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Annelida – Definition, Classification, Characteristics, FAQs

Last Updated : 17 Aug, 2022
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The shape, make-up, and way that different species live are different. They ought to be grouped together as a result of their similarities. The grouping of creatures that are linked helps with the study of their connections throughout evolution. Organisms are divided into classes and subgroups based on this process, which is referred to as classification.

A particular shape or function could be a trait. The bulk of living things on Earth today is the outcome of a sequence of physical alterations that allow the possessing beast to their betterment in life. It’s possible that design complexity will increase with time, and To imply that ancient species are easier and less complex is not unreasonable. More complex organisms are younger ones.




Animalia’s phylum Annelida is one of the largest in the animal kingdom. Both aquatic and terrestrial settings support annelids. These invertebrate species have bilateral symmetry. They can be distinguished from other organisms by their segmented bodies.


The following are some traits of the creatures that make up the Phylum Annelid:

  • The annelids are triploblastic and coelomate.
  • Organ system-level organizations can be seen in them.
  • They have distinct bodily parts.
  • Through the surface of their body, they breathe.
  • The excretory organs are nephroid organs.
  • They have well-established digestive and circulatory systems.
  • They are red because of the hemoglobin in their bodies.
  • For Annelids, regeneration is a relatively common trait.
  • Setae facilitate their mobility.
  • The majority of annelids are hermaphrodites, meaning that they have both male and female organs in the same body. They have both sexual and asexual reproduction. The others use sexual reproduction.
  • Example: Leeches, earthworms.

Frequently Asked Questions

Question 1: Appendages of the polychaeta?


Polychaeta would have fin like appendages and this would help to the polychaeta to run down the water.

Question 2: How suckers would be helpful for Hirudinea?


Similar to an inchworm’s locomotion, leeches move through solid substrates by alternating the connection of their anterior suckers and the posterior suckers during intervals of body stretching.

Question 3: How is Hirudinaria used to treat diseases?


Hirudin present in these annelids dissolve the blood clots, so it would play an essential role after surgeries

Question 4: Why do Annelids exhibit triploblastic nature?


They would possess the three germ layers, so the annelids would be consists of triploblastic.

Question 5: What causes mobility in annelids?


Setae would help in mobility by Certain body muscles to extend a segment’s setae to stop the segment from moving backward when the longitudinal muscles contract.

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