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The Origin of Life The development of life on Earth remains a puzzle

The Origin of Life The development of life on Earth remains a puzzle. Earth was very different billions of years ago. There have been many hypotheses of Earth’s origins. 1. The most widely accepted hypothesis is the nebula hypothesis .

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The Origin of Life The development of life on Earth remains a puzzle

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  1. The Origin of Life The development of life on Earth remains a puzzle

  2. Earth was very different billions of years ago There have been many hypotheses of Earth’s origins. 1. The most widely accepted hypothesis is the nebula hypothesis. • The solar system formed by a condensing nebula (a cloud of gas and dust in space)

  3. Ancient Earth • Atmosphere contents: • Ammonia, H2O vapor, Methane, H2, CO2 • Climate: • Extreme heat due to meteor impacts & volcanic activity • Eventually Cooling: Water vapor condensed (oceans formed) Click on picture to play video clip

  4. electrodes “atmosphere” water “ocean” heat source amino acids Several hypotheses propose how life began on Earth There are two organic molecule hypotheses: • 1. Miller-Urey Experiment • Energy from lightning created organic materials from inorganic ingredients • Result: amino acids and later nucleotides • 2. Meteorite Hypothesis • Amino acids may have arrived on Earth through meteorite or asteroid impacts (outer space). • 90 amino acids were found from this meteorite, only 19 of them can be found on Earth.

  5. There are different hypotheses of early cell structure • 1. Iron-sulfide Bubbles Hypothesis: • Compartments of chimney like structures on the ocean floor. • The compartments acted as the first cell membranes. • 2. Lipid Membrane Hypothesis • Lipid spheres, or liposomes, could form around a variety of organic molecules, acting as early cell membranes.

  6. Ribozymes are RNA molecules that catalyze their own replication. • DNA needs enzymes to replicate itself. RNA as Early Genetic Material A hypothesis proposes that RNA was the first genetic material

  7. Eukaryotic cells may have evolved through endosymbiosis • Endosymbiosis is a relationship in which one organism lives within the body of another. • Mitochondria and chloroplasts may have developed through endosymbiosis.

  8. The evolution of sexual reproduction led to increased diversity • Genetic variation is an advantage of sexual reproduction. • Sexual reproduction may have led to the evolution of multicellular life.

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