Radial symmetry

Definition

Radial symmetry is a body plan in which any longitudinal cut through the central axis results in identical halves. It is commonly found in organisms like jellyfish, sea anemones, and starfish.

5 Must Know Facts For Your Next Test

1. Most radial symmetric animals are sessile or planktonic, meaning they are either stationary or float freely.
2. This type of symmetry allows for equal interaction with the environment from all sides.
3. Radial symmetry is typically associated with simpler organisms compared to bilateral symmetry.
4. It often involves a central mouth surrounded by tentacles or other structures for feeding.
5. Organisms with radial symmetry usually lack a head region, unlike those with bilateral symmetry.

Review Questions

• What advantage does radial symmetry provide to sessile or planktonic organisms?
• How does radial symmetry differ from bilateral symmetry in terms of complexity?
• Why do radially symmetric organisms typically lack a head region?

Related terms

Bilateral Symmetry: A body plan where only one longitudinal cut through the central axis divides the organism into mirror-image halves.

Sessile: An organism that remains attached to a surface for most of its life and does not move.

Planktonic: Describes small organisms that float or drift in water currents, often including many radially symmetric species.