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Transcript
Origin of Life From spontaneous generation to biogenesis Spontaneous Generation • Spontaneous Generation-the long-held belief that living things could suddenly exist if the right combination of non-living objects were brought together in one place. • Seemed to be supported by the religious beliefs of the time. • Before 1800’s • Ex: wooden box + cloth + wheat = rats Francesco Redi (1626-1697) • Italian scientist who documented the life cycle of the fly. • Challenged the belief that flies spontaneously arose from rotting meat. • Hypothesis: If adult flies are kept away from rotting meat then new flies will not develop because maggots come from adult flies. Redi’s Experiment Experimental Control Maggots No Maggots Redi’s supported hypothesis was a major blow to the supporters of spontaneous generation, but… Lazzaro Spallanzani (1729-1799) • The invention of the microscope lead to speculation that a “vital force” caused bacteria and protists to spontaneously appear in liquids. • Spallanzani- Italian scientist who designed an experiment to test the hypothesis that microorganisms come from existing microorganisms and not a “vital force”. • Hypothesis: If boiled meat broth is sealed to keep out airborne microorganisms then new microorganism will not develop and spoil the broth because microbes in the air cannot land in the broth. Spallanzani’s Experiment Control Experimental Spallanzani’s results supported his hypothesis but.. supporters of spontaneous generation objected that he had “destroyed” the vital force of the air inside the flasks by boiling them. Spontaneous generation continued to be the preferred explanation for another 100 years. Louis Pasteur (1822-1895) • Paris Academy of Science offered a prize to anyone who could conclusively clear-up the spontaneous generation controversy. And the winner is… • Pasteur- French scientist who showed organisms in the air lead to the spoilage of food. Also described the process of fermentation and invented the pasteurization of milk. • Hypothesis: If boiled meat broth is kept in a container that is open to the air but traps airborne particles then new microorganism will not develop and spoil the broth because microbes in the air cannot land in the broth. Pasteur’s Experiment Swan neck Control Broth boiled Experimental Broth cooled, sits for 1 year Broth spoils one day after neck is broken off Out with Spontaneous Generation… ..Hello Biogenesis Spontaneous Generation: Belief in the transformation of non-living to living. Biogenesis: Supported theory that all living things are derived from living things. Origin of Life How did life begin? 1. Creation A. A divine supernatural being must have created life on Earth because it is just too complicated to have happened randomly. B. A superior intellect (way smarter than us!) must have created life on Earth because it is just too complicated to have happened randomly. 2. Extraterrestrial Origin- life began on another planet from an older planetary system and was transferred to Earth on a meteorite. 3. Origin from simple inorganic compounds life arose from inorganic compounds brought together by the special conditions of the Early Earth Formation of Earth • Most planets have surfaces that are either toxic, too hot, too cold, or fluctuate too dramatically between hot and cold. • Our solar system is approximately 5 billion years old, with the first 400 million being the actual formation of planets from interstellar dust. • When the earth first cooled, volcanic activity caused high amounts of hydrogen, methane, and ammonia. • Oldest fossils are almost 3.5 billion years old Radioactive Dating • Many elements have radioactive Isotope Half-life (years) isotope forms that can be detected. C14 5,730 • When rock solidified or the body of an organism forms, a certain Th230 75,000 amount of radioactive Carbon, 1,300,000,000 Thorium, Potassium, or Uranium K40 becomes trapped. 238 U 4,500,000,000 • All radioactive elements naturally decay and turn into their nonradioactive forms (C14àC12) •The time it takes for ½ of the radioactive isotope content of a sample to decay is called the HALF-LIFE. •By measuring how much of a certain radioactive isotope is left, we can estimate the age of an object. The lower the amount of radiation, the older it is. Simulation Card Activity: First Conditions on Earth • Obtain a deck of cards for your group • Deal three cards and try to make one of the following combinations: NH2-CH2-COOH, CH3COOH, or CH3-CH2-COOH • Record your results on the data sheet provided for this activity. Repeat this 19 times. • Count the number of molecules you were able to form. Then, calculate the probability of forming a molecule with each deal. 15 Stanley Miller (1930& Harold C. Urey (1893-1981) •Urey and his student Stanley Miller built an apparatus capable of simulating the conditions of early Earth. evaporating____________ ocean •Warm water vapor that simulated__________ ___________ was created by a flask of boiling water. water •The vapor then passed through a reaction chamber where a mixture of hydrogen methane ammonia were combined with the ___________, _____________, and ___________ vapor. •Electrodes then electrified the steamy mixture in the reaction vessel to provide energy for the formation of new chemical _________. bonds gas •The vapor next passed through a condenser to change the ________ to a liquid. •The liquid was then collected and analyzed. •Complex biomolecules including: amino acids, ATP, and Nucleotides were produced. Jean Baptiste de Lamarck (1744-1829) • One of the first to suggest that the species we have on Earth today may have descended from a common ancestor. • Studied a collection of fossilized invertebrates and observed that many of them shared common physical traits. • Hypothesized that acquired traits were passed on to offspring from parents. • Acquired Traits were believed to be the result of learned behaviors or experiences and not by genes. • Lamarck believed that the giraffe’s neck is longer because the parent’s necks grew longer during a lifetime of trying to reach high leaves and that this new feature was passed to the next generation. • By this logic, removing a person’s appendix should result in… Evolution by Natural Selection Alfred Wallace (1823-1913) Charles Darwin (1809-1882) • Wallace and Darwin independently proposed the hypothesis that species are modified by natural selection. • Traits are not acquired but are selected for by environmental conditions. • Darwin most known because The Origin of Species was published by Darwin shortly after he and Wallace published their papers. Charles Darwin (1809-1882) • First to realize that in the same way humans use artificial selection to create new breeds of dogs and other domestic animals, nature must somehow be selecting for the creation of new species in the wild. • Collected most of his data as a naturalist studying the fossils and living specimens from South America. HMS Beagle •5 year mapping and collection voyage of the coast of South America and the South Pacific Darwin’s Theories 1. Descent with Modification • • Newer organisms in the fossil record are actually the descendents of older species. All species alive today descended from one or a few original types of life. Galapagos Island Finches Darwin’s Theories 2. Modification by Natural Selection • All living things have the potential to produce more offspring than the World can support, but growth is controlled by the “cruelty of nature”. • Because no two organisms (resulting from sexual reproduction) are identical, environmental pressures will lead to the survival of the few offspring that happen to be born with slightly more useful features. Darwin’s Theories • Therefore, Natural Selection is the mechanism that drives the process of evolution. • It can take MANY generations for evolutionary change to occur 24 Evolutionary Example: Bacteria You Watch At this have So… point a bacterial what 95% happens infection of the You stop after bacteria that taking is taking your has the causing been first antibiotics killed doses you and toof youneed your feel so medication antibiotics much better Your bacteria have evolved! Now But the you are few sick all over bacteria again and that the remained antibiotic will andnot were be productive resistant this starttime to reproduce 25 Terms – Just to be clear! • Evolution – the change of populations of organisms over generations • Natural Selection – the process by which organisms with favorable characteristics reproduce at higher rates than those without them; the mechanism for evolution • Artificial Selection – the breeding of organisms by humans for specific characteristics; often produces new breeds 26 Terms • Fitness: the ability of an individual organism to produce fertile offspring – An individual with high fitness is well adapted to its environment and reproduces successfully • Adaptations: favorable traits that give an organism an advantage in its environment and enhance its fitness • Vestigial Structures: features that were useful to an ancestor but not to the modern organism that has them (ex – Dorudon) 27 Homologous Structures • Homologous structures: similar features that originated in a shared ancestor. http://www.fsteeman.dds.nl/fossiel/tussenvormen.html Ichthyostega 360-370 mya Analogous Structures • Analogous Structures: features with identical functions and look similar, but with no anatomical or embryological similarity 29 Similarities in Embryology • In the early stages of development, all vertebrate embryos are similar, but those similarities fade as development proceeds. Similarities in Genetics • Scientists in the new field of genomics can look at the entire genome of organisms (their DNA in computer code) and see how similar the nucleotides are from one species to another. Patterns of Evolution • Coevolution – the change of two or more species in close association with one another – Ex – plant and pollinator – Madagascar orchid and Madagascan sphinx moth 32 Patterns of Evolution • Convergent Evolution – when the environment selects similar characteristics even though the ancestral types were quite different – Ex – Shark and Whale Patterns of Evolution • Divergent Evolution – two or more related populations become more and more dissimilar, usually in response to habitat change – Ex – Galapagos Island Finches