What is Phylum Annelida?
- Annelida includes all the organisms which have rings all over their
For example, earthworms.
- Each segment has a set of organs on the inner side. These organisms have developed systems. Annelids have a cylindrical and triploblastic body which originates from all the three embryonic layers namely endoderm, mesoderm, and
Earthworm
- Their body encloses a true body cavity, coelom which makes annelids coelomates.
- The true body cavity has the organs inside it. These organs can be located from the segment number in the
- Many of the annelids dwell on land but most of the subphylum also inhabits marine habitation.
For example, earthworms, leeches, sandworms, lungworms, etc.
Which systems are present in annelids?
- Annelids usually have a well-evolved mouth with a few The digestive system is also very well developed in most of them.
- Excretion is done by specialised cells, metanephridia, or
- The respiratory system is not that well developed. In most cases, the exchange of gases occurs through the skin or simply the cuticle through diffusion. In other cases, the exchange occurs through gills located in a few segments near the anterior
- Annelids have a few ganglia, a collection of neurons, that form rings. These act as the decision-makers for all the systems and bring about the necessary
- Annelids have separate sexes and they reproduce sexually. The fertilisation is mostly external. Some annelids occasionally also opt for asexual reproduction which is shown by the lower members of the family with a less complex
The Internal Structure of Earthworm
Annelids