PREBIOTIC ENVIRONMENT- Phytogeography and Evolution

The ppt on Prebiotic environment helps to understand the history of how the Earth was formed. According to various scientists , with respect to different theories . Also helps to learn how the life started existing on earth.

1. Subject : PHYTOGEOGRAPHY & EVOLUTION Topic : PREBIOTIC ENVIRONMENT for M.Sc. BOTANY students

2. INDEX Introduction Conditions of the Prebiotic Environment Interesting facts about Prebiotic Environment Theory of Special Creation Cosmozoic Theory (Panspermia theory) Theory of spontaneous generation / Theory of Abiogenesis Theory of Biogenesis Chill y Start Theory Hydrothermal Vents Theory of simple Beginnings Theory of Biochemical evolution Reference

3. INTRODUCTION The prebiotic atmosphere is the 2 nd atmosphere present on Earth before today’s biotic ,oxygen rich 3 rd atmosphere, & after the 1 st atmosphere of Earth’s formation .The formation of Earth roughly 4.5 billion yrs ago , involved multiple collisions & coalescence of planetary embryos .This was followed by a <100 million year period on Earth where a magma ocean was present, the atmosphere was mainly steam, and surface temperatures reached up to 8,000 K(14,000°F).Earth's surface then cooled and the atmosphere stabilized, establishing the prebiotic atmosphere. The environmental conditions during this time period were quite different from today: the Sun was ~30% dimmer overall yet brighter at ultraviolet and x-ray wavelengths, there was a liquid ocean, it is unknown if there were continents but oceanic islands were likely, Prebiotic environment : Prebiotic environment refers to the environment before life , describing ideas about how life began from a ‘Prebiotic soup ’.

4. Earth's interior chemistry (and thus, volcanic activity) was different, and there was a larger flux of impactors (e.g. comets and asteroids) hitting Earth's surface Studies have attempted to constrain the composition and nature of the prebiotic atmosphere by analysing geochemical data and using theoretical models that include our knowledge of the early Earth environment. These studies indicate that the prebiotic atmosphere likely contained more carbon dioxide than the modern Earth, had nitrogen within a factor of 2 of the modern levels, and had vanishingly low amounts of oxygen. The atmospheric chemistry is believed to have been "weakly reduced", where reduced gases like CH4, NH3, and hydrogen were present in small quantities. The composition of the prebiotic atmosphere was likely periodically altered by impactors, which may have temporarily caused the atmosphere to have been "strongly reduced".

5. Constraining the composition of the prebiotic atmosphere is key to understanding the origin of life, as it may facilitate or inhibit certain chemical reactions on Earth's surface believed to be important for the formation of the first living organism. Life on Earth originated and began modifying the atmosphere at least 3.5 billion years ago and possibly much earlier, which marks the end of the prebiotic atmosphere.

6. Conditions of the Prebiotic Earth Earth’s early atmosphere probably contained hydrogen cyanide , carbon di oxide, carbon monoxide, nitrogen, hydrogen sulphide & water. Volcanic activity probably formed it .Released great amounts of water vapour that later condensed to form oceans. Released carbon dioxide that warms the atmosphere by absorbing outgoing heat .

7. 4. A common theme is that the ingredients for life were generated by the flow of energy (sunlight, lightning/ thermal radiation) through the primordial hydrosphere so that the putative mechanisms for the origin of life should be compatible with the conditions that would have prevailed in the early atmosphere & oceans .

8. It is believed that the universe came into existence with a single Titanic explosion called big bang about 15000 million years ago The fragments of the fire ball expanded & cooled to give rise to many celestial bodies which resulted in the formation of Solar system consisting of sun & the 8 planets Interesting Facts about Prebiotic Environment

9. 3 . Origin of life on earth is also known as Protobiogenesis . 4. It was also believed that life came into existence from non living substances of primordial earth about 3 billion years ago.

10. Theory of Special Creation A Spanish monk Father “Suarez” . He believed that the whole life on the earth was formed only in 6 days & according to this theory , all the living beings on earth were created by God or by some super natural power.

