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Evolution V: Macroevolution


Macroevolution & the Origin of Life AP Biology Macroevolution Macroevolution describes patterns of evolution for groups of species over extended periods of geologic ... – PowerPoint PPT presentation

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Title: Evolution V: Macroevolution

Evolution V Macroevolution the Origin of Life
  • AP Biology

  • Macroevolution describes patterns of evolution
    for groups of species over extended periods of
    geologic time
  • There are two distinct theories
  • Phyletic Gradualism
  • Punctuated Equilibrium

gradual evolution and speciation
rapid evolution and speciation
Phyletic Gradualism
Punctuated Equilibrium
Phyletic Gradualism
  • This theory argues that evolution occurs by the
    gradual accumulation of small changes.
  • Individual speciation events or major changes
    occur over long periods of time.
  • Fossil evidence provides snapshots of the
    evolutionary process, but that is considered a
    testament to the incompleteness of the available
    fossil record

Punctuated Equilibrium
  • This theory argues that evolutionary history
    consists of geologically long periods of stasis
    with little or no evolution, interrupted, or
    punctuated by geologically short periods of
    rapid evolution
  • This theory attempts to explain why few fossils
    of intermediate stages are found, since they only
    occur in short bursts of evolutionary time

The Origin of Life
  • The study of how life began is called Chemical
  • Heterotroph Theory proposes that the first cells
    were heterotrophs (couldnt make their own food)
  • The theory of the origin of live can be outlined
    in the following 9 steps

Origin of Life
  • 1. The earth and its atmosphere are formed
  • The primordial atmosphere originated from
    outgassing of the molten interior of the planet
    (through volcanos) and consisted of CO, CO2, H2,
    N2, H2O, S, HCl and HCN, but little or no O2

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Origin of Life
  • 2. The primordial seas formed
  • As the earth cooled, gases condensed to produce
    primordial seas consisting of water and minerals

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Origin of Life
  • 3. Complex Molecules Synthesized
  • Energy catalyzed the formation of organic
    molecules from inorganic molecules
  • Organic soup formed
  • Complex molecules included acetic acid,
    formaldehyde, and amino acids
  • These molecules are monomers that would become
    the building blocks for the synthesis of polymers

3 Evidence
  • A.I. Oparin and J.B.S. Haldane independently
    theorized that simple molecules could only form
    in the absence of the highly reactive oxygen
  • Stanley Miller tested the theories of Oparin and
    Haldane by simulating an experiment under
    primordial conditions. He applied electric sparks
    to simple gases (not oxygen) connected to a flask
    of heated water. After 1 week, the water
    contained various organic molecules including
    amino acids.

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Origin of Life
  • 4. Polymers and self-replicating molecules were
  • Monomers combined to form polymers. Some made by
    dehydration condensation (removal of water)
  • Protenoids are abiotically produced polypeptides.
    They can be experimentally produced by allowing
    amino acids to dehydrate on hot dry substances

Origin of Life
  • 5. Organic molecules were concentrated and
    isolated into protobionts
  • Protobionts were the precursors of cells. They
    could carry out chemical reactions enclosed
    within a border across which materials can be
    exchanged, but couldnt reproduce
  • Microspheres and coacervates are experimentally
    (and abiotically) produced protobionts that have
    some selectively permeable qualities

Origin of Life
  • 6. Primitive Heterotrophic Prokaryotes Formed
  • Heterotrophs are living organisms that obtain
    energy by consuming organic substances (i.e.
    pathenogenic bacteria)
  • The organic soup was a source of organic
    material for the heterotrophic cells to consume
    for energy
  • As the cells reproduced, competition drove
    natural selection to favor those cells most
    successful at obtaining food

Origin of Life
  • 7. Primitive Autotrophic Prokaryotes were Formed
  • As a result of mutation, a heterotroph gained the
    ability to produce its own food. As an autotroph,
    it had a successful advantage
  • Autotrophs make their own organic compounds using
    light energy or the energy of inorganic
    substances (i.e. cyanobacteria)

Origin of Life
  • 8. Oxygen and the Ozone Layer Formed and Abiotic
    Chemical Evolution Ended
  • As a by-product of the photosynthetic activity of
    the autotrophs, oxygen is released and
    accumulates in the atmosphere
  • Ozone layer formed when O2 interacts with UV
  • Ozone layer blocks UV light and ends a major
    source of energy for the abiotic synthesis of
    organic molecules

Origin of Life
  • Eukaryotes Formed (endosymbiotic theory)
  • Endosymbiotic Theory states that eukaryotic cells
    originated from a mutually beneficial association
    (symbiosis) among various kinds of prokaryotes
  • Mitochondria, chloroplasts, and other organelles
    established residence inside another prokaryote,
    producing a eukaryote

9 Evidence
  • A) Mitochondria and chloroplasts possess their
    own DNA (circular and naked)
  • B) Ribosomes of mitochondria and chloroplasts
    resemble those of bacteria
  • C) Mitochondria and chloroplasts reproduce
    independently of their eukaryotic host cell
    (binary fission)
  • D) Thylakoid membranes of chloroplasts resemble
    the photosynthetic membranes of cyanobacteria
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