of symmetry to platyhelminthes have?b.What type of body cavity?

Phylum Nematoda (Roundworms)

• Have bilateral symmetry and 3 tissue layers like flatworms

• Different from flatworms because they have:

• Complete Digestive Tract: - Opposite mouth and anus- Digestive tube

Body PlanPseudocoelm “false cavity”:

- fluid filled body cavity in direct contact with the digestive tract

Diversity

• Most are free-living and decomposers

• Some are Parasites• Ex: Heartworm

Phylum Annelida (Annelids) aka Segmented Worms

Body Plan

- Divided into sections by internal walls-- Digestive tract, nerve cord, and main

blood vessels not segmented

• Have bilateral symmetry and 3 tissue layers

Closed Circulatory System:• Blood remains in vessels

- nutrients, oxygen, and wastes diffuse

Coelom• True, fluid filled body cavity in contact with

internal tissues

Anatomy

• Pharynx: beginning of digestive tract

• Crop: stores food temporarily

• Gizzard: soil mixture is ground up

• Clitellum: area near anterior end• creates cocoons for

offspring• Setae: tiny hairs on

ventral side for movement

Class Polychaeta

Ex: Marine clam worm or “sand worm”

Class Oligochaeta

• Example: Earthworms• Description: Churns and aerates

the soil

Class Hirudinea

• Example: LeechesDescription: Parasitic