Early Earth and the Origin of Life - PowerPoint by aR0YH3YN

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									  Chapter 26
Early Earth and the
   Origin of Life
          Phylogeny

Traceslife 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
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, CH4, H2, 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
All20 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
Protobionts
     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.
Rs and Ps developed much
 later.
     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
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
CellType
Structure
Nutrition Mode
           Monera
Ex: Bacteria, Cyanobacteria
Prokaryotic
          Protista
Ex: Amoeba, Paramecium
Eukaryotic
Unicellular or Colonial
Heterotrophic
Review Chapter 28
              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
            Animalia
Ex: Animals, Humans
Eukaryotic
Multicellular
Hetrotrophic - internal
 digestion
No cell wall
        Other Systems
Multiple Kingdoms – split life
 into as many as 8 kingdoms.
 (review Chapter 28)
Domains – a system of
 classification that is higher
 than kingdom.
      3 Domain System
Based  on molecular structure
 for evolutionary relationships.
Prokaryotes are not all alike
 and should be recognized as
 two groups.
Gaining wider acceptance.
          3 Domains
1. Bacteria – prokaryotic.
2. Archaea – prokaryotic, but
 biochemically similar to
 eukaryotic cells.
3. Eucarya – the traditional
 eukaryotic cells.
            Summary
Systematics    is still evaluating
 the evolutionary relationships
 of life on earth.
Be familiar with the
 conditions of primitive earth.
Know the steps of chemical
 evolution.
         Summary
Recognizethe 5 Kingdoms.
Know about Domains.

								
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