Coelenterates Online Quiz | Invertebrates

Quiz Answer Key and Fun Facts

1. The Kingdom Animalia (Animal Kingdom) to which coelenterates belong has been divided into various phyla (singular: phylum) in which animals with some common ancestry are grouped together. For example, there is Phylum Porifera for sponges, Phylum Annelida for segmented worms and so on. As you might have guessed, there is a separate phylum which includes almost all coelenterates. What is the name of this phylum?

Answer: Phylum Cnidaria

Phylum Platyhelminthes includes flatworms such as tapeworms and liver flukes, Arthropoda is the largest phylum, which includes animals with jointed or segmented feet, such as cockroaches and lobsters. Phylum Chordata is characterised by animals that possess a notochord, which is developed into a vertebral column in higher chordates. Human beings belong to this phylum.

Phylum Cnidaria (sometimes called Phylum Coelenterata) contains almost all of the world's coelenterates. Many organisms in this phylum, such as jellyfish, have stinging cells called cnidocytes, from which the phylum name 'cnidaria' is derived.

2. Coelenterates exist in two forms or zooids- polyps and medusae. Polyps occur mostly in colonies, and attach themselves to rocks or debris on the sea-bed, while almost all medusae are free-living and can swim. Do reef-building corals occur in the polyp form?

Answer: Yes

Coral polyps are sessile and live in colonies and flourish in warm, shallow and clear waters. They are responsible for the formation of the Great Barrier Reef off the coast of Australia and for the formation of many islands. Medusae, on the other hand, are free living, and include coelenterates such as jellyfish and hydra.

A few coelenterates lead dual lives; for a part of their lives they exist as polyps and the rest of their lives as medusae.

3. Among the metazoa (multicellular organisms) in the Kingdom Animalia, above which group do coelenterates rank in complexity?

Answer: sponges

Sponges (of the Phylum Porifera) are simpler than coelenterates. Leaving out sponges, coelenterates are the simplest multicellular animals (remember, protozoa are unicellular, i.e. single-celled). The cells of coelenterates are organised into tissues, a few of which make up simple organs. There is no body cavity (coelom) or organ-system.

4. Coelenterates are very simple organisms, made up of different tissues and a few simple organs. What is the name given to the system of chambers or tubes within a coelenterate?

Answer: coelenteron

A coelenteron is what defines coelenterates. It is used both as a mouth, through which the coelenterate ingests the food, and as an anus. It is a 'gastrovascular cavity'. Cnidoblasts, cnidocytes and nematocysts are the special stinging cells on the tentacles of many coelenterates.

5. Here is the name of a coelenterate that has been scrambled: EENAASNMEO. Using these letters, construct the coelenterate!

Answer: sea anemone

Sea anemones are examples of coelenterates that exist in polyp form. One end of them is attached to either rocks or corals on the sea bed and on the other end they are armed with numerous tentacles armed with nematocytes, which are stinging cells that paralyze and capture their pray which they can later ingest.

A type of sea anemone found off the coast of Newfoundland in Canada engages in a symbiotic relationship with hermit crabs under the water. The sea anemones increase the hermit crab's defensive capabilities (remember, they've got those special stinging cells), while the crab supplies the sea anemone with food.

6. The phylum to which coelenterates belong is made up of the Class Hydrozoa (primarily polyps), Class Anthozoa (polyps only), Class Cubozoa (box-like coelenterates, considered by some to be a part of Class Scyphozoa) and Class Scyphozoa (primarily medusae). To which class do sea wasps, one of the greatest hazards to swimmers, belong?

Answer: Class Cubozoa

The Class Cubozoa includes box jellyfish, and one major characteristics of these coelenterates are their particularly potent and deadly stinging cells. They are medusae (free living), and do not intentionally sting the humans. They pose a serious hazard for swimmers on many beaches. An example of a cubozoid is the sea wasp, which is said to be the world's deadliest jellyfish.

7. Coelenterates are diploblastic, i.e., they possess two basic layers of tissues. The outer layer is know as the ectoderm, and the inner layer is know as the endoderm. Between these layers there is a jelly-like non-cellular substance. What is this substance called?

Answer: mesoglea

While epidermis is just another name for the ectoderm, gastrodermis is another name for the endoderm. Between these layers lies the jelly-like mesoglea, which forms the bulk of most jellyfish; hence their name.

8. This is among the simplest of coelenterates and belongs to the Class Hydrozoa. It is among the simplest-structured multicellular organism and is used in many elementary biology classes. It has six to ten tentacles surrounding the mouth which it uses to capture food. It moves either by gliding on its foot or by somersaulting. It reproduces by forming buds. Two species of this coelenterate are commonly found, one brownish-grey in colour and one green in colour. Which coelenterate am I talking about?

Answer: hydra

The green colour of Chlorohydra viridissima is due to a symbiotic relation with an alga that lives in its body cells. Hydras show remarkable powers of regeneration, i.e., when cut into fairly large pieces, each piece grows into a complete individual. Small pieces of hydra placed in close contact with each other together grow to form a complete individual hydra.

9. Which of the following is NOT a coelenterate?

Answer: Common Pacific Squid

While corals and Portuguese man-of-war (Physalia physalis) are coelenterates belonging to the Phylum Cnidaria, the Common Pacific Squid (Loligo opalescens) belongs to the Phylum Mollusca, which includes molluscs, which are soft-bodied animals that usually have a hard outer covering.

10. Which class of coelenterates has the greatest number of species?

Answer: Class Anthozoa

There are approximately 9200 species in the Phylum Cnidaria. The following table shows approximately how many species are found in each of the four classes:
Class Anthozoa - 6000
Class Cubozoa - 20
Class Hydrozoa - 3000
Class Scyphozoa - 200

As you can see, Class Anthozoa (which includes corals, sea anemones, etc.) clearly outnumbers all the other classes in terms of number of species.

Source: Author achernar

This quiz was reviewed by FunTrivia editor crisw before going online.
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Coelenterates Trivia Quiz

This wide, wide world contains an incredible variety of animals. Among these are the not-so-well-known coelenterates. Some of you may ask- what in the world is a 'coelenterate'? Take this quiz and learn something new!

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