Question

Secondary radial symmetry is found in
A. Cnidaria
B. Jellyfish
C. Echinodermata
D. Hemichordata

Answer 1

Symmetry in a biological organism is the balanced distribution of the duplicated parts of the body and shapes. Most of the living organisms are known to exhibit symmetry in their body plans though some organisms are exceptions such as sponges and placozoans.

Complete answer:
The arrangement of parts of the body and its shapes that are arranged in a duplicated or balanced manner is known as symmetry. It is the repetition of the parts in an organism in some kind of orderly and suitable manner. The symmetry of the organism is generally of two major types which are radial and bilateral symmetry. In radial symmetry both parts are arranged around a central axis while in bilateral symmetry, the body contains a single plane of symmetry and can be divided into exact halves.
Secondary radial symmetry is the presence of both radial and bilateral symmetry in the life period of an organism. The animals of the phylum Echinodermata exhibit secondary radial symmetry. In them, the adults display radial symmetry but the larval stages show bilateral symmetry. They show both the two types of symmetry. The evolution of secondary radial symmetry in echinoderms are known to arise from bilaterally symmetrical ancestors.
The radial symmetry is the presence of arrangement of the body parts around a central axis. In radial symmetry, the body of the organism cannot be divided into equal parts if cut in any plain. The animals with radial symmetry possess a top and bottom portion which is known as the oral and the abdominal sides. This type of symmetry is very common in the Cnidaria and Ctenophora.
Jelly fishes are known to have radial symmetry. The body of the jellyfish can be distinguished only in the upper part or oral surface and lower part or the abdominal surfaces.
The hemichordates are represented by organisms such as the acorn worms and they are solitary worms like organisms with a proboscis and collar. They exhibit bilateral symmetry.

Note: The secondary radial symmetry is the condition where both the radial and bilateral symmetry conditions are exhibited by an organism in different stages of life. This feature is especially found in the phylum Echinodermata.