1. What are corals?
Ans. Corals are the anthozoan polyps of Phylum Cnidaria, which are capable of secreting calcareous materials or a horny organic material that form a hard external or internal skeleton.
2. What is Corralite and Corralum?
Ans. The skeleton formed by a solitary polyp is called Corralite, while the skeleton of entire colony is called corallum.
3. What is solitary Coral? Give two generic examples.
Ans. When the single polyp with its simple corallite lives separately, it is called solitary Coral.
e.g. Fungia (Mushroom Coral), Flabellum.
4. What is Colonial Coral? Give four generic examples.
Ans. When several polyps form a colony and are interconnected with each other, it is called colonial Coral.
e.g. Meandrina (Brain Coral), Oculina (eyed Coral), Tubipora (Organ-pipe Coral), Gorgonia (Sea fan).
5. What are hermatypic Corals? Give examples.
Ans. Hermatypic Corals are those Corals which have symbiotic algae in their gastodermis and partipate in building Coral reefs.
e.g., most of the Corals like Acropora, Meandrina, Oculina, Tubipora etc.
6. What are Coral reefs?
Ans. Coral reefs are Coral islands formed of Coral skeleton, together with shells or skeletons of foraminifera, molluscs, echinoderms, annelids etc. cemented together into a hard rock by encrusting algae or sponges. Madreporarian Corals are the main contributor to reef formation.
7. Comment on the distribution of Coral reefs?
Ans. At latitude 23°27′ North and South of the Equator are the Tropic of Cancer and Tropic of Capricon. They mark the position where the sun shines directly overhead in the midsummer. In this area are found most of the corals and coral reefs of the world. Hence, coral reefs are the features of tropical and subtropical seas, where the average minimum water water temperature is not less than 20°C. Existing reef’s are restricted to the Caribbean sea. Indian ocean and tropical Pacific. Reefs are conspicuously absent from much of the Atlantic.
8. What are the conditions necessary for growth of Reef Corals?
Ans. Following are environmental demands for growth of Reef Corals-
(i) Water depth and light penetration:
Reef Corals grow best in shallow water, i.e., from surface down to depth of 6 fathoms. This is essential for effective light penetration for photosynthesis of symbiotic algae.
(ii) Water temperature:
Reef corals grow in the range of 20°C-28°C, with best at 23°-25°C.
(iii) Clear, low turbid water.
(iv) Hard sea bottom.
9. How many types of Coral reef are there?
Ans. There are three main types of reef: Fringing reef, Barrier reef and Atoll. Besides, there are other two types: Table reef or platform reef and patch reef.
10. What is fringing reef? Give example.
Ans. Such reef project seaward directly from the shore, extending a few feet to one-forth mile out. It surrounds the islands or continents following its curves and turns. It is often broken here and there by channels of poor depth. The intervening water between land and reef is a narrow, shallow channel. In Indian ocean, such reefs are found around southern India, Sri Lanka, Andamans and Malay Archipelago.
11. What is barrier reef? Give examples.
Ans. It is somewhat similar to fringing reef but the reef platform is separated from the land mass by a lagoon channel which is about half a mile to 30 miles or oven 90 miles wide and has a depth of 60-360 feet.
e.g. The Great Barrier Reef of Australia is the longest barrier reef of the world, extending over 1200 miles along the Australian north-east coast.
12. What is Atoll? Give examples.
Ans. Such reef lies on the top of submerged volcano in the open sea. It is often circular oval or horse-shoe shaped with a central lagoon of less than a mile to 40 or 50 miles across and 20-35 fathoms depth.
13. What are the hermatypic and ahermatypic corals?
Ans. The true corals belong to the order Scleractinia of subclass Hexacorralia under class Anthozoa. These corals may be reef building or hermatypic and not reef building or ahermatypic. Most hermatypic corals are restricted to clear, warm waters. The example of ahermatypic coral is solitary corals like Agaricia, Fungia etc.
14. State about the coral reef of Indian water with a note on Indian coral species.
Ans. Several islands in the Gulf of Mannar and near about such as the Krusadi group of islands are coral islands with sand stone forming the base rock. Reddiah (1970) gave an account on the Appa island and its fringing reef in the Gulf of Mannar. Dominant corals of the areas are Porites, Montipora, Acropora and Madrepora etc.
15. What is economic importance of coral reef?
Ans. (i) Coral reefs serve as habitats for a large variety of organisms.
(ii) Reefs determine a relative chronology for geologic deposits and a time scale of events.
(iii) Jwellary and ornaments.
(iv) Ancient reefs are now considered important reservoirs of petroleum.