Annelids

6S 26 Wong Nga Man

Structure

• Soft-bodied

• Consist of segments (segmentation)

• It composed of three layers of cells (triploblastic)

• Process well-developed alimentary and nervous system

• Without appendages

Locomotion

• Many annelids move by peristalsis

• They have no appendages which will interfere their motion

Reproduction

• Asexual reproduction

• by dividing into two or more pieces or by budding off ,a new individual while the parent remains a complete organism

• They use similar mechanism to regenerate after severe injury

• Example: earthworm

• Sexual reproduction

• Earthworm is hermaphrodites • They release their egg and their partner sperm into

cocoon.

3 typical examples:

• -Bristleworms

• -Leeches

• -Earthworms

Bristleworms

• It is a polychetaes.

• Are found in marine environment

• Process chetae

Earthworm

• -subterranean

• -process annular , streamlined body which allow them passage through the soil smoothly

• Secret fluid over the body to reduce friction

Leeches

• Both aquatic of terrestrial

• Blood-sucking worms

• each one of them has both female and male reproductive organ.

Fossil records

• It is rare to find a fossil of annelids since they are soft bodied

Ecological significance

• For example , earthworm can facilitate the growth of producer.

• They also support the bird’s population.

Medical use

• Both earthworm and leeched have high medical value.

The End