Origin Of Life In Volcanic Vents PDF

BY158 The Origin of Life Hydrothermal vents Dr. Corina Ciocan [email protected] Content Building blocks of life Big Bang theory Origin of life and chemical evolution Volcanic vents Photosynthesis and Chemosynthesis  Universe began with the Big Bang...

BY158 The Origin of Life Hydrothermal vents Dr. Corina Ciocan [email protected] Content Building blocks of life Big Bang theory Origin of life and chemical evolution Volcanic vents Photosynthesis and Chemosynthesis  Universe began with the Big Bang Earth about 5 billion years old View of Life arose on earth Most spontaneously Scientis Earliest life were bacteria (3.5 billion years ago) ts Genetic drift and natural selection pressures caused changes in genetics of populations Millions of species arose on earth over billions of years  Living organisms: Definition of life from ‘Life – The Science of Biology’ by Sadava et al. Biologists define ‘living things’ as all the diverse organisms descended from a single-celled ancestor that evolved almost 4 billion years ago. Because of their common ancestry, living organisms share many characteristics. Consist of one or more cells Contain genetic information Use genetic information to reproduce themselves Are genetically related and have evolved Can convert molecules obtained from their environment into new biological molecules Can extract energy from the environment and use it to do biological work Can regulate their internal environment  Building Blocks of Life Essential elements 118 (as per 2022) natural elements recognized à 25 essential to life ! BUT just four: carbon (C), oxygen (O), hydrogen (H) and nitrogen (N) make up 96% of living matter Remaining 4% comprise Phosphor (P), sulphur (S), calcium (Ca), potassium (K) and a few others (Element is a substance that cannot be broken down to other substances by chemical reactions )  Natural occurring elements in the multicellular organisms Symbol Element Atomic % of human body weight number Elements making up ~96% O Oxygen 8 65.0 C Carbon 6 18.5 H Hydrogen 1 9.5 N Nitrogen 7 3.3 Elements making up ~4% Ca Calcium 20 1.5 P Phosphorous 15 1.0 K Potassium 19 0.4 S Sulphur 16 0.3 Na Sodium 11 0.2 Cl Chlorine 17 0.2 Mg Magnesium 12 0.1 Elements making up less than 0.01% (trace elements) boron (B), chromium (Cr), cobalt (Co), copper (Cu), fluorine (F), iodine (I), iron (Fe), manganese (Mn), molybdenum (Mo), selenium (Se), silicon (Si), tin (Sn), vanadium (V), zinc (Zn)  Boron deficiency Nitrogen deficiency Magnesium deficiency Iodine deficiency  Building Blocks of Life The molecule that supports all of life à Water - Three quarter of earth’s surface is submerged in water – solid, liquid & gas - Life on earth began in water and evolved there - All living organisms require water - Most cells are surrounded by water - 70-95% cell content is water HOW / WHY is it so important?  cellular 50 - 90% water à source of protons, hydrogen and oxygen in photosynthesis and the solvent of biomolecules The major elements of covalently bound biomolecules are carbon, hydrogen, Life on nitrogen, oxygen, phosphorus and sulfur. There is a universal set of small molecules: (i.e. sugars, amino acids, Earth nucleotides, fatty acids, phospholipids, vitamins and coenzymes.) The principal macromolecules are proteins, lipids, carbohydrates and nucleic acids. There is a universal type of membrane structure (i.e. the lipid bilayer).  Fundamental Properties of Life cellular organization sensitivity growth development reproduction regulation homeostasis heredity  Universe is expanding. The Big Bang Theory states that approximately 8-12 billion years ago there was a cataclysmic explosion that caused the formation of the galaxies of the universe. Due to the explosion, the galaxies are moving apart Big from each other. Bang If we know the distance between galaxies and speed that the galaxies are Theory moving apart, we can back calculate when the universe began First estimate of the age of the universe was 20 billion years old https://www.youtube.com/watch?v=H dPzOWlLrbE  Big Bang Theory First, quarks clump together into protons and neutrons and then protons capture electrons to form Hydrogen