Question 1

The stinging cells (cnidoblasts) used for defence and capture of prey are characteristic of:

Accepted Answer

Coelenterata (Cnidaria). Cnidoblasts/cnidocytes bearing nematocysts on the tentacles define the Cnidaria.

Question 2

Ctenophores move using eight external rows of:

Accepted Answer

Ciliary comb plates. Ctenophores (sea walnuts/comb jellies) swim by beating eight rows of ciliated comb plates.

Question 3

The two body forms — a sessile polyp and a free-swimming medusa — occurring in the life cycle of some cnidarians is called:

Accepted Answer

Metagenesis (alternation of generations). Metagenesis: the polyp produces medusae asexually and medusae produce polyps sexually (e.g. Obelia).

Question 4

Both cnidarians and ctenophores share which grade and symmetry?

Accepted Answer

Diploblastic, tissue level, radial symmetry. Both are diploblastic with tissue-level organisation and radial symmetry.

Question 5

Bioluminescence (light emission) is a well-marked feature of:

Accepted Answer

Ctenophores (e.g. Pleurobrachia, Ctenoplana). Ctenophores are noted for bioluminescence; they lack cnidoblasts (a key difference from Cnidaria).

Question 6

Which cnidarian example correctly matches its predominant body form?

Accepted Answer

Adamsia (sea anemone) — polyp; Aurelia (jelly fish) — medusa. Sea anemones/corals are polypoid; jelly fish are medusoid; colonial forms (Physalia) show both.

Question 7

The hard skeleton of reef-building corals (e.g. Meandrina) is composed of:

Accepted Answer

Calcium carbonate. Corals secrete a hard external skeleton of calcium carbonate (calcareous), which over time builds coral reefs.

Question 8

Ctenophores are commonly known as:

Accepted Answer

Sea walnuts or comb jellies. Ctenophora are called sea walnuts or comb jellies. Sea anemones, jelly fishes and sea pens are all cnidarians (Coelenterata).

Question 9

Digestion in cnidarians (coelenterates) is:

Accepted Answer

Both extracellular and intracellular. In cnidarians food is first broken down in the gastrovascular cavity (extracellular) and then taken up by cells for intracellular digestion, so both occur.

Question 10

Assertion (A): Ctenophores are exclusively marine animals. Reason (R): Ctenophores show the property of bioluminescence. Choose the correct option.

Accepted Answer

Both A and R are true but R is not the correct explanation of A. Both statements are individually true, but being exclusively marine is not caused by bioluminescence, so R is not the correct explanation of A.

Question 11

Match the cnidarian with its common name — (i) Adamsia, (ii) Physalia, (iii) Pennatula, (iv) Aurelia:

Accepted Answer

i-sea anemone, ii-Portuguese man-of-war, iii-sea-pen, iv-jelly fish. Adamsia is a sea anemone, Physalia the Portuguese man-of-war, Pennatula a sea-pen and Aurelia the common jelly fish.

Question 12

Which of the following statements correctly distinguishes ctenophores from cnidarians?

Accepted Answer

Ctenophores lack cnidoblasts and capture prey using colloblasts, whereas cnidarians possess cnidoblasts. Ctenophores have no stinging cnidoblasts; they use adhesive colloblasts (lasso cells) to catch prey, unlike cnidarians which possess cnidoblasts. Both groups are diploblastic and radially symmetrical.

Question 13

A marine animal is radially symmetrical, diploblastic, has a tissue level of organisation and bears stinging cnidoblasts on its tentacles. To which phylum does it belong?

Accepted Answer

Coelenterata (Cnidaria). Cnidoblasts (with nematocysts) on the tentacles, together with a diploblastic, radially symmetrical, tissue-level body, are the defining marks of phylum Coelenterata (Cnidaria).

Question 14

A jelly-like marine animal bearing eight external rows of ciliated plates used for swimming is placed in which phylum?

Accepted Answer

Ctenophora. Eight external rows of ciliated comb plates for locomotion are the diagnostic feature of phylum Ctenophora (comb jellies).

Question 15

The name "Cnidaria" is derived from the presence of a special type of cell called the:

Accepted Answer

cnidoblast (cnidocyte). The name Cnidaria comes from cnidoblasts (cnidocytes), the cells that contain the stinging capsules (nematocysts).

Question 16

The sessile, cylindrical body form of a cnidarian such as Hydra is called a:

Accepted Answer

polyp. The polyp is the sessile, cylindrical body form of cnidarians (e.g. Hydra, Adamsia); the medusa is the free-swimming umbrella form.

Question 17

The umbrella-shaped, free-swimming body form of a cnidarian such as Aurelia is called a:

Accepted Answer

medusa. The medusa is the umbrella-shaped, free-swimming form (e.g. Aurelia, the jellyfish); the polyp is the sessile cylindrical form.

Question 18

Aurelia is commonly known as the:

Accepted Answer

jellyfish. Aurelia is the jellyfish, the classic free-swimming medusa form of a cnidarian.

Question 19

Physalia is commonly known as the:

Accepted Answer

Portuguese man-of-war. Physalia is the Portuguese man-of-war, a cnidarian example given in NCERT.

Question 20

Adamsia is commonly known as the:

Accepted Answer

sea anemone. Adamsia is the sea anemone, a sessile polyp form of cnidarian.

Coelenterata & Ctenophora — NEET Biology MCQs with Solutions

Questions with solutions