Metamerism

Definition

Metamerism is the phenomenon of having a segmented body plan, where the body is divided into repeating units called segments. This feature is prominent in certain invertebrates like annelids and arthropods.

5 Must Know Facts For Your Next Test

1. Metamerism allows for greater flexibility and mobility, as each segment can move independently.
2. In annelids, metamerism is evident through their segmented bodies, which include structures such as paired setae for movement.
3. Molluscs do not exhibit true metamerism, distinguishing them from other members of the Superphylum Lophotrochozoa.
4. Each segment in a metameric organism typically contains replicated organ systems, enhancing survival through redundancy.
5. The development of metamerism is controlled by Hox genes that regulate the formation and differentiation of segments during embryonic development.

Review Questions

• How does metamerism contribute to the mobility of annelids?
• Which key genetic components are involved in the regulation of metamerism?
• Why are molluscs considered non-metameric compared to other Lophotrochozoans?

Related terms

Segmentation:

The division of an organism’s body into repeated sections or segments.

Setae: Bristle-like structures on annelids that aid in locomotion and sensory functions.

Hox Genes: A group of related genes that determine the basic structure and orientation of an organism's body plan during embryonic development.