Section 14.2 CS

Section 14.2 Cheet Sheet

• Spontaneous generation – The idea that living material comes from nonliving material.

  • Was disproved by Francesco Redi and Louis Pasteur

    • Redi did the meat/fly experiment

    • Pasteur did the broth experiment

• Biogenesis – Life comes from life

• Simple organic molecules must have been formed on early Earth for life to arise.

  • Water vapor, carbon dioxide, nitrogen, and methane and ammonia in the atmosphere may have joined together via energy from the sun, lightning, and Earth's heat to form organic molecules.

  • These molecules would “brew” in a “primordial soup” until simple life arose called protocells.

  • Stanley Miller and Harold Urey tested the hypothesis and created organic molecules.

• The first life might have been heterotrophs, eating organic molecules found in the oceans, and anaerobic, because there was not an abundant amount of oxygen in the atmosphere.

• After all the food had been devoured by these heterotrophs, autotrophs would be favored by natural selection and would have evolved, called archaebacteria. These autotrophs would be photosynthetic, producing oxygen.

• These autotrophs increased the concentration of oxygen in the Earth's atmosphere and allowed aerobically energy producing organisms to evolve.

  • Lightning also may have converted much of the oxygen in the atmosphere to ozone, forming a shield from the dangerous ultraviolet radiation from the sun, which enabled more complex organisms to evolve.

• Lynn Margulis proposed a theory for how eukaryotes may have evolved, called the endosymbiont theory.

  • Mitochondria evolved from energy making bacteria.