The Evolution of the Atmosphere

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

  About 80% nitrogen and 20% oxygen
• What gases make up less than one percent of the Earth's atmosphere?

  Carbon dioxide, water vapor, and noble gases
• What role did volcanic activity play in the early atmosphere?

  It created a carbon dioxide-rich atmosphere
• What organisms helped reduce carbon dioxide levels in the atmosphere?

  Algae and green plants
• Why is the evolution of algae and plants significant?

  They increased oxygen levels through photosynthesis
• What is the time frame for the first billion years of Earth's history?

  4.6 billion years ago
• What happened as water vapor condensed in the early atmosphere?

  It formed oceans that dissolved carbon dioxide
• How did carbon dioxide from the atmosphere become sediments?

  It dissolved in oceans and formed carbon precipitates
• When did algae begin to appear in Earth's history?

  About 2.7 billion years ago
• What is the process of photosynthesis?

  It takes in carbon dioxide and produces oxygen
• What happens to algae and plants when they die?

  They become buried in sediment and form rock
• What types of substances are formed from buried organic material?

  Sedimentary rock, oil, and gas
• What is coal primarily made from?

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

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

  • Intense volcanic activity produced carbon dioxide
  • Water vapor condensed to form oceans
  • Algae and plants evolved, reducing CO2 and increasing O2
  • Sedimentary rocks and fossil fuels formed from organic material
• What is the current composition of the Earth's atmosphere?

  Mostly oxygen and nitrogen
• Why do we still consider the evolution of the atmosphere a theory?

  Because it is based on evidence over billions of years
• How did the evolution of photosynthesis impact life on Earth?

  It allowed more complex life forms to evolve
• What is the significance of sedimentary rock in relation to carbon?

  It traps carbon to prevent it from entering the atmosphere
• What is the relationship between photosynthesis and atmospheric gases?

  Photosynthesis decreases CO2 and increases O2
• What types of organisms contribute to the formation of fossil fuels?

  Plankton and dead plant material
• what does emission of volcanic activity produce

  increased nitrogen
• how was coal formed from the carbon dioxide

  carbon dioxide is used during photosynthesis in trees (which) die and are compressed over millions of years