Ancient Theory, Abiogenesis , Biogenesis

Ancient Theory
Abiogenesis
Biogenesis
Origin of life
Evolution of Prokaryotic
Evolution of Eukaryotes
Modern theory
Evolution of modes of Nutrition

1. Ancient Theory Dr. Sonia Bajaj Assistant Professor Department of Zoology Shri Shankaracharya Mahavidyalaya ,Junwani ,Bhilai

2. Ancient Theory (Mythological Approach ) Theory of Abiogenesis

3. Cosmozoic theory Cosmozoic theory was given by Richter in 1865 and is also known as panspermia ( seed/ Spores ) theory.   Panspermia is a hypothetical theory which states that life exists throughout the universe . The theory believes that life is distributed in the form of microbes and amino acids by space dust, asteroids, meteoroids, comets, etc. life is originated in space, in spatial ices, and continuously distributed to the planets by comets and meteorites. The primitive bacteria arid other microorganisms "arrived" here as spores transported by meteorites. It was called cosmozoa or panspermia which were preserved inside meteorites (mass of matter from outer space). life is originated in space , in spatial ices, and continuously distributed to the planets by comets and meteorites. These meteorites struck the barren earth to release the cosmozoa and helped in development of various creatures . This theory failed to explain the origin of life on the planet , hence it is not accepted.

4. Three kinds of panspermia Litho : life is transported throughout space when an impact on one planet causes rocks to be sent into space, moving to other planets in different solar systems. (One solar system to other solar system) Ballistic: life is transported throughout space when an impact on one planet causes rocks to be sent into space, moving to other planets within the same solar system . ( One Planet to other Planet) Directed: life is spread to other planets by humans ( intentionally by extraterrestrial civilizations) with more advanced technology.

5. Theory of directed P anspermia It now seems unlikely that extraterrestrial living organisms could have reached the earth either as spores driven by the radiation pressure from another star or as living organisms imbedded in a meteorite. As an alternative to these nineteenth-century mechanisms, we have considered Directed Panspermia, the theory that organisms were deliberately transmitted to the earth by intelligent beings on another planet. We conclude that it is possible that life reached the earth in this way. T he scientific evidence is inadequate at the present time to say anything about the probability. We draw attention to the kinds of evidence that might throw additional light on the topic.

6. Theory of C atastrophism Catastrophism is the theory that the Earth has been affected in the past by sudden, short-lived, violent events , possibly worldwide in scope. The concept was first popularized by the early 19th-century French scientist Georges Cuvier . who proposed that new life forms had moved in from other areas after local floods, and avoided religious or metaphysical speculation in his scientific writings. Huge catastrophes caused major changes to Earth’s geology and biology in a short period of time . example:- worldwide flood in the days of Noah, the formation of a rocky mountain was due to an earthquake.

7. Theory of Spontaneous generation

8. Spontaneous generation is an obsolete theory which states that living organisms can originate from inanimate objects. The theory believed that dust created fleas , maggots arose from rotting meat, and bread or wheat left in a dark corner produced mice among others. Although the idea that living things originate from the non-living may seem ridiculous today. The theory of spontaneous generation was hotly debated for hundreds of years . During this time, many experiments were conducted to both prove and disprove the theory.

9. Experiments in Support of Spontaneous Generation The doctrine of spontaneous generation was coherently synthesized by Aristotle, who compiled and expanded the work of earlier natural philosophers and the various ancient explanations for the appearance of organisms , and was taken as scientific fact for two millennia. Aristotle The Greek philosopher Aristotle (384–322 BC ) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water.

10. John Needham The English naturalist John Turberville Needham was in support of the theory. Needham found that large numbers of organisms subsequently developed in prepared infusions of many different substances that had been exposed to intense heat in sealed tubes for 30 minutes. Assuming that such heat treatment must have killed any previous organisms, Needham explained the presence of the new population on the grounds of spontaneous generation. Experiments against Spontaneous Generation Though challenged in the 17th and 18th centuries by the experiments of Francesco Redi and Lazzaro Spallanzani , spontaneous generation was not disproved until the work of Louis Pasteur and John Tyndall in the mid-19th century.

