GC Leong Test: Island And Coral Reefs


10 Questions MCQ Test Geography for UPSC CSE | GC Leong Test: Island And Coral Reefs


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QUESTION: 1

British Isles, the Balearic Islands of the Mediterranean and also those of the Aegean Sea are the example of:

Solution: Archipelagoes or island groups. These comprise groups of islands of varying sizes and shapes, such as the British Isles, the Balearic Islands of the Mediterranean, and those of the Aegean Sea.

QUESTION: 2

Consider the following statements about the Oceanic Islands. 

1. These are normally small and are located in the midst of oceans 

2. Their former connection with the neighbouring mainland can be traced from the similar physical structure 

3. Remoteness from the major trading centres of the world is a feature of these Islands 

Which of these statements is/are correct?

Solution:  

Oceanic islands: 

  • These islands are normally small and are located in the midst of oceans. They have no connection with the mainland, which may be hundreds or thousands of miles away. 

  • They have flora and fauna unrelated to those of the continents. The Galapagos Islands have many unique species of animals.

  • Due to their remoteness from the world's major trading centres, most of the oceanic islands are very sparsely populated.

QUESTION: 3

Consider the following statements about the Coral Islands. 

1. Unlike the volcanic islands, the coral islands are very much lower and emerge just above the water surface 

2. Mauritius and Reunion Islands of the Indian Ocean are the examples 

Which of these statements is/are correct?

Solution:  

Coral islands. Unlike the volcanic islands, the coral islands are much lower and emerge just above the water surface. These islands, built up by coral animals of various species, are found both near the mainland and in the midst of oceans.

QUESTION: 4

Consider the following statements by Coral Polyps. 

1. They secrete calcium carbonate with their tiny cells 

2. Under favourable conditions, they grow in great profusion just below the water level 

3. Each polyp resides in a tiny cup of Coral and helps to form coral reefs 

Which of these statements is/are correct?

Solution:  

Coral Reefs: 

  • Many kinds of coral animals and marine organisms such as coral polyps, calcareous algae, shell-forming creatures, and lime-secreting plants live in large colonies in tropical seas. 

  • Though they are very tiny creatures, their ability to secrete calcium carbonate within their tiny cells has given rise to a particular marine landform type. They exist in numerous species of many forms, colours and shapes.

  • Under favourable conditions, they grow in great profusion just below the water level. Taking coral animals as a whole, the polyps are the most abundant and also the most important.

QUESTION: 5

Which of these are correctly matched? 

1. Precious corals - Pacific Ocean 

2. Red coral - Mediterranean 

Choose from the following options

Solution:  

There are also non-reef- building species such as the "precious corals' of the Pacific Ocean and the 'red coral of the Mediterranean which may survive in the colder and even the deeper waters. As a rule, they thrive well only in the warmer tropical seas.

QUESTION: 6

Assertion (A): Coral reefs are generally absent on the Western coasts of continents 

Reason (R): Coral reefs do not flourish where there are cold currents 

Choose from the following options.

Solution:  
  • The water temperature must not fall 68°F. (20°C.). 

  • This virtually limits the areal distribution of corals to the tropical, and subtropical zones. 

  • Again they will not flourish where there are cold currents because of the cold water's upwelling from the depths that cools the warm surface water. 

  • This explains why coral reefs are generally absent on the western coasts of continents. 

  • On the other hand, the warming effect of the warm currents, e.g. the Gulf Stream, means that corals are found far to the north of the West Indies in the Atlantic Ocean. 

  • The Pacific and the Indian Oceans, however, have the most numerous coral reefs

QUESTION: 7

Assertion (A): The depth of water exceeding 180 feet is not suitable for the coral reefs 

Reason (R): Sunlight is too faint for photosynthesis to take Place Beyond this depth 

Choose from the following options.

Solution:  
  • The water depth should not exceed 30 fathoms or 180 feet, because beyond this depth, sunlight is too faint for photosynthesis to occur. 

  • This is essential for the survival of the microscopic algae, on which the coral polyps depend. Shallow water of less than 100 feet is ideal. But there should always be plenty of water as polyps cannot survive for too long out of water.

QUESTION: 8

Which of the following conditions are suitable for coral reefs? 

1. The water should be Saltish 

2. The water should be free from sediment 

3. The coasts should be silty 

Consider the following statements.

Solution:

Coral animals and marine organisms like coral polyps which live in large colonies in tropical seas have the ability to secrete calcium carbonate within their tiny cells. Polyps reside in tiny cups of coral and help to form coral reefs. Coral reefs begin to form when free swimming coral larvae attach to submerged rocks or other surfaces.
The conditions necessary for the formation of coral reefs are as follows:
1. Water temperature must not fall below 20 degree Celsius.
2. Depth of water should not exceed 180 feet because beyond this sunlight is too faint for photosynthesis to take place.
3. The water should not be saltish and free from sediment. They survive best in moving ocean water away from silty coasts or muddy mouths of streams.

QUESTION: 9

Consider the following statements about fringing reefs. 

1. It is a coralline platform lying close to the shore extending outwards from the mainland 

2. It is sometimes separated from the shore by a shallow lagoon 

3. It is widest when fringing a protruding headland but completely absent when facing the mouth of a stream

Which of these statements is/are correct?

Solution: Fringing reefs: 
  • A fringing reef is a coralline platform lying close to the shore extending outwards from the mainland. 

  • It is sometimes separated from the shore by a shallow lagoon. 

  • It is widest when fringing a protruding headland but completely absent when facing the mouth of a stream. 

  • The outer edge grows rapidly because of the splashing waves that continuously renew the supply of fresh food.

QUESTION: 10

Consider the following statements. 
1. Atolls are similar to fringing reefs except that they are circular in shape, enclosing a shallow lagoon without any land in the centre. 
2. The encircling ring is usually broken in a few places to allow the free flow of water 

Which of these statements is/are correct?

Solution:

 

Atolls: 

  • Atolls are similar to barrier reefs except for circular shape, enclosing a shallow lagoon without any land in the centre. 

  • The encircling ring is usually broken in a few places to allow the free flow of water. On the inside of the reefs, sand and limestone debris collect and palm trees like coconuts may grow.

  • Such palm trees thrive well in the lagoon's brackish water; nuts fall into the water and are distributed by floating from one coral island to another. 

  • The calm waters are useful for fishing and canoeing, Some of the large atolls, e.g. Suvadiva in the Maldives, west of Ceylon, have a lagoon over 40 miles across. A number of them provide essential air bases for trans-Pacific aircraft.

 

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