KSEEB Solutions for Class 8 Science Chapter 22 Evolution of Life

Karnataka Board Class 8 Science Chapter 22 Evolution of Life

KSEEB Class 8 Science Chapter 22 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statement / question choose the right answer.

Question 1.
The term not 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.
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)
2. (c )
3. (b)
4. (e)

IV. Answer the followings:

Question 1.
What is organic evolution
Answer:
The slow gradual process by which living organism have undergone changes from the single celled 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 example.
Answer:
A Lamarck’s theory is based on three main ides namely new needs, use and disuse of organs and inheritance of acquired characters. The appearance of new needs forces the organism to put in additional efforts to fulfill. It may put a part of a body into more and more frequent use.

Similarly, it may also be necessary for an organism to put a part of its body into less use or may not use at all. This idea is known as use and disuse of organs. Any part of the body that is more and more used is likeiy to grow larger and become better and stronger.

In the same way any part of body which is less frequently used has the tendency to become less prominent and may even ultimately disappear. Thus by a differential over use and disuse of various body parts, an organism would change to some extent and acquire new characters.

For example: for over use: 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. Example for disuse: The ancestors of 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 -heir 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:
Darwin found that generally, the young ones of an organism show differences compared to the parent. He described the differences as variations which are the rule of nature which helps an organism to adjust better to the environment.

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.
What is 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:
The appearance of autographs in the form of blue-green algae changed the situation on earth. These organisms released free molecular oxygen into the atmosphere, gradually transforming it into an oxidizing type.

Question 7.
What were the limitations found in Darwinism and Lamarck ism?
Answer:

1. Limitation in Darwinism
   • Darwin failed to recognize the source of variations in organisms
   • He had no idea of the mechanism of inheritance.
   • He explained the survival of fittest but not their arrival.
2. Limitation of Lamarck ism
   • His theory cannot explain how body cells pass on the acquired characteristic to reproductive cells.
   • Experiments have shown that acquired characters are not inherited and inherited characters are not acquired.

KSEEB Class 8 Science Chapter 22 Additional Questions & Answers

I. Answer the following :

Question 1.
Who is the scientist conducted a swan-necked flask experiment?
Answer:
The famous swan-necked flask experiment was conducted by Louis Pasteur.

Question 2.
Explain swan-necked flask experiment.
Answer:
The famous swan-necked flask experiment was conducted by Louis Pasteur. and he proved beyond doubt that all forms of life arise only from preexisting life.

Question 3.
Who proposed theory of chemical evolution?
Answer:
Theory of chemical evolution was proposed by oparin and Handane independently.

Question 4.
Write the assumptions of theory of chemical evolution.
Answer:
Assumptions of theory of chemical evolution are:

1. The Earth’s surface and atmosphere during the first billion years of its existence were radically different from those of days 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, and lightning must have been the chief sources of energy for these chemical reactions.

Question 5.
Explain the initial days of Earth’s.
Answer:
In the initial days of earth’s formation, heavy elements such as iron and nickel were present in the center of the earth. Comparatively lighter ones like aluminum and silicon formed the middle layer, elements like hydrogen, oxygen and carbon were found in the outermost layer. Due to the high temperature, the atoms of these elements could not combine to the molecule as the earth started cooling gradually the atoms started combining to form molecules.

Question 6.
Mention the earliest molecules formed which became the basic molecules for the origin of life.
Answer:
The earliest molecules formed were those of H_2, N_2, NH_3, CH_4, CO₂ and water vapor which became the basic molecules for the origin of life.

Question 7.
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 8.
Explain Haldane’s view on origin of life.
Answer:
As the earth cooled. The simple organic compound combined among them selves to form complex organic compounds, due to the accumulation of these complex organic molecules, the sea water ultimately became a sort of a ‘hot dilute soup’. In this soup, molecules interacted and aggregated to form more complex molecules called coaCervantes.

Due to their affinity towards water molecules an envelope of water molecules formed which increased the chemical reactions and stalled exhibiting the basic properties of life such as metabolism growth and reproduction. In course of time coacervates became established in to the first living system known as prolobionts.

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 9.
What is organic evolution?
Answer:
The slow gradual process by which living organisms have undergone changes from the single-celled forms to the many-celled forms of life is known as organic evolution.

Question 10.
Mention the principles of Lamarck ism theory.
Answer:
The Lamarck ism theory is based on three principles they are:

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

Question 11.
Mention the drawbacks of Lamarck’s ideas.
Answer:
Lamarck’s ideas had some-drawbacks.

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 12.
Who proposed a theory of Natural Selection.
Answer:
Charles Darwin proposed a theory of Natural selection in 1859. It is more popularly known as ‘Darwinism’.

Question 13.
Mention the principles of Darwinism theory.
Answer:
Darwinism theory is based on the following principles.

1. Overproduction
2. Struggle for existence
3. Variation
4. Natural selection
5. Survival of the fittest.

Question 14.
Explain Darwin’s theory of overproduction.
Answer:
Overproduction: All organisms have a natural capacity to produce a large number of young ones. This capacity is known as overproduction.

Question 15.
Explain Darwin’s theory of the struggle for existence.
Answer:
As a result of high rate of reproduction, there must be competition between individuals. It is for sharing food water, living space and other resources. This competition was described by Darwin as a struggle for existence.

Question 16.
Explain Darwin’s principles of variation.
Answer:
Generally, the young ones show differences compared to the parents. This is variation and they help the organisms to adjust better to the environment.

Question 17.
Explain Darwin’s principles of Natural selection.
Answer:
According to Darwin nature selects only those organisms that have favorable variations.

Question 18.
Explain the survival of the fittest.
Answer:
The naturally selected organisms which have developed advantageous variations have a better chance of survival less adopted or not adopted get eliminated. This idea is known as survival of the fittest.

Question 19.
Mention 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 fittest but not their arrival.

KSEEB Solutions for Class 8 Science