Which of the following has radial symmetry?

Option 3 : Echinus (Sea urchin)

The correct answer is Echinus (Sea urchin).

Concept:

• The animal kingdom is divided into many sub-groups called phyla.
• The basis for categorization includes:
  • Arrangement of cells 
  • Body symmetry
  • Nature of coelom (body cavity)
  • Patterns of digestive, circulatory, or reproductive systems

Explanation:

Body Symmetry:

• There are 3 types of symmetry: Bilateral, Radial, and Asymmetrical.
• Bilateral Symmetry:
  • Animals, whose bodies can be divided into left and right halves, are said to be bilaterally symmetrical.
  • For example Platyhelminthes, Annelida, Arthropoda, Chordata, etc. 
• Radial Symmetry:
  • Animals whose bodies can be divided into two equal halves from any plane passing through the center of the body are said to be radially symmetrical.
  • For example Coelenterates, Echinoderms, and Ctenophores.
• Asymmetrical:
  • ​Few animals cannot be divided into two equivalent parts along with any plane going through the central point of the organism. They are said to be asymmetrical. 
  • For example Sponges.

Thus, Echinus has radial symmetry.