carbon dioxide and oxygen

• What process increased the atmospheric concentration of oxygen?

  Photosynthesis
• What is photosynthesis?

  It converts carbon dioxide and water into glucose and oxygen
• What were the first photosynthetic organisms to evolve?

  Algae
• How long ago did algae evolve?

  Approximately 2.7 billion years ago
• What was the impact of photosynthesizing plants evolving over the next billion years?

  It led to an increasing rate of oxygen accumulation
• What threshold was reached that allowed complex life forms to evolve?

  A threshold concentration of oxygen
• What are the three factors that caused atmospheric carbon dioxide to decrease?

  Oceans, photosynthesis, marine animals
• How did the formation of oceans affect atmospheric carbon dioxide?

  It removed large amounts of carbon dioxide
• What happens to carbon dioxide once it is dissolved in the oceans?

  It reacts with seawater to give carbonate precipitates
• Why is carbon dioxide important in photosynthesis?

  It is one of the reactants in the equation
• What role did marine animals play in the carbon cycle?

  They removed carbonates to build shells and skeletons
• What are the main processes that contributed to the decrease in atmospheric carbon dioxide?

  • Formation of oceans
  • Photosynthesis by algae and plants
  • Evolution of marine animals using carbonates