11. Theory of Biogenesis

12. Francesco Redi’s Experiments: The Italian physician and poet Francesco Reid's was one of the first to question the spontaneous origin of living things . In this experiment, he selected two large and clean glass beakers . Place the same amount of meat into the beaker . The first beaker was kept open and t he second beaker was covered or closed with the lid. He placed the two beakers aside and left them undisturbed for a few days. Observation- After a few days, he observed that: In a first beaker , i.e. beaker without a lid, many maggots developed on meat, and flies were present in and around the first beaker. In a second beaker , i.e. beaker with a lid , there were neither maggots nor flies around the beaker. Result- This experiment disproved the idea of spontaneous generation for all living organisms, from smaller microbes to giant animals. . Redi’s successfully demonstrated that the maggots came from fly eggs .

13. Louis Pasteur Experiments: Louis Pasteur‘s 1859 experiment is widely seen as having settled the question of spontaneous generation. Pasteur selected several unique S-shaped flasks and divided them into two different sets. Pasteur prepared a Meat broth ( शोरबा ) . Pasteur added the prepared broth to the first set of S-shaped flasks, boiled it, and sealed the flasks with lids. Pasteur added the prepared broth to the second S-shaped flasks, boiled it, and uncovered it. Later, he placed both flasks (first and second) sets at different locations . Observation -After a few days, he observed that: He noticed the dust collected on the neck of the flasks. In the first set of flasks, there was no microbial growth, In the second set of flasks, there was microbial growth. Result- H e proved that microbes are present in the air but will not arise from the air or dust . In both sets of flasks, he used the same boiled broth , but the first set of flasks was sealed , and the second set was left open for microbes to enter, reproduce and multiply. This work was so conclusive ; that biology codified the “ Law of Biogenesis,” which states that life only comes from previously existing life.

14. Abiogenesis Biogenesis/ Autogenesis Abiogenesis refers to a theory on the origin of life, describing that the life originated from inorganic or inanimate. Biogenesis refers to a theory on the origin of life, describing that the life originated from pre- existing living matter. Substances Proposed by Alexander Oparin, Stanley Miller, and Harold Urey. Proposed by Theodore Schwann, Matthias Schleiden, and Rudolf Virchow. Sates that the life on earth is originated from Non –Living Compound. Sates that the life on earth is originated from the pre-existing living forms. Not scientifically proved. Proved by scientific experiments. Based on observations and national thoughts. Based on practical experiments and material evidence.

15. Modern Theory (Origin of Universe)

16. Big Bang T heory In 1927, an astronomer named  Georges Lemaître  had a big idea. The majority of scientists agreed that the universe was created with a gigantic explosion called the Big Bang. Astronomers explain the universe began as just a single point, then expanded and stretched to grow as large as it is right now—and it is still stretching! It suggests that through a process of expansion and explosion hydrogen gas was created which led to the formation of stars, and their death (supernova) led to the creation of life . or All of the energy in the universe was concentrated in an extremely small point (smaller than a subatomic particle such as a nucleus). With an explosion, the hot and dense tiny particle then gave birth to the present-day universe. It grew from smaller than the nucleus of an atom to bigger than a galaxy . The Big Bang characterized by an intense burst of energy is considered an event that is thought to have created our universe.

17. Origin of Solar System & the Earth Nebular Hypothesis Our solar system formed at the same time as our Sun as described in the nebular hypothesis . It is most commonly accepted hypothesis of origin of earth. It proposes that the earth is originated by gradual condensation of interstellar dust or cosmic dust termed as nebula . About 10000-20000 million years ago, a highly condensed mass of cosmic material was present termed as ylem that included of neutron, proton, and electron like particles. The explosion of cosmic material led to numerous pieces called nebula . According to nebular hypothesis in the beginning, it was a spinning ball of hot gases and vapours of elements. The spinning nebula collected the vast majority of material in its center, which is why the sun Accounts for over 99% of the mass in our solar system. The elements such as heavy metals Nickel, Iron, Zinc, etc , went to the centre to form the  core . Lighter elements as aluminium, silicon, sulphur etc , constituted mantle and crust of earth. The lightest and gaseous substances like hydrogen, helium, carbon, nitrogen, oxygen, formed atmosphere .

18. Solar System I billion years after the big bang galaxies was formed. The age of the Solar System and that of the planet Earth is approximately 4.54 billion year's old. This is based on the age of meteorites, which are believed to System have been formed the same time as the rest of the Solar System. 1. Encounter Hypothesis E ncounter hypothesis, about 5 Gya , a rouge star passed close to the sun and stripped materials (hot gases) from us both the sun and rouge star . The hot gases continued to span in the same direction as the sun , and coalesced into smaller humps which formed the planet. This explained how the planet was formed . T he first problem with this theory is that even though hot gases expand , they would not contract. So bese did the humps of hot gas contract to form planets .

