Regular Biology Chapter 27 WAGGY Phylum: Annelida Regular Biology Chapter 27 WAGGY

Chapter Objectives Discuss the general characterisitics of the annelid worms Discuss the taxonomy of worms Describe the specific characteristics of the Polychetes Describe the specific characteristics of the Hirudinea Describe the specific characteristics of the Oligochetes

General characteristics of Annelids Means ‘little rings’ Refers to the segmented bodies Consists of about 15,000 different species All have bilateral symmetry Each segment can constrict & relax independently of each other which is an advantage over the flatworms

Taxonomy 1. Polychaeta 2. Hirudinea 3. Oligochaeta Domain: Eukarya Kingdom: Animalia Phylum: Annelida Class: there are three 1. Polychaeta 2. Hirudinea 3. Oligochaeta

Class: Polychaeta ‘many bristles’ About 2/3’s of all annelids are in the class polychaeta These worms have setae (stiff bristles) to help them move but also have parapodia Parapodia are fleshy outcroppings that act as feet

Class: Polychaeta Most live in marine waters eating organic material from the ocean floor Others are free swimming parasites that attach themselves to sharks & fish

Class: Hirudinea These are the leeches There are only about 500 species of leeches worldwide Most live in calm fresh water but some can live on land where there is constant moisture Leeches do not have setae or parapodia, instead they have a sucker on each end of their body

By attaching one sucker to a surface and then pulling the rest of its body forward it can move along most surfaces like an inchworm Some are carnivorous attacking other invertebrates but some are parasitic by sucking blood from larger warm blooded animals If left undisturbed a single leech can eat 10 times its own body weight in blood!

Class: Oligochaeta (the Earthworms) Generally live in the soil or in fresh water Each segment has a small bundle of bristles called setae on it These setae help the worm grip the soil & burrow The earthworm is a member of this group

Structure & movement… The body is divided into more than 100 segments, most of which are identical Each segment has two sets of muscles: 1. Circular muscles contract to increase the fluid pressure inside the worm This pushes the setae into the soil & pushes the front part of the body forward 2. Longitudinal muscles then contract to pull the body forward

Feeding & Digestion… Earthworms ingest soil as they burrow The soil enters the mouth & into the muscular pharynx It then passes through the esophagus & into a temporary storage organ called the crop When ready, the soil moves into a muscular part of the gut called the gizzard

The gizzard grinds the soil releasing any organic matter The digested organic materials move through the long intestine where nutrients are absorbed into the blood Waste is pushed out of the body through the anus This waste is called castings

Castings play an important role in maintaining the fertility of the soil The burrows made by the worm serves to aerate the soil, allowing air to penetrate the soil bringing oxygen to plant roots & other soil dwellers