5Where does life come from? Spontaneous generationthe belief that living things arise from nonliving thingsBiogenesisall living things come from other living thingsRedi’s experimentsSpallanzani’s experimentsPasteur’s experiments
6Redi’s Experiment ( )Italian physician and poet who demonstrated that the presence of maggots on rotting meat does not result from spontaneous generation but from eggs laid on the meat by flies.Pg. 279
7Spallanzani’s Experiments (1729-1799) Italian naturalist whose experiments disproved that microorganisms spontaneously generated from meat broth in open flasks.Pg. 280
8Pasteur’s Experiment (1822-1895) A French chemist who proved that microorganisms are carried by dust and not air.Improved on Spallanzani’s experimentPg. 281
10The First Organic Compounds Alexander Oparin’s Hypothesis, 1920’s):Thought that primitive atmosphere contained: NH3, H2, H20, and C-H compoundsAt high temperatures, these gases might have formed simple organic compounds like amino acids
11Oparin’s Theory Con’tWhen the Earth cooled, the water vapor condensed into lakes and seas with the organic compounds withinWith the help of lightening and UV radiation, these organic compounds reacted with each other forming macromolecules essential to life.
12Can that REALLY happen?Yes! According to experiments performed by Miller and UreyProducts of experimental synthesis:Amino acidsATPDNA nucleotides
13Attempts to Create Life Miller ExperimentSpark ChamberInput ChamberCondenserWater Vapor Forms
14Life began in Hydrothermal Vents Extreme conditions: high heat, acid levels, pressure, gasesSun cannot reach the bottom of the oceanChemosynthesis- organisms making their own energy from the chemicals in their enviro. (similar to photosynthesis)Currently populated by Archae
15Vents cont.Scientists have also traced the DNA of all currently living organisms back to a common ancestor extremophile that would have been found in the hydrothermal vents.
16“It came from outer space!” Some scientists hypothesize that organic compounds may have come from meteoroids from space
17Earth’s Age More than 4 BILLION years old! How do scientists “know” this?Radiometric datingMeasurement of the decay of commonly occurring radioactive isotopesEx) Carbon dating
18Fossils The remains of ancient animals and plants Found in every continent on earthFormed from sedimentary rockPaleontology- the branch of biology that studies past forms of life (namely fossils!)
20The Fossil RecordFrom the 1830s onwards, geologists noted how fossils became more complex through time. The oldest rocks contained no fossils, then came simple sea creatures, then more complex ones like fishes, then came life on land, then reptiles, then mammals, and finally humans. Clearly, there was some kind of 'progress' going on.
21The First Prokaryotes About 3.5 bya the first prokaryotes, cells without a true nucleus (like bacteria), came into existence.The first cells were probably anaerobic and heterotrophic.Video
22Prokaryotes cont.Resemble modern day Archaebacteria, which live in extreme environmentsChemosynthesis- the conversion of carbon molecules (like CO2 or methane) into organic compounds without the use of sunlightenergy is obtained from aninorganic substance like sulfur,hydrogen gas, or methane
23Rise of photosynthesis and aerobic respiration Cyanobacteria- group of unicellular, autotrophic prokaryotes about 3 byaIncreased the level of atmospheric oxygen
24The First EukaryotesEndosymbiosis- about 2.0 bya, a small aerobic prokaryote began to live inside a larger anaerobic prokaryoteaerobic prokaryotes evolved to modern mitochondriaPhotosynthetic cyanobacteria evolved into chloroplastsvideo
26Ch. 14 Notebook Quiz What does the term biogenesis mean? Explain how Redi’s experiment disproved the hypothesis that flies formed by spontaneous generation.What is the Earth’s age? How do we know this?According to Oparin, what molecules were in Earth’s early atmosphere?What process increased the level of oxygen in the atmosphere about 3 bya?Explain the theory of endosymbiosis.