11. Cosmozoic Theory – Panspermia Theory “Panspermia” in Greek refers to “Seeds everywhere”. The Panspermia hypothesis states that the seeds of life exists all over the universe & can be propagated through space from one location to another. According to this Hypothesis, seeds of life travels through Asteroids, Meteorites & Comets .

12. Litho Panspermia : Transfer of seeds of life from one planet’s surface to another solar system. Ex :- During explosions / by Meteorites (some of these carry amino acids & Carbon inside the rocks . Ballistic Panspermia : Transfer of seeds of life from one planet to another but with in the same solar system. Ex :- Intentional / Directed Panspermia: living beings transfer the seeds of life Evidence : Some microorganisms can survive in harsh environment conditions such as UV radiations ,Proton Bombardment ,Cold Temperature, High Temperature , Extreme Pressure, Even in vacuum .... Ex: Bacterial spores can remain visible for up to 250 million years can be able to survive in vacuum . Types of Panspermia Tardigrade

13. History of Panspermia The 1 st known concept was written by Greek philosopher Anaxagoras around 500 BC - all things have existed from the beginning In 1743 French Natural historian Benoit de Maillet ,who believed“ seeded” by germs from space into the ocean . In 1973, Prof. Francis crick & Leslie Orgel proposed directed Panspermia hypothesis In 2000, Astronomer Chandra Wickramasingha presented evidence from samples of space contained clumps of living cells & light rays from the space . In 2001, Geologist Bruno & molecular biologist Giuseppe found bacteria inside a meteorite estimated to be over 4.5 billion years old In 2008, Stephen Hawking discussed about life in space .

14. Why is this Hypothesis Important....? Knowing history is always important for planning our future. If life came from space, there is a probability of civilized earth like planets in space could exist If space have beneficial organisms, we can use them . If they are dangerous, we can make solutions to avoid them .

15. Theory of spontaneous generation In 1668 , Francesco Redi, an Italian physician, did an experiment with flies & wide mouth jars containing meat. He took rotting meat pieces in jars. He sealed some of these jars tightly & other left open. After few days maggots (larval stage of an insect) appeared in open jars in which the flies went freely in & out & laid their eggs on meat. But in sealed jar in which the flies could not enter, did not show any maggots. Redi concluded that the maggots arise from the eggs laid down by the parent flies & that the maggots can not appear spontaneously. Redi set up new experiment in which he covered jars with fine muslin cloth of sealing them tightly & allowed free air in & out of the jars. After some time maggots appeared only in some jars. Redi concluded that free air is considered as vital force i.e; necessary for spontaneous origin. By 1745 an England Scientist John Needham used microscopic observations to support the theory of abiogenesis (Theory of spontaneous generation).

16. To test the theory he boiled meat broth for several minutes in a loosely sealed flask (allowed to cool the flask) . Immediately after boiling he saw under the microscope that the broth had no living things. After a few days he examined the flask & found microorganism. He concluded that the organisms originated spontaneously from the nutrient fluids.

17. Theory of Biogenesis Biogenesis is the formation (production) of new living organisms/ organelles. According to the theory of Biogenesis. Living things come from other living things, by means of reproduction i.e; life doesn’t arise spontaneously from non living material (or) it can also be stated as that everything came from a pre existing living thing. In 1668 Francisco Redi ,proved that no maggots appeared in meat when flies were prevented from laying eggs. In 1768 ,Lazzaro spallanzani demonstrated that microbes were present in the air & could be killed by boiling. In 1861,Louis Pasteur performed a series of experiments using Swan necked flask ,he kept microbes out but let air in by this he concluded that organisms such as bacteria & fungi do not spontaneously appear in sterile Nutrient rich media so,the life comes from pre existing life i.e Biogenesis.

