Mastering Biology: MBPOLLOCK01639 (not graded)Quizzes on MoodleThree Domains of Life:BacteriaArchaeaEukaryoteGo back in time no EukaryotesGo back further no archaea3.8-4 billion years ago nothing (chemical traces)No theory to describe how life came about only hypothesesSeveral possible explanationsOctums razar- simplest explanation is the most likelyEarth is 4.6 billion years old (know because of the moon)Difference between hypothesis and theoryHistory of Life on EarthThe experiment of Miller and Urey (look up picture)Wanted to know what Earth looked like before organismsPut together what they thought was the original compounds in the air but forgot oxygenCreated lightningWould something living come out of this experiment? No, it didn’t workRan for a few days and realized the water they were circulating got brown which told them some kind of reaction was happeningTook a sample of water but still nothing living, but some of the molecules that were forming were biological molecules (building blocks of life)So if this process happened all over the Earth with millions of years we could possibly create somethingPurified water electric spark chamber stimulates a lightning storm gases of primeval atmosphere organic molecules appear after only a few daysTheory of evolution by natural selectionWhen life appeared through time it began to change for over 4 billion years100 billions of species on planet todayAll relatedPrebiotic soupHow did life begin?A few centuries ago:People thought that new living things appeared all of the timeDidn’t have much technology, no microscopesThrough seasons things tend to “appear” all the timeSpontaneous Generation RefutedMid 1800s Louis Pasteur (famous for pasteurizing milk)Broth in flask is boiled to kill preexisting microorganisms as broth cools, condensing water collects, sealing the mouth of the flask (no life in flask, it wouldn’t spoil) if neck is later broken off, outside air can carry microorganisms into brothLife came from the air (outside environment)Ex. If leave a steak on counter as opposed to putting in a sealed containerContradicts the spontaneousness that life just started somehow 4 billion years agoConditions on Early EarthAtmosphere:CO2, CH4, NH3, H2, N2, HCl, H2S, H2O (similar to Jupiter)No free oxygenFrequent storms with lots of lightning (massive sources of energy that help catalyze things on Earth)Frequent volcanic eruptions (massive sources of energy that help catalyze things on Earth)Frequent meteor impacts (massive sources of energy that help catalyze things on Earth)UV light from the sunNo ozone layerEarth before life AroseEarth is about 4.6 billion years oldRadiometric dating of meteorites and moon rocks (how we measures this)What can change rate of decay- speed of lightLife arose about 3.8 billion years agoChemical traces in rocks 3.8 billion years agoFossil bacteria in rocks 3.5 billion years agoNo spontaneous generation now, but must have happened thenFrom that life we have all life on planet todayRate of decay of 40K to 40ArPotassium 40 (40K) naturally decays to argon 40 (40 Ar)Half livesKnow this!Look at powerpointHow to Assemble a Living ThingAccumulation of organic moleculesPre-biotic soupCatalyze reactionsEnzymes (proteins) or peptide bonds (some RNAs)Reproduce from stored genetic information (DNA)Separate the living thing from the outside environmentMembranesThe Chicken of the Egg?Now: DNA RNA Protein (central dogma of biology)Need proteins to synthesize more DNAHow do you replicate DNA?DNA helicase, polymerase, okasaki fragment (DNA ligase)Three proteins to make DNATo make proteins you need DNARNA to store information and can catalyze certain reactionsSo how did earliest cells do it?Ribozymes (RNA enzymes): RNA molecules that can catalyze reactions, especially those involved in synthesis and processing of RNA itselfConclusion: Earliest cells used RNA to store informationRibozymes to catalyze reactionsSeparate inside from outsideMicrospheres as Proto-CellsJust add fat and protein to water then shakeDifferent amino acids: hydrophobic, hydrophilic, disulfide-bondsWater + elements + energyPrebiotic soupAmino acids, nucleotides, lipids, sugarsMicrospheres like protocels surrounding more complexOrganic molecules like- RNA, carbohydrates, proteins, lipidsFirst prokaryotes (science miracle)Drake equation of the probability of this ever happening anywhere else“Family Tree” of life (phylogeny/evolutionary tree)Look at pictureEucarya (third) (multicellular)Land plants, green algae, red algae, amoebas, cellular slime molds, animals, fungi, forams, ciliates, dinoflagellates, diatoms, euglena, trypanosomes, leishmaniaArchaea (second)Sulfolobus, thermophiles, halophiles, methanobacteriumBacteria (first)Green nonsulfur bacteria, mitochondrion, spirochetes, chlamydia, green sulfur bacteria, cyanobacteria, plastids including chloroplastsCommon ancestor of all life (first species)Because of this we have 100 million speciesRight off the bacteria branchHomo sapiens (200,000 years)Theory of evolution by natural selectionEvolved from very simple bacteriaBody composed of 50 trillion cellsPrinciples of EvolutionWhy are there so many species?Taxonomic family groups classification- LenaisPredicted evolution from certain thingsWhat is science, theory, hypothesis? Look in power pointCharles DarwinTheory of EvolutionPeople realized before him that there were family classifications and groups and had a hypothesis that life on the planet changedDidn’t know about DNA (Mendel)Wallace also had similar ideas so they communicated but were also competing (Darwin beat him to it)Voyage of HMS BeagleWent around South America, Africa, Great Britain, Galapagos Islands, and around AustraliaTook samples of fossilized creature and other living samplesAs the creatures moved from South America to the Galapagos Islands they started to changeThe tortoise shells were differentSwimming iguana for seaweedFinches (Darwin thought they were a bunch of different types of birds) modern day DNA has placed them all in the IslandsSeed eaters, bud eaters, insect eatersThe Origin of Species by means of natural selection was published in 1859At this time it was a hypothesisMain points of “Origin of Species”Evolution occurs in populationsPopulation- all individuals of one species in one areaGrowth with reproduction, inheritance, variability, a ratio of increase so high as to lead to a struggle for lifeWhales don’t have arms because it was
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