- Bilateral symmetry
- Metamerism (segmentation) with specialized segments performing different functions
2. Body Cavity:
- Coelomates, meaning they have a true coelom or body cavity lined with mesoderm
3. Digestive System:
- Complete digestive system with a mouth, digestive tract, and anus
4. Circulatory System:
- Closed circulatory system with blood vessels, including dorsal and ventral blood vessels
5. Excretory System:
- Metanephridia in each segment function as excretory organs
6. Respiratory System:
- No specialized respiratory organs; some exchange gases through their body surface, while others have specialized structures like branchiae in aquatic species
7. Nervous System:
- Ladder-like nerve cord with ventral nerve ganglia in each segment
8. Sensory Organs:
- Simple sensory structures such as antennae, palps, and light-sensitive structures
9. Reproduction:
- Most are hermaphrodites, with both male and female reproductive organs
- Sexual reproduction involving fertilization, either external or internal
10. Habitat:
- Found in a wide range of habitats, including aquatic (marine and freshwater), terrestrial, and semi-terrestrial environments.