18. Lazzaro Spallanzani’s Experiment Louis Pasteur ’s Experiment

19. Chilly Start Theory According to this theory about 3 billion yrs ago before the existence of earth, it is believed that only ice had covered the whole earth. The ice protected the organic molecules underneath the ocean reacted to form cells (Prokaryotes). Hydrothermal Vents Hydrothermal vents act as natural plumbing systems that transport heat and chemicals from the interior of the Earth and that help regulate global ocean chemistry. In the process, they accumulate vast amounts of potentially valuable minerals on the seafloor. Protons are the stepping stone for life existence . Protons were released by thermophiles .Chemoautotrophs converts the chemicals that had released from volcanic eruption to alkaline. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspots

20. NOTE : Scientists first discovered hydrothermal vents in 1977 while exploring an oceanic spreading ridge near the Galapagos Islands. Chill y Start Theory Hydrothermal Vents

21. According to this theory instead of originating from complex molecules like RNA & DNA ,life might have begun with small & simple molecules interacting with each other in cycles of reactions .These reactions might have been changed a single capsule to cell membranes & over time more complex molecules / cells. This is the most simple of the standing theories, and is difficult to dismiss. Theory of Simple Beginnings

22. Theory of Biochemical evolution Introduction : This Theory was proposed by Alexander Oparin in 1924 and J.B.S Haldane in the year 1929 , According to this theory life evolved from oceans during a period when the atmosphere was reducing no free oxygen while containing hydrogen, water , ammonia , methane & Carbon di oxide. Forces such as lightning, electric discharge such as sun ,wind UV light & Meteorites created organic molecules in atmosphere which rained into ocean. NOTE : Oparin reason out that oxygen prevents the synthesis of certain organic compounds that are necessary building blocks for evolution of life

23. Formation of Simple Inorganic Compounds: Primitive earth was very hot & few gases like Carbon, Hydrogen, Nitrogen, Helium were present. These gases reacted with each other because of warmth ,light ,etc & formed simple inorganic compounds like Hydrogen cyanide, water vapour & Ammonia . Formation of Simple Organic compounds : The simple inorganic compounds combined to form simple organic compounds like Purines , Pyrimidines, Amino acids , Sugars . Formation of Complex Organic Compounds : The simple inorganic compounds combined to form Nucleic acids, carbohydrates, proteins ,lipids fatty acids ,etc. According to this theory the evolution was as follows:

24. 4. Biological Evolution: Formation of life initiated from the ocean containing organic compounds Coacervates – Coacervates are the intermediates between molecule & living organisms. Lipids and proteins from the primordial soup formed droplets , cell membrane. These started exchanging also absorbing the nutrients from the ocean water, some protein started catalyzing reactions, gradually nucleic acids started replicating & further these coacervates reproduced by budding / by binary fission. Origin of Primary Living Organism – The coacervates presumably obtained energy by fermentation from the oceanic soup. They were anaerobes. They depended on the existing organic molecules for their nutrition.

25. Origin of autotrophs – These autotrophs utilized oceanic inorganic compounds to prepare their own food, so this process is known as chemosynthesis and the organism is chemoautotrophs. Cognogeny – With gradual increase in heterotrophs as they consumed nutrients of the ocean ,there was reduction in organic nutrients so, these organisms searched for alternative source. During photosynthesis, solar energy was trapped by light trapping pigment called chlorophyll. In this way several other organisms evolved (prokaryotic, anaerobic etc.). With the increase meant in number of photoautotrophs O2 released in great extent in ocean and came into atmosphere. Now an oxidising type atmosphere has been formed. Then prokaryotes gradually modified to be adapted to the aerobic mode of respiration. Gradually many types of algae, fungi, protozoa and other organic living organisms were developed.

26. References https://www.slideshare.net/HarinathaReddyA/biogenesis-242675866 https://www.slideshare.net/anirudh1993123/spontaneous-generation-anirudh-g-patil https://www.slideshare.net/SashikaDilshan1/panspermia-theory https://www.slideshare.net/nasirshaikh5/origin-and-evolution-of-life https://en.m.wikipedia.org/wiki/Prebiotic_atmosphere#:~:text=The%20prebiotic%20atmosphere%20can%20supply,in%20the%20Miller%2DUrey%20experiment https://www.slideshare.net/peteregorov71/origin-of-life-85982826 https://www.slideshare.net/alizayshehzad/prebiotic-evolution-118451390 https://www.lkouniv.ac.in

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