NEET Exam  >  NEET Notes  >  Biology Class 12  >  Biological Evolution: Miller Urey & Louis Pasteur Experiment

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET PDF Download

Experimental evidence for formation of simple organic compounds – 

By Stanley Miller who was a student of Harold Urey.  

In this experiment Miller took the mixture of methane, ammonia and hydrogen (ratio 2 : 1 : 2) in a large flask and passed steam over it by boiling  water and connecting it with a glass tube.

Electric spark discharged in the mixture by using two tungsten electrodes as source of energy. 

After 18 days this fluid was collected and analysed. This dark red fluid was found to contain.

–    Simple amino acids – glycine, alanine, aspartic acid.

–    Simple organic acids – formic, acetic, oxalic, lactic, succinic acids.

–    Pentose, hexose, aldehyde, ketone etc. 

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET


Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

BIOLOGICAL EVOLUTION : 

(i) Origin of  Protobionts and Nucleoprotein (Coacervates) 

Macro molecules which were synthesized abiotically in primitive ocean later came together and formed large colloidal drop like structures named as Protobionts (Later called coacervates by oparin, Fox and called them Microsphere and Deamer called them vesicles).

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

  • Each protobiont was cluster of macro molecule.
  • They contain proteins, nucleic acids, lipids, polysaccharides etc.
  • They grew by absorbing molecules from their environment.
  • They could divide by budding like bacteria, many chemical reactions including the decomposition of glucose took place inside the protobionts.
  • The sun provide energy for chemical reaction.
  • According to oparin coacervates were the first sole living molecules which gave rise to cell. 

Different type of Protobionts obtained by scientists

Oparin (1924) took a solution of carbohydrate and large protein. The solution was shaken. It caused separation of coacervates.

In coacervates higher concentration of protein, carbohydrate were present with small amount of water.

Oparin's coacervates could grow and exhibit simple form of metabolism. However a lipid membrane and reproduction was absent.

Fox (1957) obtain microspheres with a primitive membrane. He heated dry mixture of Amino acids at 130° -180° C. It formed PROTEIDS PROTEXOIDS (Polymer of ammo acid).

When these proteids poured in Cool water along with lipids, microsphere get separated, (size 1-2 p m) 
Dearner (1993) Microsphere and coacervates could fused to form protobionts having various type of chemicals like proteins, Nucleic acids, Carbohydrates etc. enclosed inside a lipid membrane. Dearner called them vesicles.

(ii) Origin of protocells [Eobiont] : 

The first living form named protocell originated in the primitive oceans.

The protocell were clusters of nucleo-proteins which formed by composition of nucleic acids and enzymetic proteins.

Nucleo proteins had the property of self duplication.

Nucleo proteins were first sign of life. 

The protocell represented the beginning of life.

From protocells or eobionts few core of nucleoproteins gets separated free in oceans and became inactive but when they enter in another bionts they became active so virus like structures were formed.

Origin of virus like structure is an example retrogressive evolution (complex to simple).

Important

1. Khorana (1970)artificially synthesized 77 nucleotide RNA molecule out side a living cell which suggests that probably RNA was the primordial genetic material rather than DNA. 

Zaug, Thomas cech and Altman described that some RNA molecules have enzymatic activity hence probably the RNA enzymes called ribozymes were able to replicate the primordial RNA. 

The discovery of RNA molecule working as enzyme has also changed our thinking about origin  of  life. 

It is now believed that about 4 billion years ago earth was an 'RNA world' in which RNA molecule carried out all the process of life without the help of either protein or DNA, 

By this discovery evolution is named as RNA world.

2. It is estimated that life originated about 3.0 billion years ago as protocell (eobionts) in precrambian era which was anaerobic heterotrophic. 

(iii) Origin of Prokaryotes – 

As a result of mutation the protocells became more complex and efficient and used the materials available in the surrounding medium and condensed themselves into prokaryotic cells.

Thus the first living being were prokaryotic, like bacteria they were single celled and consisted of naked DNA. Nutritionally they were chemo heterotrophs (saprotrophs), respiration was anaerobic.

(iv) Origin of Autotrophism – 

It includes the origin of chemosynthesis and photosynthesis.

(a) Origin of chemosynthesis : 

Due to continue withdrawal of organic molecules by chemo heterotrophs organic material decreased in oceans.

Before the organic material disappeared in sea, new modes of Nutrition developed, one of them was chemosynthesis.

The organism which perform chemosynthesis are called as chemoautotrophs. They were anaerobic and synthesise organic molecules from inorganic material. The energy was obtained by oxidizing inorganic materials present in the sea.

