Origin and Evolution of life Questions and Answers-2.

Origin and Evolution of life Questions and Answers-2. 

Q.1. What were the events of biological evolution that followed chemical evolution?
Ans:- 1) The evolutionary rocess after the origion of first cell was called biological evotution.
2) The first cells were marine and had hetero-tropic mode of nutirtion taking good from their surroundings.
3) Due to growth and multiplication of these cells, there was depletion in the food and increase in CO2, due to fermentation.
4) During this phase, chromatophores were developed by mutation. They could trap the light energhy and convert it into chemical energy.
5) The heterotrophs started autotrophic mode by starting photosynthesis in them. Oxygen was thus released as a byproduct of photosynthesis. In this way, the primitive reducing atmosphere gradually changed into oxidizing atmosphere.

 
Q.2. Describe the coacervate theory of Oparin.
Ans :- 1)   Coacervate is the term given by oparin to substances present on the primitive earth.
2)   From coacervates the first cell-like forms called “protobionts” or “eubionts” were probably formed.
3)   The transformation of nonliving substances into living forms took place from coacervates.
4)   Oparin also performed experiment to show that the formation of protein molecule was a very crucial event in the course of chemical evolution.
 

Q.3. Describe the microsphere theory of Sydney Fox.
Ans:- 1) Microsphere is the term given to spherical colloidal droplets which were formed during experiments that Dr. Sydney Fox performed.
2) His experiments were done by simulation prebiotic environmental conditions in the laboratory.
3) When amino acids were heated they polymerized into protein like droplets called proteinoids.
 
Q.4. Describe the Urey and Miller’s experiment.
Ans :- 1) Urey and Miller performed an experiment to prove Oparin’s theory of chemical evolution.
2) They selected a spark discharge apparatus that consisted of closed system of glass having tungsten electrodes, flask for water boiling, a side tube connected to a vacuum pump, a cooling jacket and U-shaped trap.
3) The entire apparatus was first evacuated and made sterile and pre-biotic atmosphere was created in it.
4) The flask was filled with some water and mixture of methane, ammonia and hydrogen in the ration of 1:2:2 were slowly passed through the stopcock, without allowing air.
5) Heat was supplied to the flask at very low temperature causing water to boil. The flask simulated the ocean present on primitive earth.

6) Water vapours along with other gases were circulated continuously through the high electric sparks of 75,000 volts. Continuous electric sparks were given to the mixture for seeral days causing the gases to interact. This too simulated lightning.
7) Mixture of gases passed through a condenser and was condensed to liquid.
8) The liquefied mixtyure was collected in the trap, present at the bottom of the apparatus. It was foudn that variety of simple organic compounds (amino acids and sugars) were formed in the aparatus.
 
Q.5. What is the significance of Urey and Miller’s experiment?
OR
What was the major inference of Urey and Miller’s experiment ?
Ans :- 1) Urey and Miller demonstrated the formation of amino acids, sugars and other simple organic compounds by simulation the conditions that might have prevailed on the primitive earth in the laboratory.
2) They provided vital proof that the essential building blocks (nucleotides, amino acids, etc) for the first living organisms could have been formed on primordial earth.
3) It also showed that the synthesis of the first proteins was probably due to non-enzymatic reactions.
 
Q.6. Define Evolution ?
Ans :- Organic evolution can be defined as slow, gradual, continuous and irreversible changes through which the present day complex forms have descended from their simple pre-existing forms of the past.
 
Q.7. Describe Darwin’s theory of Natural selection.
Ans:- Darwin’s theory of natural selection :- 

Darwin’s theory of natural selection is based on the following principles :-
1.   Overproduction or enormous fertility or prodigality of production : Every living organism has a great potentiality of reproduction. Only few can survive up to maturity whereas many perish. Then too, there is overproduction.
2.   Struggle for existence : Organisms multiply in geometric ration but the space and food remain constant leading to competition for survival. This competition is called struggle for existence. The struggle may be intraspecific, interspecific or environmental.
3.   Variations and heredity :- Variations are the differences between individuals of the same species. Types of variations are unfavorable, neutral or favorable. The favorable variations are preserved and passed on to their offspring’s.
4.   Survival of the fittest or Natural selection :- The organisms having useful and favorable variations are the fittest for survival. While the organisms with unfavorable variations are not selected by nature while those with favorable variations are selected by nature. This is called survival of fittest or theory of natural selection.
5.   Origin of new species :- A new species originates by the gradual accumulation of favorable variations for a number of generations. The favorable characters are transmitted to the next generation in case of fittest organisms. Later a new species is formed.
 

Q.8. State the objections raised against the Darwin's theory of Natural selection.
Ans. Objections to Darwin's theory of Natural selection: 

The objections raised against Darwin's theory of Natural selection are as follows:
(1) Darwin could not explain the arrival of the Fittest'. He simply insisted on survival of the Fittest.
(2) He did not consider the hereditary principles.
(3) He did not differentiate between somatic and germinal variations.
(4) This theory has no satisfactory explanation for the cause, origin and inheritance of variations.
(5) Darwin's theory of Natural selection does not give any idea about the inheritance of useless variations like the vestigial organs.

 
Q.9. Write a note on “struggle for existence”. OR Explain the concept of 'struggle for existence'.
Ans. Struggle for existence: Struggle for Existence is one of the principles in the theory of Natural selection as proposed by Darwin. Individuals multiply in geometric ratio but the space and food remains constant. This leads to struggle for existence. The struggle may be Intraspecific, inter-specific or environmental.
(1) Intraspecific struggle: Intraspecific struggle is the competition among the individuals of the same species. This is a severe struggle because the need and approach of all competing organisms is similar, e.g., struggle between two Herbivore animals for getting grass.
(2) Interspecific struggle: Interspecific struggle is the competition between the organisms of different species living together for food, shelter and breeding places. E.g. struggle between a parasite and host or a predator and prey.
(3) Environmental struggle: Environmental struggle is struggle shown by all living forms against adverse environmental conditions or against natural calamities like extreme heat or cold, drought, storms, earthquakes, volcanic eruptions, etc.
 
Q.10. Describe or Explain the concept of “Survival of the fittest”.
Ans. Survival of the fittest or Natural selection:
(1) The organisms having favorable variations succeed in the struggle for existence.
(2) These organisms are the fittest for survival.
(3) Since the organisms with unfavorable variations are unfit to survive, they perish.
(4) This shows that there is survival of the fittest.
(5) Since the nature selects the organisms with favorable variations which are fittest to survive, hence, the theory is known as the theory of Natural selection.
(6) The organisms with unfavourable variations are eliminated from the population. 
 
Q.11. Explain the theory proposed by Hugo de Vries.
Ans. (1) Hugo de Vries proposed mutation theory to
explain the process of organic evolution.
(2) The term mutation means sudden large change taking place in the genetic material of the organisms that are heritable.
(3) He studied evening primrose plants (Oenothera lamarkiana) for seven generations.
(4) Certain striking differences in the forms were observed in these plants, which appeared suddenly amongst a population of normal evening primrose plants.
(5) These new traits also bred true.
(6) Hugo de Vries called this phenomenon as mutation while the changed forms were called mutants.