ORIGIN OF LIFE.pptx

Life, living matter are those that shows certain attributes that include responsiveness, growth, metabolism, energy transformation and reproduction.
In biology origin of life or abiogenesis is the natural process by which life has arisen from non-living matter, such as simple organic compounds.
It means the emergence of heritable and evolvable self-reproduction.
It is a complex subject and oftentimes controversial.
Several attempts have been made from time to time to explain the origin of life on earth.
There are several theories which offer their own explanation on the possible mechanism of origin of life.

1. ASSAM UNIVERSITY, SILCHAR DEPARTMENT OF LIFE SCIENCE PRESENTED BY : KUKI MONJORI BORUAH ROLL NO- 11 DEPT. OF EARTH SCIENCE ORIGIN OF LIFE

2. CONTENT INTRODUCTION EVIDENCE FOR ORIGIN OF LIFE THEORIES OF ORIGIN OF LIFE PRE-MODERN THEORIES MODERN THEORIES RECENT DEVELOPMENTS CONCLUSION REFERENCES

3. INTRODUCTION Life, living matter are those that shows certain attributes that include responsiveness, growth, metabolism, energy transformation and reproduction. In biology origin of life or abiogenesis is the natural process by which life has arisen from non-living matter, such as simple organic compounds. It means the emergence of heritable and evolvable self-reproduction. It is a complex subject and oftentimes controversial.

4. EVIDENCE FOR THE ORIGIN OF LIFE There are at present four primary sources of information The record of the early solar system, as preserved in comets or carbonaceous chondrites. The record of terrestrial rocks- geology. The record of ancient microorganisms and their physiological activities- palaeobiology. The phylogenic history recovered in the nucleotide and amino acid sequences found in molecular cells- molecular phylogeny.

5. THEORIES OF ORIGIN OF LIFE Several attempts have been made from time to time to explain the origin of life on earth. There are several theories which offer their own explanation on the possible mechanism of origin of life. They can be categorized into two groups- Pre-Modern theories Modern theories

6. ORIGIN OF LIFE SPECIAL CREATION EXTRA-TERRESTRIAL ORIGIN SPONTANEOUS ORIGIN BIOCHEMICAL EVOLUTION SINGLE BEGINING RNA WORLD CHILLY START DEEP SEA VENT COMMUNITY CLAY ELECTRIC SPARK

7. PRE-MODERN THEORIES THEORY OF SPECIAL CREATION Life formation on the earth have been taken place due to supernatural or divine forces. It has no scientific explanations. Hindu Concept - lord Brahma created the living world in one stroke. Christian and Islam Concept- God created this universe, plants, animals and human beings in about six days .

8. THEORY OF SPONTANEOUS ORIGIN Life may have evolved from non-living things, decaying and rotting matter like straw, mud etc. Hypothesis was generated by Aristotle. According to Aristotle, every living being is made up of a compound of matter and form. He believed that male semen and female matter (menstrual blood) were produced by bodies as a result of their proportions of heat, ingested food and were a byproduct of the elements earth and water.

9. THEORY OF BIOGENESIS Life comes from pre-existing life, “ Omnis vivum exovos” . In 1665, Redi’s Spallanzani and Pasteur’s experiment proved that all living things arise from other living things and are composed of minute cells. Italian scientist Francesco Redi, is the first to disprove spontaneous generation by conducting an experiment. He placed thoroughly cooked meat in three jars. one uncovered – maggots developed Covered with parchment – no maggots developed Covered with muslin – fly laid eggs over it.

10. John needham creates a rebuttal towards Redi’s results and followed by Spallanzani. Finally Louis Pasteur conducted an experiment. Pasteur sterilized two swan neck flasks and filled them with nutrients containing broth which will allow organisms to grow on it. The swan neck ensured that broth won’t be contaminated by outside air. No organism arose from the broth showing that living organisms cannot arise spontaneously. But when he broke one of the swan necks living organisms appeared in that one thus proving that organisms can come from pre-existing organisms.

11. THEORY OF EXTRATERRESTRIAL ORIGIN Given by Richter in 1865, and also known as theory of Panspermia. Primitive life had come to the earth as seed or spores from other heavenly bodies through meteorites.

12. MODERN THEORIES THEORY OF BIOCHEMICAL EVOLUTION Presented in the 1923 independently by A.I. O parin and later supported by J.B.S. Haldane in 1928. Life could have arisen through a long series of physico-chemical changes, first inorganic and then organic compounds in accordance with ever changing environmental conditions. It can be studied in three categories- Chemical evolution of life Biological evolution of life Cognogeny

13. Chemical Evolution of life Formation of simple inorganic molecules The atmosphere of primitive earth had various elements like hydrogen, oxygen, nitrogen etc. T hese free atoms combine to form molecules and simple inorganic compounds like ammonia, water vapour, HCN etc. 2. Formation of simple organic molecules The simple inorganic compounds formed in atmosphere interacted and combined to produced simple organic compounds such as simple sugars, purines, pyrimidines, amino acids etc. The source of energy – UV rays, lightening, radiations from radioactive rocks and heat of earth. Water bodies changed into a broth or premordial soup or prebiotic soup. Stanley Miller and Harold Urey tested this step by used an experimental set up to recreate what environmental conditions were believed to be like on early earth known as Urey Miller Experiment.

