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Early Earth and the Origin of Life. Phylogeny. Traces life backward to common ancestors. How did life get started?. Fossil Record. Earliest - 3.5 billion years old. Earth - 4.5 billion years old. Prokaryotes. Fossil Modern. Bacterial Mats. Point.
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Phylogeny • Traces life backward to common ancestors. • How did life get started?
Fossil Record • Earliest - 3.5 billion years old. • Earth - 4.5 billion years old.
Prokaryotes Fossil Modern
Point • Life on earth started relatively soon after the earth was formed.
Chemical Evolution • The evolution of life by abiogenesis.
Steps 1. Monomer Formation 2. Polymer Formation 3. Protobiont Formation 4. Origin of Heredity
Primitive Earth Conditions • Reducing atmosphere present. • Simple molecules • Ex: H2O vapor • CH4 methane • Hydrogen H2, • Ammonia NH3
Complex Molecule Formation • Requires energy sources: • UV radiation • Radioactivity • Heat • Lightning
Oparin and Haldane 1920s • Hypothesized steps of chemical evolution from primitive earth conditions.
Miller and Urey, 1953 • Tested Oparin and Haldane’s hypothesis. • Experiment - to duplicate primitive earth conditions in the lab.
Results • Organic monomers formed including Amino Acids.
Other Investigator's Results • All 20 Amino Acids • Sugars • Lipids • Nucleotides • ATP
Hypothesis • Early earth conditions could have formed monomers for life's origins.
Polymer Synthesis • Problem: • Monomers dilute in concentration. • No enzymes for bond formation.
Possible Answer 1. Clay 2. Iron Pyrite
Explanation • Lattice to hold molecules, increasing concentrations. • Metal ions present which can act as catalysts.
Protobionts • Aggregates of abiotically produced molecules. • Exhibit some properties of life. • Ex: Osmosis • Electrical Charge • Fission
Protobiont Formation • Proteinoids + H2O microspheres • Liposomes + H2O lipid membranes
Coacervates • Colloidal droplets of proteins, nucleic acids and sugars surround by a water shell. • Will form spontaneously from abiotically produced organic compounds.
Summary • Protobionts have membrane-like properties and are very similar to primitive cells. • Start for selection process that lead to cells?
Question ? • Where did the energy come from to run these early cells?
Answer • ATP. • Reduction of sulfur compounds. • Fermentation.
Genetic Information • DNA RNA Protein • Too complex for early life. • Other forms of genetic information?
RNA Hypothesis • RNA as early genetic information.
Rationale • RNA polymerizes easily. • RNA can replicate itself. • RNA can catalyze reactions including protein synthesis. • Ribozymes
Ribozymes • RNA catalysts found in modern cells. • e.g. ribosomes • Possible relic from early evolution?
Molecular Cooperation • Interaction between RNA and the proteins it made. • Proteins formed may serve as RNA replication enzymes.
Molecular Cooperation • Works best inside a membrane. • RNA benefits from the proteins it made.
Selection favored: • RNA/protein complexes inside membranes as they were the most likely to survive and reproduce.
DNA Developed later as the genetic information • Why? More stable than RNA
Alternate View Life developed in Volcanic Vents.
Volcanic Vents • Could easily supply the energy and chemical precursors for chemical evolution. • Most primitive life forms are the prokaryotes found in or near these vents.
New Idea • Life started in cold environments. • Interface between liquid and solid allows concentration of materials and formation of polyomeres. • Molecules last longer too.
Modern Earth • Oxidizing atmosphere. • Life present. • Prevents new abiotic formation of life.
Hypothesis • Life as a natural outcome of chemical evolution. • Life possible on many planets in the universe.
Kingdom • Highest Taxonomic category • Old system - 2 Kingdoms 1. Plant 2. Animal
5 Kingdom System • R.H. Whittaker - 1969 • System most widely used today.
Main Characteristics • Cell Type • Structure • Nutrition Mode
Monera • Ex: Bacteria, Cyanobacteria • Prokaryotic
Protista • Ex: Amoeba, Paramecium • Eukaryotic • Unicellular or Colonial • Heterotrophic
Fungi • Ex: Mushrooms, Molds • Eukaryotic • Unicellular or Multicellular • Heterotrophic - external digestion • Cell wall of chitin
Plantae • Ex: Flowers, Trees • Eukaryotic • Multicellular • Autotrophic • Cell wall of Cellulose/Silicon