NIOS Class 10 Science and Technology Chapter 20 History of Life on Earth Solutions to each chapter is provided in the list so that you can easily browse through different chapters NIOS Class 10 Science and Technology Chapter 20 History of Life on Earth and select need one. NIOS Class 10 Science and Technology Chapter 20 History of Life on Earth Question Answers Download PDF. NIOS Study Material of Class 10 Science and Technology Notes Paper 212.
NIOS Class 10 Science and Technology Chapter 20 History of Life on Earth
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History of Life on Earth
Chapter: 20
INTEXT QUESTIONS 20.1
1. When did the earth come into existence?
Ans: 4.5 to 5 billion years ago.
2. Why did life not exist on primitive earth?
Ans: Too hot and only certain gases present and reduce the atmosphere.
3. What are fossils?
Ans: Remains of organisms who lived in the past.
4. What is meant by the Cambrian explosion?
Ans: The time 600 millions years ago when sudden formation of different groups of invertebrates on the earth took place.
5. From the geological time scale, find out the time in million years ago(mya) when:
(i) Dinosaurs became extinct ______________.
Ans: 144-65 mya.
(ii) Human evolution began ______________.
Ans: 1.5-2 million years ago (mya).
(iii) flowering plants became dominant on earth ____________.
Ans: 57-34 mya.
INTEXT QUESTIONS 20.2
1. Who is Charles Darwin? Name his famous book on natural selection.
Ans: Founder of theory of evolution.
2. Mention his two major contributions.
Ans: The two major contributions are mentioned below:
(i) all organisms related through ancestry.
(ii) Mechanism of evolution is Natural Selection.
3. What is the function of Natural Selection?
Ans: Fittest individuals in a population survive and reproduce to leave the fit genes in the next generation.
4. What is meant by Neo Darwinism?
Ans: Darwin’s theory modified in the light of progress in genetics.
5. Name the evolutionary mechanism that causes organisms to evolve.
Ans: Natural Selection.
INTEXT QUESTIONS 20.3
1. When did human evolution begin?
Ans: 1.5 to 2 million years ago.
2. Who is ‘Lucy’?
Ans: Australopithecus.
3. Write the scientific name of Cro-magnon and Neanderthal man?
Ans: Homo sapiens.
4. With which group of animals do humans share their immediate ancestors.
Ans: Apes.
5. Name the earliest ancestors of modern day humans.
Ans: Australopithecus.
| TERMINAL EXERCISES |
1. What were the primitive conditions on earth? Tell your friend/cousin/ colleague. Then ask your friend to name the gas which was absent without which today no life can exist.
Ans: This earth was created about a million years ago. When this earth was created then the condition was not as today’s situation. Years after years the temperature changes to this and make an environment of living today’s ecosystem.
2. What are the main points of Oparin’s Theory of Origin of life? Make a five point quiz on it.
Ans: The life developed from microscopic spontaneously formed spherical lipid molecules held together by electrostatic forces, probably the earliest form of cells. These molecules most likely functioned as enzymes, essential for the biochemical metabolic reactions necessary for life’s evolution.
Five point quiz on it are:
(i) According to Oparin, what gas was likely missing from the early Earth’s atmosphere.
(a) Methane (CH4).
(b) Ammonia (NH3).
(c) Water Vapour (H2O).
(d) Free Oxygen.
Ans: (b) Ammonia (NH3).
(ii) Which of the following is NOT considered a building block of life according to Oparin’s theory?
(a) Amino Acids.
(b) Sugars.
(c) Salts.
(d) Proteins.
Ans: (d) Proteins.
(iii) What name did Oparin give to the microscopic spheres formed from organic molecules?
(a) Protocells.
(b) Coacervates.
(c) Nucleotides.
(d) Enzymes.
Ans: (b) Coacervates.
(iv) What process does Oparin’s theory propose was NOT crucial for the development of life?
(a) Formation of complex organic molecules.
(b) Creation of coacervates.
(c) Natural selection.
(d) Photosynthesis.
Ans: (c) Natural selection.
(v) Scientists like Stanley Miller performed experiments that supported which part of Oparin’s theory?
(a) Formation of coacervates.
(b) Development of the first cells.
(c) Origin of the reducing atmosphere.
(d) Natural selection.
Ans: (c) Origin of the reducing atmosphere.
3. Mention Darwin’s two major contributions to evolutionary ideas.
Ans: Two major contribution to evolutionary ideas are mentioned below:
(i) organisms through ancestry.
(ii) Theory of Natural Selection.
4. Write a note on NeoDarwinism.
Ans: Neo Darwinism is a modified theory of Darwinism explaining the origin of species on a genetic basis, hence the main driving force of Neo Darwinism is genetic variation. Consequently, the main difference lies in the variation type and type of natural selection.
5. List the five major events during the geological time period beginning from the origin of life. You may begin with the origin of animals.
Ans: The five major during events during geological time period beginning fro, of life are mentioned below:
(i) 4500 mya – Earth’s core and crust formed.
(ii) 4400 mya – The Earth’s first oceans formed.
(iii) 3850 mya – The first life appeared on Earth.
(iv) 1500 mya – Oxygen began to accumulate in the Earth’s atmosphere.
(v) 700 mya – The first animals evolved.
6. State major trends and stages of human evolution. Do you think humans are still evolving? Write five sentences to justify your response.
Ans: When human evolution began, forests had dwindled because of glaciation (ice age). Much of the land surface was, however, still covered by forests. The common ancestors of apes and humans had to come down from trees where they lived and walk on the ground using all four limbs. Recent molecular studies have shown that from common ancestors, evolution of apes (Chimpanzee, gorilla, gibbon and orangutan) and that of humans, diverged about 6 million years ago.
The trends of human evolution are towards
(i) Bipedal gait or walking on two legs. and
(ii) Acquiring a large brain.
Fossil history reveals that human evolution began approximately 1.5 to 2 million years ago. Australopithecus is deemed to be the first human-like ancestor. Fossils of an australopithecus named ‘Lucy’ has been found in African rock deposits. Thereafter, fossils of Homo erectus, which walked on two legs, were unearthed from many parts of the world.
The evolution is not stuck changing its pattern and this change we will see in future something about years after. In this way the new characteristics would be gained and go on developing.
7. Earlier groups of animals became extinct due to natural happenings. Today, how is it that wild animals have become endangered and are heading towards extinction.
Ans: Darwin in his theory tells us that which will capable of developing itself will go further otherwise will be extinct near future so some of animal doesn’t make themselves survived.
8. Write a ten sentence conversation between your father and yourself justifying the need for conservation of animals living in our forest.
Ans: Do yourself.
