Phylum Annelida: [Annelus-Ring]

• The organisms are commonly known as segmented worms.
• Habit and Habitat: they are free-living organisms found in different habitat like terrestrial [soil] or water both marine and fresh.
• Symmetry: they are bilaterally symmetric [left and right side of the body has same design].
• Body cavity: True coelomic cavity is present so they are known as coelomates or eucoelomates.
• Body differentiation: They are multicellular, real organs present with extensive diffrentiataion.
• Germ layer: They are the first triploploblastic animals.
• Body organization: Body is worm-like, elongated, narrow and cylindrical. Body is metamerically segmented by external grooves and internal septa.
• Skeleton:  Exoskeleton is absent; body is covered with thin moist cuticle.

• Life processes:

1. Alimentary canal/ digestive tract is complete and straight having two openings- mouth and anus.
2. Close blood circulatory system is present. It is the first group to have developed circulatory system.
3. Respiration occurs through skin.
4. Excretion takes place through structures called nephridia present in each segment.
5. Nervous system is comprised of dorsal brain, ventral nerve cord and lateral nerves.
6. They are unisexual or bisexual. Reproduction is sexual.
7. Paired locomotory organs are present [setae or parapodia]

Examples:

Earthworm [Pheretima], leech [Hirudinaria], Neries etc.

Comparison of worms: platyhelminthes, nematode and annelida