What are the 3 groups of annelids?
Critical appraisal. Most authors accept the annelids as having three major classes: Polychaeta, Oligochaeta, and Hirudinea. Older systems would place the polychaetes and oligochaetes under the class Chaetopoda because both groups possess setae.
What symmetry does an annelid have?
Annelids display bilateral symmetry and are worm-like in overall morphology. They have a segmented body plan where the internal and external morphological features are repeated in each body segment.
What is the most distinguishing characteristic of annelids?
So the correct answer is ‘Metameric segmentation’.
What characteristics do polychaetes have?
The known species of polychaetes share only a few characteristics. Each has a head, a tail and a segmented body, and typically each body segment has a pair of leg-like parapodia with spiny bristles sticking out. It’s these bristles that give the worms their name: “polychaete” is Greek for “with much hair.”
What are 5 examples of annelids?
Examples of Annelids
What is the most obvious feature of Polychaetes?
Polychaetes are particularly common on and in muddy and sandy shores. Their most obvious feature are the pairs of parapodia appendages. One pair comes from each body segment. These parapodia are used for crawling and swimming.
What type of worms are Polychaetes?
Polychaetes, which include rag worms, lugworms, bloodworms, sea mice, and others, are marine worms notable for well-defined segmentation of the body. Unique among annelids, most polychaete body segments bear a pair of parapodia (flat, lobelike outgrowths) with setae, or tiny bristles.
What is the difference between Metameres and Septa?
What is the difference between metameres and septa? External segments are called metameres and internally, septa, or dividing walls, are located between the segments.
What are the characteristics of an earthworm?
An earthworm has a streamlined body with no antennae or fins or arms or legs! This streamlined shape is an adaptation to living in narrow burrows underground and the need to move easily through the soil. An earthworm has circular muscles that surround each body segment.
What are the characteristics of a segmented worm?
Segmented worms are bilaterally symmetrical. Their body consists of a head region, a tail region, and a middle region of numerous repeated segments. Each segment is separate from the others by a structure called septa. Each segment contains a complete set of organs.