NIOS Class 10 Science and Technology Chapter20: HISTORY OF LIFE ON EARTH– Chapter-wise Important Questions and Answers

NIOS Class 10 Science and Technology Chapter20: HISTORY OF LIFE ON EARTH | MCQs, Short & Long Answer Questions | 20. HISTORY OF LIFE ON EARTH

Chapter20: HISTORY OF LIFE ON EARTH

INTEXT QUESTIONS 20.1

1. When did the earth come into existence?

Answer: Earth formed about 4.54 to 5 billion years ago from gas and dust around the young Sun.

2. Why did life not exist on primitive earth?

Answer: Life did not exist on primitive Earth because it was too hot, and the atmosphere contained only certain gases with a reducing atmosphere, which was not suitable for life.

3. What are fossils?

Answer: Fossils are the remains of organisms that lived in the past and are preserved in rocks.

4. What is meant by Cambrain explosion?

Answer: The Cambrian explosion was the time about 600 million years ago when there was a sudden formation of different groups of invertebrates on Earth.

5. From the geological time scale, find out the time in million years ago(mya) when:

(i) dinosaurs became extinct ______________

(ii) human evolution began ______________

(iii) flowering plants became dominant on earth ______________

Answer: (i) Dinosaurs became extinct — 144–65 mya
(ii) Human evolution began — 1.5–2 million years ago (mya)
(iii) Flowering plants became dominant on Earth — 57–34 mya

INTEXT QUESTIONS 20.2

1. Who is Charles Darwin? Name his famous book on natural selection.

Answer: Charles Darwin was an English scientist who explained the theory of evolution by natural selection. His famous book on natural selection is On the Origin of Species.

2. Mention his two major contributions.

Answer: The two major contributions of Charles Darwin are:

(i) all organisms related through ancestry

(ii) Mechanism of evolution is Natural Selection.

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