Evolution of the Atmosphere

• What is the composition of the Earth's atmosphere?

  About 80% nitrogen and 20% oxygen
• What role did volcanic activity play in the early atmosphere?

  It created a carbon dioxide rich atmosphere
• How did algae and plants affect atmospheric composition?

  They reduced CO2 and increased oxygen levels
• What is the status of the theory regarding atmospheric evolution?

  It is supported by evidence but remains a theory
• How long has the Earth been evolving?

  About 4.6 billion years
• What characterized the Earth's atmosphere in the first billion years?

  It was dry with intense volcanic activity
• What gases were produced by volcanic activity?

  Carbon dioxide, water vapor, and nitrogen
• What happened to the carbon dioxide as water vapor condensed?

  It dissolved in the oceans
• What did dissolved carbon dioxide form in the oceans?

  Carbon precipitates and sediments
• When did algae begin to appear in Earth's history?

  About 2.7 billion years ago
• What process allowed algae and plants to affect atmospheric CO2 and oxygen levels?

  Photosynthesis
• How did the evolution of algae and plants impact life on Earth?

  It allowed more complex life to evolve
• What happens to algae and plants when they die?

  They become buried in sediment
• What do sedimentary rocks and fossil fuels trap?

  Carbon from dead organisms
• What type of organisms mainly form crude oil and natural gas?

  Dead plankton
• What is coal made from?

  Thick deposits of dead plant material
• What is limestone primarily made of?

  Calcium carbonate from marine organisms
• What are the key stages in the evolution of Earth's atmosphere?

  1. Intense volcanic activity produced CO2 and other gases.
  2. Water vapor condensed to form oceans.
  3. Algae and plants evolved, reducing CO2 and increasing oxygen.
  4. Dead organisms formed sedimentary rock and fossil fuels.
• What is the current composition of the Earth's atmosphere?

  Mostly oxygen and nitrogen
• What is the significance of sedimentary rock and fossil fuels?

  They trap carbon and store energy
• What is the relationship between photosynthesis and atmospheric changes?

  Photosynthesis decreases CO2 and increases oxygen
• How did the evolution of photosynthetic organisms change the Earth?

  It transformed the atmosphere for complex life