Such mode of nutrition is found in Bacteria e.g. sulphur bacteria, nitrifying bacteria. 

(b) Origin of Photosynthesis : 

After some time bacterio-chlrophyll developed in some autotrophic bacteria like organism.

They could absorb solar energy and convert it into chemical form these organism called photoautotrophs.
They utilize solar energy in synthesizing organic compounds. The process is called photosynthesis.

They were anaerobic and utilized hydrogen from sources other than water like H2S.

Therefore, no oxygen was evolved and atmosphere remained reducing .

This stage of photosynthetic autotrophism is represented by planktonic sulphur bacteria of today.

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

Oxygen revolution – 

Liberation of free O2 by blue green algae like prokaryotes due to photosynthesis was a revolutionary change in the history of earth. It is called oxygen revolution. 

It includes important changes like –

(1)  Atmosphere of earth changed from reducing to oxidising, hence possibilities of further chemical evolution and a biogenesis got over, because chemical evolution always take place in reducing environment.

(2)  Free O2 oxidized CH4 and NH3 to form gases like CO2 , N2 and H2O.

(3) Accumulation of free O2 formed a layer of O3 (ozone) above the atmosphere of earth, which started absorbing most of the U.V. rays of sunlight.                   

Origin of Eukaryotic cell – 

About 2.7 billion years ago conditions become suitable for aerobic respiration with the release of free O2 . Aerobic respiration yields about 20 times more energy then anaerobic respiration hence the prokaryotes adapted themselves for aerobic mode of respiration.

Nucleus, mitochondria and other cell organelles developed in the cell and free living eukaryotic cell like organism originated about 2.0 billion years ago in the primitive ocean.

Organic Evolution – 

1. Though life originated by chemical evolution on primitive earth, was later replaced by organic evolution.

2. Organic evolution states ''Descent with modification''. i.e. the present day complex organism have evolved from earlier simpler organism by small but gradual changes which have occurred over millions of years.

3. Though living organisms show diversity in size, structure, function, behaviour etc. they also show basically similar metabolic processes indicating common ancestory. 

Points to remember :

1.  Evolution up to formation of coacervates termed as chemical evolution, in which complex organic compound were formed which were essential for formation of cellular structure.

2.  Evolution from coacervates to simple cell structure known as biological evolution.

3.  From simple cell to recent…..evolution is called organic evolution, in which organism developed structures and modified them by which they became more adaptive in their changing environment.  

4.  First protein which is formed during evolution in primitive oceans were not structural.

5. First nucleic acid which was formed in primitive oceans from combination of nucleotides, did not have power of replication. They obtained power of replication later by mutation.

6.   Evolution term introduced by - Herbert Spencer. 

       Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

 Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

7.   What is evolution ?

The word evolution  means to unfold or unroll or to reveal hidden potentialities. Evolution simple means an orderly change from one condition to another.

8.   Evolution is a slow but continuous process which never stop-Buffon.

9.   Dollo's low – it states that evolution is irreversible.

10. According to Theodosius Dobzhansky (1973), nothing in biology makes sense except in the light of  evolution.

11. Scala nature or ladder of nature : – 

Aristotle represented the evolution of complex organism from simple organism in the form of a ladder which is called Scala Nature or Ladder of nature.

He kept simple organism at the bottom of ladder and complex organism at the top of this ladder.

George cuvier studied the evolutionary history of organism by studying fossils and rejected Scala nature.

12. The history of life actually comprises two events :

(i)   The origin of life

(ii)  Evolution of life [the mechanism involved in the changes of living organisms through time]  

13. Two great themes of evolutionary biology :

(i) The diversity of life, including both the differences and similarities.

(ii) The characteristics of   organism, both adaptive and non-adaptive.

14. For origin of life, at least three conditions needed to have been fulfilled.

(i)   There must have been a supply of replicators i.e. self producing molecules.

(ii)  Copying of these replicators must have been subject to error via mutation.

(iii) The system of replicators must have required a perpetual supply of free energy and partial isolation from
the general environment.

