Which symmetry type is common in cnidarians and echinoderms?

Which symmetry type is common in cnidarians and echinoderms?

• A. Polyp
• B. Porifera
• C. Reptilia
• D. Radial Symmetry

Answer: (D)

Radial symmetry is a body plan where parts are arranged around a central axis, so the organism can interact with its environment from any direction. In cnidarians, like jellyfish and sea anemones, the body is organized around the mouth with tentacles radiating outward, showing a circular symmetry. In echinoderms, adults display pentaradial symmetry—five repeating sections around a central axis (though their larvae are bilaterally symmetric)—which is still a radial pattern. This shared arrangement around a central point is why radial symmetry is the correct concept for both groups. The other options aren’t symmetry types: a polyp is a cnidarian life stage, Porifera refers to sponges with variable or no definite symmetry, and Reptilia is a vertebrate group with bilateral symmetry.

Radial symmetry is a body plan where parts are arranged around a central axis, so the organism can interact with its environment from any direction. In cnidarians, like jellyfish and sea anemones, the body is organized around the mouth with tentacles radiating outward, showing a circular symmetry. In echinoderms, adults display pentaradial symmetry—five repeating sections around a central axis (though their larvae are bilaterally symmetric)—which is still a radial pattern. This shared arrangement around a central point is why radial symmetry is the correct concept for both groups. The other options aren’t symmetry types: a polyp is a cnidarian life stage, Porifera refers to sponges with variable or no definite symmetry, and Reptilia is a vertebrate group with bilateral symmetry.