atoms. The explosion of the Big Bang only formed Hydrogen and Helium. Later, Gravity pulls the Hydrogen and Helium together to form stars, and galaxies; Heavier elements (Carbon, Oxygen, etc) are formed inside stars ; Origin of Life: Earth began as a lifeless planet about 5 billion years ago Scientific Life arose on the planet spontaneously Hypothesis For life to form spontaneously… Primitive Earth’s chemicals had to combine to form organic molecules Organic molecules had to combine to form primitive cells (protocells) Primitive cells had to evolve into a true cells  Evidence that organic molecules could form spontaneously Dr. S. Miller & Dr. H. Urey created organic compounds (e.g. amino acids) using gasses and electricity (1953) Recent studies showed that primitive atmosphere did not contain ammonia, but oxygen!  Chemical evolution led to the formation of protocells Based on: Mader, S., Inquiry Into Life, McGraw-Hill  Clock Analogy in the history of life  Earliest Cells Microfossils have been found in rocks as old as 3.7 billion years old. – resemble prokaryotes (greek – “before nucleus”) lack nucleus of more complex eukaryotes Stromatolites – “colonies” of cyanobacteria  Estimates suggest that photosynthetic organisms appeared on Earth about 2.5 billion years ago. The original autotrophic organisms may have actually used hydrogen sulfide (H2S) as their electron source. Scientists then speculated that cyanobacteria evolved the ability to split a water molecule (H2O), which made the super-strong reducing agents needed for fixing carbon dioxide (CO2) and producing the carbohydrates required for life as we know it.  What Were the First Life Forms? Our ultimate relative was a single-cell, bacterium-like organism known as Last Universal Common Ancestor or Luca. And it could help establish how life on Earth began, at the very start. The findings could be a huge new contribution to arguments about how life actually got going on Earth. Researchers argue about whether life began somewhere extreme – like Luca’s apparent home near a deep sea vent – or whether it in fact began somewhere more pedestrian, like a small pond.  What Were the First Life Forms? Chemosynthesis – no oxygen – the first autotrophic cells did not use photosynthesis – These cells used chemosynthesis to produced food CO2 is used as the carbon source The energy comes from inorganic substances like sulfur – Archea are prokaryotic cells living today in harsh environments that used chemosynthesis  LUCA arrived about 3.7 billion years ago, and would eventually give rise to two simple cells: bacteria and archaea. Scientists are busy now to explore the 355 genes that appear to have originated in Luca and understand what they share. The organism appears to have lived in vents deep in the sea, where metallic, gassy plumes erupt from seawater that interacts with magma that comes up from the ocean floor. Article in Nature Microbiology, April 2016 – LUCA was “anaerobic, CO2-fixing, H2- dependent, N2-fixing and thermophilic”.  LUCA Although it is not known when or where life on Earth began, some of the earliest habitable environments may have been submarine-hydrothermal vents. Dodd et collab, 2017 Nature, describe putative fossilized microorganisms that are at least 3.8 bill and possibly 4.3 bill years old in ferruginous sedimentary rocks, interpreted as seafloor- hydrothermal vent-related precipitates, from the Nuvvuagittuq belt in Quebec, Canada.  First Eukaryotic Cells Eukaryotes probably arose about 1.5 bya. Internal membrane-bound structures such as mitochondria and chloroplasts are thought to have evolved via endosymbiosis. Energy-producing bacteria were engulfed by larger bacteria. à Beneficial symbiotic relationship Endosymbiosis  What is Endosymbiotic Theory? Evidence for Endosymbiont Theory – Mitochondria and chloroplasts have their own DNA https://www.youtube.com/watch?v=8oSqXAwLsZc&t Their DNA is circular, =102s similar to prokaryotic DNA – Mitochondria and chloroplasts have ribosomes similar to prokaryotic cells – Mitochondria and chloroplasts reproduce by binary fission, independent from the rest of the cell  Sexual reproduction First Eukaryotic cells can reproduce