Evolutionary Biology Chapter 6

Evolutionary Biology

• Evolutionary Biology examines changes in living organisms on Earth over time.
• Understanding the origin of life requires context on the universe's beginnings.

Origin of Life

• Observing stars allows us to look back in time; stellar distances are measured in light years.
• The universe is vast, containing objects whose light has traveled millions of years to reach us.
• The Earth is about 4.5 billion years old and part of the Milky Way galaxy.
• Early Earth had a dense atmosphere composed of water vapor, methane, carbon dioxide, and ammonia.
• As the Earth cooled, water vapor condensed to form oceans.

Theories on the Origin of Life

• Origin in Outer Space:

  • Suggests life on Earth may have been transferred from other planets around 4 billion years ago.

• Theory of Spontaneous Generation:

  • Early belief held that life arose from decaying matter.
  • Louis Pasteur disproved this, demonstrating that new life only comes from existing life, not spontaneously from non-living substances.

• Theory of Chemical Evolution:

  • Proposed by scientists like Oparin and Haldane, this theory suggests life started from non-living organic molecules.
  • Early Earth conditions included high temperatures, volcanic activity, and a reducing atmosphere containing methane (CH4) and ammonia (NH3).
  • In 1953, S.L. Miller simulated these conditions, leading to the formation of amino acids, sugars, and organic molecules in his experiments, supporting the idea of chemical evolution.