14. UREY MILLER EXPERIMENT Recreate what environmental conditions were believed to be like on early earth. Subjected methane, ammonia and hydrogen (in 2:1:1 ratio) and steam (coming from water boiling in small flask) to electric discharge(sparking) from electrodes in a large chamber for about a week. Various types of amino acids, purines and pyrimidines have generated in the U-tube at the base of the apparatus. Drawbacks By examining rocks dated to be 3.7 billion years old geologists determined that earth had an oxygenic atmosphere not rich in methane and ammonia. Oxygen is an oxidizing agent and would inhibit chemical evolution.

15. 3. Formation of complex organic molecules Simple organic compounds combined and recombined through the process of condensation, polymerization and oxido-reduction to form complex organic molecules like proteins, polysacchrides, peptides, polypeptides etc. in the primitive ocean. Synthesis of protein was the starting point for the origin of life. 4. Formation of complex biomolecules In due course of time nucleotides underwent polymerization to form nucleic acids- DNA and RNA in primitive ocean. Enzymes and coenzymes came into existence. Certain enzymatic proteins associate with nucleic acids forming nucleoproteins as self duplicating system.

16. Biological evolution of life 1. Formation of coacervates The complex organic molecules of premordial soup in ocean aggregated together through the colloidal system and bounded water layer were called coacervates which were presumed to formed in primitive water about 308 billion years ago. They are the intermediate between molecule and organism. 2. Formation of protocells Some of the coacervates having DNA and RNA evolved further and they developed lipoprotein membrane and enzyme mediated reactions. 3. Formation of first cell Protocells evolved into first true cell, the procaryotic unicell. They absorb organic molecules from outside for body building and energy.

17. 4. Development of autotrophs When supply of existing organic compounds was exhausted some of the early procaryotes might have evolved into autotrophs. They are capable of synthesizing their own organic compounds by chemosynthesis, hence chemoautotrophs. They develop the chlorophyll through which the autotrophs can prepare the food and oxygen evolved during this process which are started to accumulate in the atmosphere. Cognogeny With increased meant in number of photoautotrophs oxygen released in great extent in ocean and came into atmosphere, thus an oxidising type atmosphere has been formed. Procaryotes gradually modified to be adapted to the aerobic mode of respiration. Gradually many types of algae, fungi, protozoa and other organic living organisms developed.

18. DIAGRAMMATIC REPRESENTATION OF BIOCHEMICAL EVOLUTION OF LIFE

19. DEEP SEA HYDROTHERMAL VENT THORY The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents, spewing key hydrogen rich molecules. These rocky nooks may have concentrated molecules together and provided mineral catalysts for critical reactions. Today these vents, rich in chemical and thermal energy, sustain vibrant and strange non photosynthetic ecosystem.

20. RECENT DEVELOPMENT In April 2011, researchers in Italy found that if they mixed formamide, a simple chemical present in space, with material from a meteorite, and then heated the mixture, that they produced nucleic acids (building blocks of DNA and RNA), the amino acid glycine and a precursor to sugar. In February 2010 scientists at the Scripps Research Institute in San Diego announced that they synthesized RNA enzymes, known as ribozymes, that can replicate themselves without the help of any proteins or other cellular components. In May 2009, a team led by John Sutherland, a chemist at the University of Manchester in England discovered how the basic nucleotides of RNA could spontaneously assemble. He formed the RNA nucleotide

21. CONCLUSION All the evidence gathered thus far has revealed a great deal about the origin of life, but there is still much to learn. Because of the enormous length of time and the tremendous change that has occurred since then, much of the evidence relevant to origin has been lost. Most relevant theory regarding the origin of life is ‘Theory of Biochemical Evolution’ by Oparin and Haldane, because it is scientifically proven. But none of these theories is 100% correct. Research is going on to unravel the mystery of origin of life.

22. REFERENCES Jain, P.C. and Anantharaman, M.S.: Palaeontology (palaeobiology) evolution and Animal Distribution. Arora, P. Mohan; 3 rd Edition: Evolutionary Biology. https://www.thedailystar.net/science/7-theories-the-origin-life-77163 https://bioprinciples.biosci.gatech.edu/module-1-evolution/origin-of-life/ https://www.lkouniv.ac.in/site/writereaddata/siteContent/202004261258144367alka_maths_Theories_of_life.pdf

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