History of Life on Earth (in one powerpoint!)

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History of Life on Earth(in one powerpoint!)
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Earth's early history

• Earth is about 4.6 billion years old
• Very HOT
• Atmosphere did not contain oxygen
• Atmosphere contained gases toxic to life as we
  know it
• Hydrogen cyanide
• Carbon monoxide
• Hydrogen sulfide

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First organic molecules

• Thought to have formed from the hydrogen,
  methane, ammonia and water that were present
  sometimes called primordial soup
• Miller and Urey scientists who were able to
  produce amino acids in experiments simulating
  earths early conditions (1950s)

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The Puzzle of the first cells

• Under certain conditions, organic molecules form
  proteinoid microspheres which have some
  characteristics of cells (selectively permeable
  membranes, simple means of storing and releasing
  energy)

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Origin of genetic material

• How DNA evolved is still unknown
• One theory says that RNA evolved first (it can
  replicate on its own)
• Maybe RNA produced the first DNA and that led to
  the DNA-directed protein synthesis of cells today

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RNA and DNA
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Formation of an oxygen atmosphere

• First prokaryotic cells must have been able to
  survive without oxygen
• Prokaryotic cells evolved the ability to carry
  out photosynthesis, thus producing oxygen
• Other life forms that use oxygen could then
  evolve, other forms of life were driven extinct
  by the change in the atmosphere

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First eukaryotic cells

• Endosymbiont theory prokaryotic cells took up
  residence in other cells, the symbiotic
  relationship was beneficial (gave a selective
  advantage), led to eukaryotic cells that have
  membrane-bound organelles

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Evolution of Sexual Reproduction

• Evolved after eukaryotic cells came into
  existence
• Cells exchanged genetic material, leading to
  increased variation
• Of the many new combinations, some will produce
  favorable traits that will be selected through
  natural selection

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Evolution of Multicellularity

• Single cells could live together as a colony
• If this provided an advantage, it would be
  selected
• Led to multicellular organisms

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Mammal ancestors
Cynognathus, Triassic
Thrinaxodon, early Triassic
True mammals evolved in the Jurassic period,
which followed the Triassic
Megazostrodon, Late Triassic
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Vertebrate Evolution