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Phylum Annelida is a very broad phylum belonging to the kingdom Animalia.

Phylum Annelida is a very broad phylum belonging to the kingdom Animalia. The Annelids are found in aquatic as well as terrestrial environments. These are bilaterally symmetrical invertebrate organisms. Their segmented body distinguishes them from any other organism.

The characteristics of the organisms present in the Phylum Annelida are as follows:

The Annelids are coelomate and triploblastic.

They exhibit organ level organization.

They respire through their body surface.

Nephridia are the excretory organs.

They have a well-developed circulatory and digestive system.

Their body contains haemoglobin, which gives them a red colour.

Regeneration is a very common characteristic of the Annelids.

Most of the Annelids are hermaphrodite, i.e., male and female organs are present in the same body. They reproduce both sexually and asexually. The others reproduce sexually.

Following are the different classification of Annelida:

The body is elongated and divided into segments.

They are found in the marine environment.

These are true coelomates, bilaterally symmetrical worms.

They excrete through metanephridia and protonephridia.

They have a well-developed nervous system.

The circulatory system is closed type.

They might possess fin-like appendages called parapodia.

The organisms belonging to this group lack clitellum and are dioecious.

They are mostly freshwater and terrestrial organisms.

The body is segmented metamerically.

Head, eyes and tentacles are not distinct.

They are hermaphrodites, but cross-fertilization takes place.

They do not possess parapodia but clitellum is present.

The organisms belonging to this class are monoecious.

They exhibit no free larval stage and the development takes place inside the cocoons.

Most commonly found in freshwater. Some are marine, terrestrial, and parasitic.

The tentacles, parapodia, and setae are not present.

The body is dorsoventrally or cylindrically flattened.

They have an anterior and posterior sucker on the ventral side.

There is no larval stage during the development of the organism.

The mouth is located ventrally in the anterior sucker, while the anus is present dorsally in the posterior sucker.

They are found only in the marine environment.

The body is elongated without setae and parapodia.

They are unisexual or hermaphrodite.

Tentacles are present on the prostomium.

In conclusion, members of Phylum Annelida have bodies that are segmented, such as leeches and  earthworms .

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