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Evolution FYOS Lecture 4 C and H2O for alien life! Common characteristics of Life Biologists have identified at least six key features that appear to be shared by nearly all of living organisms on Earth. o Order o Reproduction o Growth and Development o Energy Utilization o Response o Evolutionary Adaptation Characteristics of Life • Order • Reproduction • Growth and Development • Energy Utilization • Response • Evolutionary Adaptation Biologists have identified at least six key features that appear to be shared by nearly all of living organisms on Earth. Order : all living organisms exhibit order in their internal structure. molecules in living cells are not scattered randomly but instead arranged in specific patterns to make cell structures. Characteristics of Life • Order • Reproduction • Growth and Development • Energy Utilization Biologists have identified at least six key features that appear to be shared by most or all of living organisms on Earth. Order : all living organisms exhibit order in their internal structure. However, snow flakes, for example, show remarkable structures also. • Response • Evolutionary Adaptation But, snow flakes are not alive! Characteristics of Life • Order • Reproduction • Growth and Development • Energy Utilization Biologists have identified at least six key features that appear to be shared by most or all of living organisms on Earth. Order : all living organisms exhibit order in their internal structure. How about galaxies? Are they alive? • Response • Evolutionary Adaptation Therefore, “order” is not sufficient condition for life. But, it is a necessary condition. Characteristics of Life Reproduction: Organisms reproduce their own kind • Order • Reproduction • Growth and Development • Energy Utilization • Response • Evolutionary Adaptation A single-celled organism (an amoeba) copying its genetic material (DNA) and dividing into two genetically identical cells. Mule, Tigon, Liger, Computer virus? Again, necessary condition, not sufficient! Characteristics of Life • Order • Growth and Development : Living organisms grow and develop in patterns determined at least by heredity Growing embryos of Costa Rican frog • Reproduction • Growth and Development Heredity : passing on characteristics from one generation to next • Energy Utilization • Response • Evolutionary Adaptation Wild fires, crystal? Again, necessary condition, not sufficient! Characteristics of Life • Energy Utilization: Living organisms use energy to fuel their activities • Order • Reproduction • Growth and Development • Energy Utilization Tube worms near a deep sea volcanic vent. • Response Car? • Evolutionary Adaptation Again, necessary condition, not sufficient! Characteristics of Life • Order • Reproduction • Growth and Development • Response: Living organisms actively responds to changes in its surroundings A blacktail jackrabbit’s ears flush with blood, the blood automatically adjusted to maintain a constant internal temperature • Energy Utilization • Response • Evolutionary Adaptation Mercury in a thermometer? Again, necessary condition, not sufficient! Characteristics of Life • Evolutionary Adaptation: Life evolves in a way to become adapted to its surrounding white-tail ptarmigan • Order • Reproduction • Growth and Development Camo-moth • Energy Utilization • Response • Evolutionary Adaptation counter example? Evolutionary Adaptation • Charles Darwin (1858) 2 undeniable facts an inescapable conclusion Overproduction struggle for survival Individual variation Natural Selection Heritable traits that enhance survival and reproduction will become progressively more common in succeeding generations! An imaginary population of beetles of mixed color evolves into dark beetles. DNA is the backbone of the Evolution! Replicating the whole ~3 billion bases for human DNA takes only a few hours About 1 wrong coupling in every ~1 billion bases! Sickle-cell disease • Just one base change in one gene (Adenine Thymine) • Most mutations are harmful, but occasional good mutations are being picked up by “natural selection” • About 1 replication error in billion chances Mutation • Any change in the base sequence of DNA o o o o wrong base deleted base extra base etc. • Most of these errors have no effect Why? about 95% of human DNA bases are “noncoding DNA” Most significant change is from “deleted base”. • Due to this “error”, every individual living organism differ each other. • Mutation = molecular engine of the evolutionary adaption! How did all these start in the beginning? Organic Building Blocks Miller-Urey Experiment Experiment to create amino acids (1953) methane hydrogen water ammonia the first experiment to test the theory about the evolution of prebiotic chemicals and the origin of life on Earth. How did the DNA world get started? • Human DNA contains about 12 billion molecules • even a primitive virus has about 1 million molecules • many viruses use RNA instead of DNA as their genetic material DNA from the start? • Typical RNAs have 20-30 nucleotides… • Some RNAs are known to be self-replicable • RNAs are sufficiently simple so that several types of them could have been created by “Miller-Urey”-type reactions. • These RNAs were exposed to the natural selection Pre-cells • Molecular evolution would have been much more efficient if RNA and other molecules are confined in a structure. o Increasing the rate of reaction o Isolating its content to facilitate natural selection among RNA molecules! If no such enclosure, enzyme created by the best RNA can help other RNAs. Left: microscopic spheres made by cooling a warm solution of amino acids Right : microscopic membranes made from lipids mixed with water (instantaneously formed!) RNA cell? Lipid pre-cell can form on the surface of clay! + Very high chance of making RNA on the surface of clay with membrane!! • Right: lab experiment shows RNA strands (red) entrapped within a lipid pre-cell (green circle) made on the surface of clay! Chemistry on the early Earth 6 Presentations on Feb 15 • Convergent evolution o R. Shrestha o J. Hedley • Human Evolution o E. Clendening o A. Breeden • Panspermia o Z. Rindik o C. Starlcup