KSEEB Solutions for Class 8 Science Chapter 22 Evolution of Life

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Karnataka State Syllabus Class 8 Science Chapter 22 Evolution of Life

KSEEB Class 8 Science Evolution of Life Textbook Exercise Questions and Answers

I. Four alternatives are given to each of the following incomplete statements/questions choose the right answer:

Question 1.
The phrase Hot dilute soup was used by
(a) Oparin
(b) Darwin
(c) Haldane
(d) Pasteur
Answer:
(c) Haldane

Question 2.
Which gas was absent in the atmosphere at the time of origin of life?
(a) ammonia
(b) hydrogen
(c) oxygen
(d) methane
Answer:
(c) oxygen

Question 3.
The first organisms on primitive earth were
(a) autotrophic
(b) heterotrophic and anaerobic
(c) parasitic
(d) prokaryotic and autotrophic
Answer:
(b) heterotrophic and anaerobic

Question 4.
The greatest weakness in Darwin’s theory was his failure to explain
(a) over production
(b) survival of the fittest
(c) struggle for existence
(d) variations
Answer:
(d) variations

II. Fill in the blanks with suitable words

Question 1.
1. Earth was a hot revolving ball of ……………….. about 4.8 billions of years age.
Answer:
gas

Question 2.
Lightest element hydrogen was found in the ………….. layer of the earliest earth.
Answer:
outermost

Question 3.
Variations caused by sudden genetic changes are called ……………..
Answer:
mutation

Question 4.
Darwin explained the survival of the fittest, but not their ………………..
Answer:
arrival

III. Match the following:

Answer:
1. d) theory of inheritance of acquired characters
2. c) theory of natural
3. b) mutation theory
4. e) theory of chemical evolution

IV. Answer the following

Question 1.
What is organic evolution?
Answer:
The slow and gradual process by which living organisms have undergone changes from the single called forms to the many-celled forms of life is known as organic evolution.

Question 2.
Explain Lamarck’s theory of use and disuse of organs with suitable examples.
Answer:
Lamarck’s theory is based on three main ideas,

1. new needs,
2. use and disuse of organs, and
3. Inheritance of acquired characters.

Use and disuse of organs For overuse: Giraffe’s ancestors were small as deer Giraffes started stretching their neck and forelimbs in order to reach the leaves of taller plants due to the severe competition from other herbivores and drought. This continued for several generations and as a result neck and forelimbs became longer.

For disuse: The ancestors of the snake had four well-developed limbs snakes were hunted by more advanced group of animals. In order to survive, they started crawling on the ground and spent most of their time hiding in crevices and holes. This resulted in the limbs becoming Degenerate and ultimately disappear.

Question 3.
What is the role of variations in evolution?
Answer:

1. Primitive life
2. Modification of life
3. Organelles modification

Question 4.
What is the mutation?
Answer:
Sudden changes to the genetic makeup of an organism when it is subjected to higher environmental temperature or high energy radiation is called a mutation.

Question 5.
Define Neo Darwinism
Answer:
Neo Darwinism is the modern theory on organic evolution, the synthesis of ideas from the theory of natural selection and mutation theory in the light of present knowledge on how mutation occurs.

Question 6.
Which organisms changed the earth’s atmosphere from reducing to oxidizing type?
Answer:

1. Algae
2. Animals

Question 7.
What were the limitations found in Darwinism and Lamarckism?
Answer:
Limitation in Darwinism

1. Darwin failed to recognize the source of variations in organisms
2. He had no idea of the mechanism of inheritance.
3. He explained the survival of fittest but not their arrival.

Limitation of lamarckism:

1. His theory cannot explain how body cells pass on the acquired characteristic to reproductive cells.
2. Experiments have shown that acquired characters are not inherited and inherited characters are not acquired.

KSEEB Class 8 Science Evolution of Life Additional Questions and Answers

I. Answer the following

Question 1.
What is meant by swan-necked flask experiments?
Answer:
Swan necked flask experiments were the experiments conducted by Louis Pasteur and proved that all forms of life arise only from pre-existing life.

Question 2.
Write the assumptions of the theory of chemical evolution.
Answer:
The theory of chemical evolution assumes that

1. Earth’s surface and atmosphere during the first billion years of its existence, were radically different from there of today’s conditions.
2. The primitive earth’s atmosphere did not have oxygen.
3. The first life arose from a series of chemical reactions.
4. Solar radiation, ultraviolet rays, lightning must have been the chief sources of energy for these chemical reactions.

