Period 2, Witmer, History of Earth

  • (5 BYA) No Earth yet

    (5 BYA) No Earth yet
    Our solar system and earth was a swirling mass of gas, dust, and debris.
  • (4.6 BYA) Earth Grew Larger

    (4.6 BYA) Earth Grew Larger
    Earth grew larger as gravity pulled in more debris
  • (4 BYA) Earth is Formed

    (4 BYA) Earth is Formed
    Earth became formally formed. Period of recorded history began.
  • (4 BYA) First Cells

    (4 BYA) First Cells
    The first cells were anaerobic, heterotrophic prokaryotes
  • (3.5 BYA) Fossils

    (3.5 BYA) Fossils
    Fossils of stromatolites as old as 3.5 billion years old are known.
  • (3 BYA) Life Forms

    (3 BYA) Life Forms
    Some forms of life had become photosynthetic.
  • (2.2 BYA) Same Earth

    (2.2 BYA) Same Earth
    Earth appeared the same as it does today.
  • O2 Levels

    O2 Levels
    O2 levels reached today's levels
  • (1.5 BYA) Endosymbiosis

    (1.5 BYA) Endosymbiosis
    A type of small aerobic prokaryote was engulfedby and began to live and reproduce inside of a larger, anaerobic prokaryote. This theory is called endosymbiosis.
  • (1 BYA) Ozone (O3) formed

    (1 BYA) Ozone (O3) formed
    protected organisms from harmful UV rays so they could exist on land
  • (1600-1700) Redi's experiment

    (1600-1700) Redi's experiment
    Prooved that flies come only from eggs laid by other flies; disprooved spontaneous generation theory
  • (1600-1700) First microscope

    (1600-1700) First microscope
    Revealed the world is filled with tiny creatures
  • (1700-1800) Spallanzani's experiment

    (1700-1800) Spallanzani's experiment
    designed experiment to test the hypothesis of spontaneous generation of microorganisms
  • (1800-1900) Pasteur's Experiment

    (1800-1900) Pasteur's Experiment
    Set up experiment that settled issue of spontaneous generation and prooved it wrong.
  • (1900-present) Thomas Cech

    (1900-present) Thomas Cech
    early 1980's found that a type of RNA found in some unicellular eukaryotes is able to act as a chemical catalyst.
  • (1900-present) Lynn Margulis

    (1900-present) Lynn Margulis
    proposed that early prokaryotic cells may have developed a mutually beneficial relationship
  • (1900-present) Urey and Miller

    (1900-present) Urey and Miller
    Set up experiments that produced a variety of compounds, including amino acids.
  • (1900-present) Radioactive Dating

    (1900-present) Radioactive Dating
    method to establish age of materials
  • (1900-present) Oparin's hypothesis

    (1900-present) Oparin's hypothesis
    It is that organic compounds undergo reactions leading to more complex molecules- evenually leading to first life forms. Used in Urey & Miller's experiment
  • (1900-present) Fox

    (1900-present) Fox
    did extensive research on the physical structures that may have given rise to the first cells