Question

Cnidaria is characterised by
A. Nematoblasts
B. Coelenteron
C. Tissue level of organization
D. All of the above

Answer 1

Hint: Cnidaria are diploblastic organisms. They have two main cell layers, in other words. Epithelia, which are often one cell thick, are formed by the two main cell layers of cnidarians and attached to a fibrous basement membrane, which they secrete.

Complete answer: Cnidaria is a group of sessile or free-swimming animals characterized by primary radial symmetry, often modified as biradial or quad radial, supplied with unique cnidae (stinging capsules). The basic structure is sac-like, acting both as the mouth and the anus, with a single terminal opening. Cnidaria has 3 layers of tissues; an outer protective layer called the epidermis, a middle layer called mesoglea, and an inner layer called the gastrodermis. They regulate the function of digestion. Using tentacles that are incorporated with stinging nematocysts Cnidarians eat. They also have a diploblastic or two-level tissue organization. Cnidarians have a real coelom or coelenteron. Their specialized stinging structures or nematocysts/nematoblasts assist in the defence. At the tissue level of organization, Cnidarians are said to be the simplest organisms; their cells are organized into true tissues. Cnidarians are simply bags constructed from two layers of cells. The cnidocytes, the stinging cells that are typical of the phylum, are in the outer ectoderm or epidermis.
Hence, the correct answer is option D.

Note: Cnidarians are very important in the open ocean as predators. They assist a lot in the smooth functioning and operation of the ocean ecosystem's food chain and food network. Coral reefs are known to be one of the most abundant and important habitats on earth.