Question

Radial symmetry is shown by
a. Arthropoda
b. Bryozoa
c. Chordata
d. Cnidaria
e. Mollusca

Answer 1

Hint: This phylum's body plan is circular in body plan, and every cut through the animal's middle leaves two identical halves. So, make these species very distinct from the species that existed before them.

Complete answer:
> Option A is incorrect. Arthropods are distinguished by triploblastic, joined limbs that can be found in all habitat types – grass, water, and soil. The body is segmented into three regions-head, thorax and abdomen and chitin cuticle, also mineralized with calcium carbonate. The body plan for the arthropod consists of segments, each with a pair of appendices.

> Option B is incorrect. Bryozoa (moss species) also known as Polyzoa, Ectoprocta or generally known phylum of invertebrate marine animals. Bilaterally, they are symmetrical. · Body consists of more than two layers of cells, tissues and organs. A real coelom to the body cavity. They are philtre feeders which use a retractable lophophore, a "crown" of tentacles lined with cilia, to sieve food particles out of the water.

> Option C is incorrect. Chordates have a notochord, a dorsal nerve line, pharyngeal slits, and a post-anal tail: this phylum is characterised by these four anatomical traits. There are also bilateral symmetric chordates with a body cavity, metameric segmentation, and circulatory system.
> Option D is correct. Cnidaria is a phylum comprising species such as a hydra, jellyfish, marine anemones etc. The body has a gastrovascular cavity, and a diploblastic body wall. They are radially symmetrical animals (which is symmetry around a central axis, so any plane that includes the main axis will divide the organism into similar halves).

> Option E is incorrect. A mollusc's body plan typically consists of a head area, a muscular foot and a visceral mass of internal organs sometimes enclosed in a dorsal shell. Each class has some variation on the fundamental plan. The gastropod body structure is very similar to the mollusc base body plan.

Hence, The correct answer is option (D).

Note: Cnidarians have two distinct planes of the body, medusa and polyp. All of them have a jelly-like mesoglea between two membrane layers. In this phylum, species exhibit two distinct morphological planes of the body: polyp or "stalk" and medusa or "bell."