Question 3.
How was earth in its initial days?
Answer:
In the initial days of earth’s formation, heavy elements such as iron and nickel were present in the centre of the earth and lighter ones such as aluminum, and silicon, in the middle layer. Elements like hydrogen, oxygen, carbon were found in the outermost layer. Due to the high temperature, these atoms could not combine but as the earth started cooling, these atoms started combining to form molecules.

Question 4.
Name the earliest molecules formed which became the basic molecules for the origin of life.
Answer:
The earliest molecules formed were those of H₂, N₂, NH₃, CH₄, CO₂ and water vapour which became the basic molecules for the origin of life.

Question 5.
Name the earliest organic molecules formed.
Answer:
Simple sugars, fatty acids, glycerol, amino acids and nitrogen bases were the earliest organic molecules formed which helped in the origin of life.

Question 6.
Explain Haldane’s view on the origin of life.
Answer:
As the earth cooled the simple organic compounds combined among themselves to form complex compounds. Due to the accumulation of these complex organic molecules, the seawater ultimately became a sort of a ‘hot dilute soup’. In this soup, molecules interacted and aggregated to form more complex molecules called coacervates.

Due to their affinity towards water molecules, an envelope of water molecules formed which increased the chemical reactions and started exhibiting the basic properties of life such as metabolism, growth, and reproduction.

In course of time coacervates became established into the first living systems known as protobionts, which functioned as the first enzymes and leading to the formation of first cells. The first forms of life obtained energy by the fermentation of organic compounds. They were thus heterotrophs and anaerobic organisms.

Question 7.
Explain the principle of Lamarckism
Answer:
1. New needs: Environment is highly unstable and subject to frequent changes which created new needs in the organism.

2. Use and disuse: The needs force the organism to put additional efforts that a particular part of the body into more frequent use or may not use it. This idea is use and disuse. Any part that is more used likely to grow more and in the same way the part that is not used becomes less prominent and may disappear.

3. Inheritance of acquired characters: These characters acquired by an organism get transmitted to future generations.

Question 8.
Mention the drawbacks of Lamarck’s ideas.
Answer:

1. His theory cannot explain how body cells pass on the acquired characteristic to reproductive cells.
2. Experiments have shown that acquired characters are not inherited and inherited characters are not acquired

Question 9.
Write the drawbacks of Darwin’s theory.
Answer:
Darwin failed to recognize the source of variations in organisms. He had no idea of the mechanism of inheritance. He explained the survival of the fittest, but not their arrival.

II. Fill in the blanks:

Question 1.
Haldane suggested that due to the accumulation of complex organic molecules, the seawater became a sort of a ………………………
Answer:
hot dilute soup

Question 2.
The large-sized particles formed due to the force acting between the aggregated large molecules have been called as ………………
Answer:
coacervates

Question 3.
The protobionts which developed the ability to lead up the chemical reaction where called as …………….
Answer:
enzymes

Question 4.
The life forms present in 2.5 billion years age were called as …………….
Answer:
protobionts

Question 5.
The life span of elephants is about ………………..
Answer:
90years

Question 6.
The lower t reproducing animal is ………………..
Answer:
elephant

Question 7.
The sudden change in the genetic material is known as …………….
Answer:
mutation

Question 8.
The book published by Lamarck is ……………..
Answer:
Philosophic Zoologique

Question 9.
The Lamarckian theory was referred by ………………..
Answer:
August Weisman

Question 10.
The book published by Darwin is ………………..
Answer:
Origin of Species.

III. Choose the best alternative.

Question 1.
The long neck formation of Giraffe was explained by
(a) Lamarck
(b) Darwin
(c) Devries
(d) Oparin
Answer:
(a) Lamarck

Question 2.
The theory of chemical evolution was suggested by
(a) Lamarck
(b) Darwin
(c) de Vries
(d) Oparin
Answer:
(d) Oparin

Question 3.
The theory of mutation was proposed by
(a) Lamarck
(b) Darwin
(c) de Vries
(d) Oparih
Answer:
(c) de Vries

Question 4.
The famous swan-necked flask experiment was condutcted by
(a) Lamarck
(b) Louis Pasteur
(c) Oparin
(d) Darwin
Answer:
(b) Louis Pasteur

Question 5.
The present theory of evolution is
(a) Lamarckism
(b) Darwinism
(c) Theory of chemical evolution
(d) Neo Darwinism
Answer:
(d) Neo Darwinism