GEO 102 Lecture 24 Outline of Last Lecture I The Beginning of the Earth Outline of Current Lecture II What is Life III What are Living Things made of IV Experiments V Proteins Current Lecture What is Life How do we know something is alive o How is a rock different from a tree o Reproduction o Metabolism a sequence of chemical reactions What is a Virus o Not alive o It has DNA o It reproduces o But it can t reproduce by itself It has to hijack a cell in some other body o It doesn t metabolize by itself either o Outside another body it simply exists o Viruses evolve Between life and not life Viruses are in a grey area They DO NOT represent the first proto life Microspheres might better resemble the first life o They are organic carbon based but arise by themselves o They grow and divide like cells but more randomly What are living things made of These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Amino acids life s building blocks o You may have heard of them from your food o Can originate from non living things How did they originally form o Miller Urey experiment o Chemosynthesis o Geobiology Did life come from rocks or clay or undersea volcanoes Many think so How do they make amino acids You need o Carbon nitrogen hydrogen and oxygen o These are in the early atmosphere CO2 H2O N2 CH4 and NH4 o An external energy source is needed to start the reaction o Lightning o Chemical energy Experiments Miller Urey showed it could be done but used the wrong atmosphere More recent work has done this in a wide variety of circumstances Several possible cradles of early life have been identified This is but the first step though Proteins Amino acids are part of proteins Our bodies synthesize proteins How did they begin o Simple proteinoids have been formed in the lab o Experiments suggest that it may not have happened in water after all Group of protenoids cluster and form cell like structures protected by membranes Is this how it happened There is still a lot to be learned and it is developing story RNA and DNA o Reproduction o Space The geological record s earliest evidence of life is in indirect o Stable carbon isotopes at 3 8 bya The first undisputed fossils show up about 3 5 bya o Prokaryotic o Anoxic can not live without oxygen What did these organisms eat The earliest life is derived energy from breaking down components in their environment o Would not have lasted long Later life would ferment materials o Molecules such as sugars are split releasing carbon dioxide alcohol and energy About 3 5 bya photosynthesis began to be widespread Take home tip how oxygen became popular One way didn t require life Phot and chemosynthesis Life is from building blocks that can self assemble Still looking for how to tell if things are life life in extreme environments and making synthetic life
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