Origin and Evolution of life Questions and Answers-1.

 

Questions & Answers

Introduction

Q.1) How did solar system come into existence ?

Ans :- 1) There was a single titanic explosion called the "Big Bang" about 15 billion years ago.

2) With this big bang, all the matter and tremendous energy came into existence. This resulted int he formation of the universe.

3) The fragments of the fire ball expanded and cooled gradually.

4) This gave rise to many more celestial bodies.

5) Further, over a span of many millions of years solar system was formed consisting of the sun and planets.

 

Origin of life

Q.2) Enlist the theories of origin of life, who put forth these theories?

Ans :- There are different theories of origin of life proposed by different scientists. They are as follows :

1) Theory of special creation : Father Sudrez

2) Cosmozoic theory : Richter

3) Theory of spontaneous generation : Put forth by Greek philosopher in 600 B.C. and later supported by Aristote.

4) Theory of biogenesis : Francisco Redi, Spallanzani and Louis Pasteur.

 

Q.3) Write short notes on Theory of special creation.

Ans : 1) Thoery of special creation is the oldest of all theories.

2) Father Sudrez proposed the theory of special creation.

3) According to this theory, all the living beings on the earth were specially created by God or by some supernatural power.

4) It is supported by major religions and civilizations.

5) For a long time people believed in the theory of special creation.

 

Q.4) Write short notes on Cosmozoic theory.

Ans :- 1) Cosmozoic theory is also called Panspermia theory. It was proposed by Richer. According to this theory, life on the earth came from a distant planet in the form of spores or microorganisms.

2) These spores were named cosmozoa or panspermia.

3) they were believed to be preserved insinde metorites.

4) These meteorites were in the form of massof matter from outer space.

5) They struck the barren earth to release the cosmozoa which in turn developed into various creatures.

6) Thomson, Helmholtz and Von Tieghem supported the Cosmozoic theory. However, this theory could not explain the origin of life on other distant planets.

 

Q.5) Write short notes on Theory of spontaneous generation or theory of abiogenesis.

Ans :- 1) The theory of spontaneous generation or theory of abiogenesis is also referred to as theory of autobiogenesis.

2) Abiogenesis is the idea initially put forth by Greek philosophers. It was also supported by Aristotle.

3) According to this theory, life originated from nonliving material spontaneously, without any interruption.

4) Louis Pasteur later disproved the theory of spontaneous generation by performing many experiments.

 

Q.6) Write short notes on Theory of biogenesis.

Ans :- 1) According to the theory of biogenesis, living organisms are always produced from pre-existing living forms by reproduction and not from nonliving or lifeless matter.

2) This theory was proposed by Francisco Redi, Spallanzani and Louis Pasteur.

3) They conducted classical experiments to disprove the theory of abiogenesis and then put forth the theory of biogenesis.

4) However, the theory of biogenesis could not explain the origion of "first life" on the earth. The theory of biogenesis could satisfactorily explain the continuity of life.

 

Q.7) What is explained by modern self-assembly theories?

Ans :- 1) Modern self-assembly theory as given by Fox, Dose and Lehinger, explains that origin of life on the primitive earth or protobiogenesis occurred due to inherent property of chemical molecules to produce self-organization or self-assembly.

2) Their suggestions were based on a model that explains the primordial events of conversion of micro-molecules into macromolecules. Such conversions formed organized cell-like micro-system.

3) To explain these concepts some scientists like Schmitt, Reed, etc. performed some experiments.

4) Schmitt synthesized collagen form simple micromolecules.

5) Reed demonstrated an intermacromolecular assembly by assembling two protein molecules which resulted into enzymatically active complexes.

6) During the origin of life, information or proto-information passed form amino acids in the geochemical matrix to protein in the first organism. This was the important conclusion derived from the model of self-assembly.

 

Q.8) Describe any three steps of Oparin-Haldane theory of chemical origin of life

OR

Enlist the steps of chemical origin of life as described by Oparin and Haldane.

Ans :- Oparin and Haldane proposed the theory of chemical origin of life :

1. Origin of earth and its primitive atmosphere :-

The earth of originated about 4.6 billion years ago. The initial super hot earth cooled gradually leading to the condensation of gases. Due to physical processes the heavy elements, sank to the centre and the lightest elements formed the atmosphere of the earth. The atmosphere of primitive earth around 3600 million years ago was reducing type without free oxygen.

2. Formation of ammonia, water and methane :-

The primitive earth had a large amount of hydrogen, nitrogen, carbon and oxygen. These molecules interacted with each other under high temperature and formed H2O as steam and NH3, CH4 in gaseous form. Later, steam was condensed and formed rain, causing cooling of earth. Ammonia and methane dissolved in rain and accumulated in the seas formed by falling rainwater.

3. Synthesis of simple organic compounds or micromolecules :-

In the next step, highly reactive free radicals -Ch and CH2 condensed to form hydrocarbons. Energy sources, for the reactions such as condensation, polymerization oxidation, reduction, etc. were ultraviolet rays, radiations, lightning and volcanic activities. Hydrocarbons, ammonia and water which were formed combined into monosaccharides, amino acids, purines, pyrimidines, fatty acids, glycerol, etc. Haldane gave the term hot dilute soup or primitive broth to these organic substances present in sea water on primitive earth.

4. Formation of complex organic compounds or macromolecules :-

The macromolecules were formed in the hot dilute, sterile and oxygen-free soup. New complex macromolecules such as polysaccharides, fats, proteins, nucleosides and nucleotides, etc. were formed due to polymerization reaction. These were called protoproteins which showed enzymatic reaction. The formation of protein molecule is a landmark in the origin of life.

5) Formation of nucleic acid :-

The next step was formation of nucleic acid by aggregation of phosphoric acid, sugar, purines and pyrimidines that formed nucleotides.

6) Formation of protobiont or pre-cells :-

The first form of life called protobionts or pre-cells were formed by nucleic acid along with inorganic and organic molecules which had self replication ability. The proteins were in form of coacervate4s or protenoids or micropheres.

7) Formation of first cell :-

The nucleic acid in pre-cells multiplied and gradually started directing protein synthesis. The transformation of pre-cell into a cell was an important step in origin of life.