Which one of the following is the oldest era in Geological History determining the age of various rock types?
- A.Precambrian
- B.Mesozoic
- C.Cenozoic
- D.Paleozoic
Correct answer
Explanation
The correct answer is A, Precambrian. The Precambrian covers all of Earth's history from its formation about 4.6 billion years ago to the start of the Cambrian about 541 million years ago.
The Precambrian takes up nearly 88% of geological time. Its rocks include the oldest on Earth, and in India the Archaean rocks of the Peninsular plateau, such as gneisses and schists, and the Dharwar system belong to it. Life in this time was mostly simple and single-celled. After it come three eras in order: the Paleozoic, the age of early life, fishes and the first land plants; the Mesozoic, the age of reptiles and dinosaurs; and the Cenozoic, the age of mammals, which continues today.
B is wrong because the Mesozoic, about 252 to 66 million years ago, came after the Paleozoic.
C is wrong because the Cenozoic is the youngest era and includes the present.
D is wrong because the Paleozoic began only after the Precambrian ended.
Exam tip: oldest to youngest, Precambrian, Paleozoic, Mesozoic, Cenozoic.
Practice Questions
View allConsider the following statements:
1. In the tropical zone, the western sections of the oceans are warmer than the eastern sections owing to the influence of trade winds.
2. In the temperate zone, westerlies make the eastern sections of oceans warmer than the western sections.
Which of the statements given above is/are correct?
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
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The prevailing winds push warm surface water west in the tropics and east in the middle latitudes. In the tropics the trade winds blow from east to west.
Read the full explanation →Consider the following statements:
Statement-I: The soil in tropical rain forests is rich in nutrients.
Statement-II: The high temperature and moisture of tropical rain forests cause dead organic matter in the soil to decompose quickly.
Which one of the following is correct in respect of the above statements?
- A.Both Statement-I and Statement-II are correct and Statement-II is the correct explanation for Statement-I
- B.Both Statement-I and Statement-II are correct and Statement-II is not the correct explanation for Statement-I
- C.Statement-I is correct but Statement-II is incorrect
- D.Statement-I is incorrect but Statement-II is correct
Show answer
Rain forest soils are poor in nutrients, even though dead matter decomposes very fast there. In the hot, wet climate of tropical rain forests, fallen leaves and wood are broken down by fungi, bacteria and insects within weeks.
Read the full explanation →Consider the following statements about Particularly Vulnerable Tribal Groups (PVTGs) in India:
1. PVTGs reside in 18 States and one Union Territory.
2. A stagnant or declining population is one of the criteria for determining PVTG status.
3. There are 95 PVTGs officially notified in the country so far.
4. Irular and Konda Reddi tribes are included in the list of PVTGs.
Which of the statements given above are correct?
- A.1, 2 and 3
- B.2, 3 and 4
- C.1, 2 and 4
- D.1, 3 and 4
Show answer
Statement 3 is wrong: 75 PVTGs have been notified in India, not 95. The category was created in 1973, following the Dhebar Commission, as 'Primitive Tribal Groups' and renamed PVTGs in 2006.
Read the full explanation →Among the following, which one is the least water-efficient crop?
- A.Sugarcane
- B.Sunflower
- C.Pearl millet
- D.Red gram
Show answer
Sugarcane needs far more water to grow than the other three crops, so it is the least water-efficient. Sugarcane stays in the field for 12 to 18 months and needs roughly 1,500 to 2,500 mm of water over its life, often supplied by heavy irrigation.
Read the full explanation →With reference to the Earth's atmosphere, which one of the following statements is correct?
- A.The total amount of insolation received at the equator is roughly about 10 times of that received at the poles.
- B.Infrared rays constitute roughly two-thirds of insolation.
- C.Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere.
- D.Infrared waves are a part of visible spectrum of electromagnetic waves of solar radiation.
Show answer
Infrared radiation is strongly absorbed by water vapour, and most water vapour lies in the lowest few kilometres of the atmosphere.
Read the full explanation →