Phylum Coelenterata (Cnidaria) Quiz
Coelenterates — better known today as cnidarians — mark a decisive step in animal evolution: the appearance of a true tissue level of organisation. This quiz tests the diagnostic features that define the phylum, from the stinging cnidoblasts to the two body forms, polyp and medusa.
What you will practise
- Habitat and radial symmetry of cnidarians
- Cnidoblasts, cnidocytes and nematocysts — structure and uses
- Diploblastic, tissue-level body plan and the gastro-vascular cavity
- Polyp versus medusa, and metagenesis in Obelia
- Recognising genera such as Physalia, Adamsia, Gorgonia and Meandrina
Work through all 15 questions carefully — each explanation reinforces the concept behind the answer.
Q1. The name Cnidaria is derived from which structure?
The name Cnidaria comes from cnidoblasts (also called cnidocytes), the stinging cells that contain nematocysts.
Q2. Cnidarians are best described as:
The phylum is defined as aquatic, mostly marine, sessile or free-swimming, radially symmetrical animals.
Q3. The stinging capsules contained within cnidoblasts are called:
Cnidoblasts contain stinging capsules known as nematocysts, present on the tentacles and body.
Q4. Cnidoblasts are used for which of the following?
Cnidoblasts serve for anchorage, defence and the capture of prey.
Q5. What level of organisation do cnidarians exhibit?
Cnidarians show a tissue level of organisation, an advance over the cellular level seen in sponges.
Q6. Cnidarians are described as diploblastic because:
Diploblastic means the body is formed from two germ layers, unlike the triploblastic condition of higher phyla.
Q7. The gastro-vascular cavity of a cnidarian is characterised by:
Cnidarians have a central gastro-vascular cavity with a single opening, the mouth, situated on the hypostome.
Q8. Which body form is sessile and cylindrical?
The polyp is the sessile, cylindrical form, as seen in Hydra and Adamsia.
Q9. The medusa form of a cnidarian is:
The medusa is umbrella-shaped and free-swimming, as in Aurelia or jelly fish.
Q10. Metagenesis, or alternation of generations, is exhibited by:
Obelia exists in both polyp and medusa forms, showing metagenesis.
Q11. In metagenesis, which statement is correct?
In metagenesis, polyps produce medusae asexually, while medusae form polyps sexually.
Q12. Which of the following is a polyp-form example given in the lesson?
Adamsia (sea anemone) is cited as a sessile, cylindrical polyp form, like Hydra.
Q13. Physalia is commonly known as:
Physalia is the Portuguese man-of-war, one of the listed examples of Coelenterata.
Q14. Which pair correctly matches the organism with its common name?
Gorgonia is the sea-fan and Meandrina is the brain coral, as listed in the lesson examples.
Q15. The skeleton of corals is composed of:
Some cnidarians, such as corals, have a skeleton composed of calcium carbonate.