Q1: Multiple Choice Questions:
(i) Which one of the following figures represents the age of the earth?
(a) 4.6 million years
(b) 13.7 billion years
(c) 4.6 billion years
(d) 13.7 trillion years
Ans: (c)
(ii) Which one of the following is not related to the formation or modification of the present atmosphere?
(a) Solar winds
(b) Differentiation
(c) Degassing
(d) Photosynthesis
Ans: (b)
(iii) Life on the earth appeared around how many years before the present?
(a) 13.7 billion
(b) 3.8 million
(c) 4.6 billion
(d) 3.8 billion
Ans: (d)
Q2: Answer the following questions in about 30 words.
(i) What is meant by the process of differentiation?
Ans: The process by which earth forming material got separated into different layers is called differentiation. Starting from the surface to the central parts, we have layers like the crust, mantle, outer core and inner core. From the crust to the core, the density of the material increases.
(ii) What was the nature of the earth surface initially?
Ans: The planet earth initially was a barren, rocky and hot object with a thin atmosphere of hydrogen and helium. This is far from the present day picture of the earth.
(iii) What were the gases which initially formed the earth’s atmosphere?
Ans: Hydrogen and helium were the gases which intially formed the earth's atmosphere. The early atmosphere, with hydrogen and helium, is supposed to have been stripped off as a result of the solar winds. During the cooling of the earth, gases and water vapour were released from the interior solid earth. This started the evolution of the present atmosphere.
Q3: Answer the following questions in about 150 words.
(i) Write an explanatory note on the ‘Big Bang Theory’.
Ans:
The 'Big Bang Theory' also known as expanding universe hypothesis. Edwin Hubble, in 1920, provided evidence that the universe is expanding. The distance between the galaxies is also found to be increasing and thereby, the universe is considered to be expanding.
Various stages in the development of the universe according to Big Bang Theory are:
(ii) List the stages in the evolution of the earth and explain each stage in brief.
Ans:
Stage I: The earth was mostly in a volatile state during its primordial stage. Due to gradual increase in density the temperature inside has increased. As a result, the material inside started getting separated depending on their densities.
Stage II: The early atmosphere, with hydrogen and helium, is supposed to have been stripped off as a result of the solar winds. During the cooling of the earth, gases and water vapour were released from the interior solid earth which started the evolution of the present atmosphere.
Stage III: The last phase in the evolution of the earth relates to the origin and evolution of life.
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1. How did the Earth originate according to scientific theories? |
2. What is the process of Earth's evolution over time? |
3. How do scientists study the origin and evolution of the Earth? |
4. What role did the early atmosphere play in shaping the Earth's evolution? |
5. How has the study of the Earth's origin and evolution helped us understand planetary systems beyond our own? |
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