15. Cosmology–Study of universe.

16. Biological evolution is also known as biogeny.

17. Unit of evolution is population.

18. Oparin's theory also known as primary abiogenesis.

19. Evolutionary biology-Study of history of life forms on earth.     

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

The document Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET is a part of the NEET Course Biology Class 12.
All you need of NEET at this link: NEET
158 videos|393 docs|239 tests

FAQs on Biological Evolution: Miller Urey & Louis Pasteur Experiment - Biology Class 12 - NEET

1. What is the Miller-Urey experiment and how does it relate to biological evolution?
Ans. The Miller-Urey experiment was conducted in 1952 to simulate the conditions thought to be present on early Earth. It aimed to test the hypothesis that the basic building blocks of life, such as amino acids, could have formed spontaneously from simple inorganic compounds in the atmosphere. The experiment involved creating a closed system with a mixture of gases, simulating the early Earth's atmosphere, and then subjecting it to electrical sparks to mimic lightning. The result was the formation of various organic compounds, including amino acids, which are the building blocks of proteins. This experiment provides support for the hypothesis that the chemical building blocks of life could have arisen through natural processes, contributing to our understanding of the origins of life and biological evolution.
2. Who was Louis Pasteur and what was his contribution to the understanding of biological evolution?
Ans. Louis Pasteur was a French chemist and microbiologist who made significant contributions to various fields, including biology and medicine. His experiments on fermentation and pasteurization demonstrated that living organisms are responsible for the biochemical changes observed in organic matter. Pasteur's work directly challenged the concept of spontaneous generation, which posited that life could arise spontaneously from non-living matter. His experiments supported the idea of biogenesis, the theory that life can only arise from pre-existing life. This understanding of the origin of life aligns with the principles of biological evolution, as it proposes that all organisms share a common ancestry and have evolved from simpler forms.
3. How did the Miller-Urey experiment provide evidence for the chemical origins of life?
Ans. The Miller-Urey experiment provided evidence for the chemical origins of life by demonstrating that simple organic compounds, such as amino acids, can be formed under conditions that were thought to be present on early Earth. The experiment simulated the early Earth's atmosphere, consisting of gases like methane, ammonia, water vapor, and hydrogen, and subjected it to electrical sparks to simulate lightning. After a week, the scientists observed the formation of various organic compounds, including amino acids, which are essential for the formation of proteins, the building blocks of life. This experiment supported the hypothesis that the basic building blocks of life could have arisen through natural processes, providing insights into the chemical origins of life and supporting the theory of biological evolution.
4. How did Louis Pasteur's experiments on fermentation and pasteurization contribute to our understanding of the role of microorganisms in biological evolution?
Ans. Louis Pasteur's experiments on fermentation and pasteurization were instrumental in furthering our understanding of the role of microorganisms in biological evolution. His experiments demonstrated that living organisms, specifically microorganisms, are responsible for the fermentation process, where sugars are converted into alcohol and carbon dioxide. Pasteur's work also showed that heating liquids to specific temperatures could kill microorganisms and prevent spoilage, a process known as pasteurization. These findings highlighted the importance of microorganisms in various biological processes and emphasized their role in shaping the evolution of life on Earth. Microorganisms have played a significant role in the diversification and adaptation of species, and Pasteur's experiments provided a foundation for understanding their influence on biological evolution.
5. How do the Miller-Urey experiment and Louis Pasteur's work support the theory of biological evolution?
Ans. Both the Miller-Urey experiment and Louis Pasteur's work support the theory of biological evolution by providing evidence for the natural processes that could have led to the origin and development of life on Earth. The Miller-Urey experiment demonstrated that under conditions thought to be present on early Earth, simple organic compounds, such as amino acids, could be formed. These compounds are crucial for the formation of proteins, which are essential for the structure and function of living organisms. This experiment suggests that the chemical building blocks of life could have arisen through natural processes, supporting the idea that all organisms share a common ancestry and have evolved from simpler forms. Similarly, Pasteur's experiments on fermentation and pasteurization revealed the role of microorganisms in various biological processes. His findings demonstrated that living organisms are responsible for the biochemical changes observed in organic matter. This understanding of the importance of microorganisms in shaping biological processes supports the theory of biological evolution, which posits that species have evolved and diversified over time through natural selection and adaptation. Therefore, both the Miller-Urey experiment and Pasteur's work contribute to the body of evidence supporting the theory of biological evolution.
158 videos|393 docs|239 tests
Download as PDF
Explore Courses for NEET exam

How to Prepare for NEET

Read our guide to prepare for NEET which is created by Toppers & the best Teachers
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Download the FREE EduRev App
Track your progress, build streaks, highlight & save important lessons and more!
Related Searches

Semester Notes

,

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

,

Free

,

Important questions

,

video lectures

,

Previous Year Questions with Solutions

,

study material

,

MCQs

,

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

,

Summary

,

mock tests for examination

,

Objective type Questions

,

Biological Evolution: Miller Urey & Louis Pasteur Experiment | Biology Class 12 - NEET

,

Viva Questions

,

practice quizzes

,

past year papers

,

Extra Questions

,

Sample Paper

,

ppt

,

shortcuts and tricks

,

Exam

,

pdf

;