19. 2. Protoplanet Hypothesis The Solar System began with a fragment from an interstellar cloud composed mainly of hydrogen, helium, and trace amounts of the light elements . The planet is differed in chemical composition , depending primarily on their initial distance from the sun as they formed. T he terrestrial planets formed near the central portion of the solar nebula, where the temperatures were high enough to vaporize all compounds in the dust except the high-temperature metallic and silicate minerals in the inner portion of the disk . T he outer disk which remained relatively cooler , allowing them to be rich in volatile, icy, and gaseous materials. The fragments of the interstellar cloud then formed the dense central region of the solar nebula, which collapsed more rapidly than its outlying parts. T he solar nebula, contracted, it rotated more rapidly, conserving its angular momentum . It also grew by accretion as material continued to fall inward from its surroundings. The solar nebula eventually evolved into the sun . Gravitational instabilities ruptured the thin disk into eddies, each containing many small particles which built up and accreted. T he accretion continued, larger asteroid-sized aggregates called planetisimals were formed, which orbited the center of the solar nebula. The planetisimals further grew in size due to the gravitational attraction they exerted on to one another, forming moon-sized bodies that would later become planets.

20. Biochemical origin of life Scientists now accept that it is not possible to create life spontaneously. Specific requirements for life’s appearance are essential. T.H. Huxley and John Tyndall asserted that inorganic chemicals could produce life . But as the knowledge of biochemistry was not available that time , their ideas were vagued. This idea was proposed by the Russian biochemist A.I.Oparin (1923 ) and with J.B.S. Haldane’s assistance. Oparin - Haldane theory is also called chemical theory naturalistic theory . In his book “The Origin of Life on Earth ” in1936, they offered an extensive description of the origin of life by evolution or chemicals . It is, thus, often called the Oparin and Haldane theory. According to this theory, through a series of chemical reactions around 4.2 billion years ago, life emerged in water on primitive earth from chemicals, thus called the biochemical theory of origin of life. Modern views regarding the origin of life include chemical evolution and biological evolution : Oparin classified his theory into following three steps . A. Chemogeny : Formation of organic compounds from inorganic substances . B . Biogeny: Formation of biological molecules . C . Cognogeny: Modifications of life .

21. Chemogeny ( i ) Formation of water, ammonia, methane and cyanide Earth was formed by the condensation and stratification of Ylem about 4.6 billion years ago . Primitive atmosphere had the elements like carbon, hydrogen, nitrogen and oxygen . They were in the gaseous state due to high temperature . H ₂ was most reactive element at that time. So it reacted with other elements to form various compounds. Due to the gradual decrease in temperature, they collided and combined to form molecules and compounds. Hydrogen combined with oxygen to form water . Free oxygen atoms were not available at that moment, so primitive atmosphere was of reducing type. Hydrogen also combined with nitrogen to form ammonia . These molecules were considered as key molecules in the origin of life . C + 2H₂ → CH4 (Methane ) 2H₂ +O₂ → 2H₂O (Water ) N ₂ +3H₂ → 2NH 3   (Ammonia ) 2C + N ₂ + H₂→ 2HCN (Hydrogen Cyanide)

22. (ii) Formation of hydrocarbons : With the further decrease in temperature of the earth up to 100°C or even low, highly reactive free radicals like -CH and - CH₂ , condensed, collided and formed varieties of saturated and unsaturated hydrocarbons . CH+CH → C ₂H₂ (Ethyne) [Unsaturated ] CH₂ + CH ₂ → C₂H₄ (Ethene) [Unsaturated ] CH₂ + CH ₂ → CH ₂ + C (Methane) [Saturated ] (iii) Formation of oxy and hydroxy derivatives of hydrocarbons: Above hydrocarbons reacted with steam and formed oxy and hydroxy derivatives of hydrocarbons ( such as aldehydes and ketones). C₂H₂ + H₂O → CH 3 CHO Above reactions were presumed to be taken place in the sea water that had organic compounds . The chemical reactions resulting into the formation of carbohydrates, amino-acids, fatty acids and other complex organic substances probably occurred in sea which is described as primordial or pre-biotic soup or hot dilute soup. CH₄ +H₂O➡ Sugars CH₄ + H₂O+NH₂ Amino acids It was described as 'hot dilute soup' or 'primordial soup '. It was also referred to as " warm little pond" by Darwin .

23. Sources of energy :- UV rays or light energy from sun . heat energy from volcanoes or high temperature of primitive earth . electric energy from lightening etc .