sexually, thus allowing for genetic recombination. Eukaryotic Genetic variation is the raw material necessary for evolution. Cells Multicellularity arisen many times among eukaryotes fosters specialization https://www.youtube.com/watch?v=qabl5eIba2g  Organic/inorganic Prokaryote/eukaryote Photosynthesis/Chemosynthesis Important terms Vertebrate/Invertebrate Unicellular/Multicellular Endosymbiosis  Evidence to this is provided by volcanic vent communities, where driving force is chemosynthesis, rather than photosynthesis. Compared to the surrounding sea floor, volcanic vent zones have a density of organisms 10,000 to 100,000 times greater. The hot springs and strange creatures were discovered by Alvin, the world's first deep-sea submersible, in 1977 at the Galapagos Rift. At about the same time, a Harvard graduate student proposed chemosynthetic bacteria that oxidize sulfides or elemental sulfur as a mechanism by which tube worms could survive near hydrothermal vents. The irony is that once scientists knew what to look for, they went to other well-known The discovery of ecosystems that were hydrothermal vents and rich in hydrogen No one had ever thought cold-water methane seeps sulfides, such as salt to look for them, but gave us a new vision of marshes, and found the these communities were primary production in the same mutualistic there all along. deep sea. association of chemosynthetic bacteria and animals that had stunned them in the deep vents. 2. Water which is vented out of the rock is hot (> 270 deg C), acidic, poor in oxygen but rich in metals leached from the basalt and rich in hydrogen sulphide. 1. Seawater circulates through hydrothermal cell and undergoes chemical reactions with the magma and basalt. Elements are exchanged between the seawater and the rock. 3. On exit, this reacts with cold, alkaline, oxygen-rich water and the metals precipitate as sulphides. Because most of the sulphide precipitates are black, the water leaving the vent turns into a black smoke -> "black smokers". White smokers also present (slightly cooler), plus lower temperature (2 to 23 deg C) warm vents.  Support fauna dominated by giant tube worms (up to 2.4m length) plus clams, mussels, crabs, shrimps, snails and fishes (detritus or filter feeders) Temperature regulates zonation http://ocean.si.edu/ocean- videos/hydrothermal-vent-creatures How do these large heterotrophs satisfy their food requirements? Base of the food chain in vent communities is occupied by chemosynthetic bacteria rather than plants. Anaerobic bacteria present at the vents oxidise the gas H2S to form sulphur compounds – chemical energy released is used to satisfy their metabolic requirements. Other organisms then feed on these bacteria….. Tube worms host the bacteria within their body in a symbiotic relationship. See: http://www.csa.com/discoveryguides /vent/review.pdf for further details. Photosynthesis : All photosynthetic organisms use solar energy to turn carbon dioxide and water into sugar and oxygen. There is only one photosynthetic formula: CO2 + 6H2O -> C6H12O6 + 6O2. Chemosynthesis: The use of energy released by inorganic chemical reactions to produce food. Chemosynthesis is sustaining life in absolute darkness, where sunlight does not penetrate. All chemosynthetic organisms use the energy released by chemical reactions to make a sugar, but different species use different pathways. CO2 + 4H2S + O2 -> CH20 + 4S + 3H2O. The evolution to water-driven photosynthesis must have required a lot of changes in how organisms at the time conducted photosynthesis. The main reason for the needed changes is that H2O holds onto its electrons a lot better than H2S does. Once organisms figured out how to pull H2O into the reaction, a lot of oxygen (O2) was pumped into the atmosphere, and organic materials began to accumulate on the young Earth. The production of O2 is a fantastically wonderful step forward for life on Earth, but O2 in the atmosphere actually created a problem for early life forms. O2 is a great oxidizing agent, meaning that it can pull electrons away from other biological compounds in the cell. The gradual increase in O2 in the atmosphere provided a means of selection.