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

2. 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

3. 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

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

5. 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

6. 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

7. 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

8. 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!

9. 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

10. 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

12. 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

13. 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

14. 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