24. B. Biogeny (Formation of complex biomolecules )- Following chemogeny, the next step is biogeny . Biogeny refers to the formation of primitive life . It can be described under the following sub-steps . Formation of nucleic acids : It is assumed that sugar, phosphate and nitrogen bases combined to form nucleotides . Number of nucleotides combined to form DNA and RNA . The formation of nucleic acids (DNA and RNA) was a significant event as they were capable of self-duplication . They were considered as first sign of origin of life . DNA/RNA CH₄ + HCN + H₂O + NH 3   → Nitrogen bases (purines, pyrimidines ) Nitrogen bases + Pentose sugar + Phosphates → Nucleotides Nucleotides + Nucleotides → Nucleic acids (DNA and RNA )

25. ( II) Formation of Coacervates Due to intermolecular attraction, the complex organic compounds of primordial soup are collected to form large colloidal cells such as aggregates called coacervates or microsphere . T hey had the power of growth and break, such coacervates were efficient and multiplied. Coacervate formation is referred to as coacervation . (iii) Formation of primary organisms: Coacervates absorbed organic substances from the ocean and grew in size and multiplied and formed anaerobic chemo-heterotrophs / first cells / proto cells / probiont. Amino-acid, sugars, fatty acids and glycerol gave rise to polymers which may have assembled into spherical structures called proto- bionts . (by Oparin ) Proto-cells ( Protovirus-First living Cell)) were similar to viruses. They gave rise to prokaryotic and eukaryotic cells . Prokaryotic cells: Cells without membrane bounded cell organelles. Ex. Monera. It gave rise to bacteria and cyanobacteria (blue green algae ). Eukaryotic cells: Cells with membrane bounded cell organelles. Ex. Protista . It gave rise to protozoa, metazoa and metaphyta.

26. Cognogeny ( Modification of life) /Evolution of modes of Nutrition a . Origin of autotrophs Due to shortage of food in seas , organisms had to change their feeding habit and became parasitic, saprophytic, chemosynthesizers , photosynthesizers and so on . The first cells were anaerobic, prokaryotic and chemoheterotrophic. Later on, they changed into anaerobic, prokaryotic and chemoautotrophic (organisms using inorganic elements ). They were chemoautotrophs, such as nitrifying bacteria, sulphur bacteria, iron bacteria, etc. 6CO 2    + 12H 2 S → C 6 H 12 O 6  + 6H 2 O + 12S On further modification, they changed into anaerobic, prokaryoti c and photoautotrophic (able to synthesize food in sunlight). These phototrophs synthesized their food by photosynthesis utilizing water as raw material . Cyanobacteria was the first oxygenic and aerobic photoautotrophs that evolved about 2700 million years ago. 6CO 2 + 6H 2 O →  C 6 H 12 O 6  + 6O 2 They released O₂ to environment so aerobic organisms arose . Therefore, some prokaryotes changed into aerobic, eukaryotic, and photoautotrophic .

27. b. Origin of eukaryotes : True photosynthetic prokaryotes have shifted to aerobic respiration . Then cyanobacteria developed a true nucleus like prokaryotes and transformed into eukaryotes . It were like today’s unicellular species . Multicellular species have evolved from unicellular organisms via the colonization process . They formed into higher forms of metazoa and metaphyta . Evidences in support of origin of life: Miller- urey

28. Miller- Urey's experiment In 1953, Stanley Miller and his professor Harold C. Urey designed this experiment in favor of Oparin and Haldane's biochemical concept of origin of life . They did a series of experiments In the lab by creating the conditions that might have existed in the early primitive earth . Experiment :- They designed their apparatus of glass tubes and flasks as shown in figure . The apparatus possessed two glass chambers- water chamber and gas chamber . Water was boiled in the water chamber to promote steam circulation in the chamber . The gas chamber contained mixture of gases like methane, ammonia and hydrogen in the ratio of 2:2:1 . Energy was supplied in a closed chamber by heating, electric discharges of 60000 volts from electrodes, and UV . The condenser was used to cool down the mixture formed by passing the steam over the gases . The whole set up was run for a week . Observation: They noticed a condensed liquid with a dark colour . It was gathered and chromatographically analyzed , and the liquid was found to be a mixture of sugars, amino acids (glycine, analine , etc.) and fatty acids . Conclusion : The experimental results support the Oparin -Haldane theory of the origin of life that organic molecules are created from inorganic molecules during the course of the origin of life .

29. References Organic Evolution- N.Arumugam Invertebrate Zoology-N. Arumugam Invertebrate Zoology-Park Haswell & Williams