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Western University
Biology 1001A
Tom Haffie

Biology 182013 64300 PM Origins of Life pg5159 What is LifeAll life is composed of cellsthe fundamental unit of all lifeThe types of elements and atoms found in living things are also found in nonliving forms of matter as well living cells obey the same fundamental laws of physics and chemistry as abiotic thingsThe 7 characteristics of life 1 Display order all things are arranged in a highly ordered manner with the cell being the fundamental unit 2 Harness and utilize energy use and acquire energy from environment3 Reproduce 4 Respond to stimuli organisms can make adjustments to their structure function and behavior in response to external environmental changes 5 Exhibit homeostasis organisms are able to regulate internal environments and control them to main relatively constant 6 Growth and development 7 Evolve populations of living organisms change over time to become better adapted to environmentsProperties are emergenteach characteristic of life reflects a remarkable complexity resulting from a hierarchy of interactions that begins with atoms and progresses to molecules to macromolecules to cellsProperties are emergent because they come about or emerge from many simpler interactions o Example the ability to harness and utilize energy is not a property of molecules or proteins or biological membranes in isolation but instead are a product of all 3 working together where this property emerges from Earth Stats Universe formed 15 billion years ago Galaxies formed from stars dust and gasThe earth is 46 billion years old and areas in the solar system that harborwater are known as habitable zonesOldest Fossils 35 billion years agoEukaryotic fossils 22 billion years agoAll forms of life are composed of nucleic acids proteins lipids and carbohydratesPanspermia Is the hypothesis that life exists throughout the universe distributed by meteoroids asteroids and comets which brought organic matter to Earth ALH84001 Origin was Mars Polycyclic aromatic hydrocarbonsformed when microorganisms dieSpontaneous Generation Living matter cannot generate spontaneously from nonliving matterLouis Pasteur in 1859 Conditions much different on early Earth First cells arose where there had been no life before C e l lT h e o r y 1 All organisms composed of one or more cells 2 The cell is the smallest unit that has all the properties of life 3 Cells arise only from the growth and division of preexisting cellsEarly AtmosphereReducing atmosphereNo free oxygen O2Free hydrogen H2 and hydrides CH4 NH3 and H2OEnergy electric discharge in storms or solar energy no ozone layerThe Earths surface temperature probably hotter than todayMajor hypothesis of how molecules were formed with the absence of life Hypothesis 1 Reducing AtmospherePrimordial atmosphere probably contained hydrogen carbon dioxide ammonia and methane but lacked oxygen then that atmosphere became a reducing atmosphere where the molecules came into reactions with one another to yield larger more complex organic moleculesCompared to the proposed oxidizing atmosphere theory is that there was an abundance of oxygen which oxidized and accepted electrons to form organic molecules and water and also acted as the ozone layer but in a primordial atmosphere there was no ozone layer so ultra violet could reach the earth and catalyze reactionsHypothesis 2 Deep Sea VentsNutrient rich vents deep in the sea with reduced molecules that were present in primitive atmosphereHypothesis 2 Extraterrestrial OriginThe idea that the significant molecule for life came from space as many meteorites contain biologically important moleculesMillerUrey Experiment The MillerUrey experiment established that the conditions that existed in Earths primitive atmosphere were sufficient to produce amino acids the subunits of proteins comprising and required by living organisms In essence the MillerUrey experiment fundamentally established that Earths primitive atmosphere was capable of producing the building blocks of life from inorganic materials OBTAINED UreaAmino acidsLactic formic and acetic acidsnucleotidesLife Requires the Synthesis of Polymers Primordial Earth contained very little oxygentherefore complex organic molecules must have existed much laterAmino acids and nucleotiedes are monomers which are simpler and easier to synthesize than the key chemical components of life such as nucleic acids and proteins which are polymersmacromolecules formed from bonding together of individual monomers
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