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, noble gases
• 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 current theory about the evolution of the atmosphere based on?

  Evidence from the past 4.6 billion years
• What was the state of the Earth during the first billion years?

  It was really dry with intense volcanic activity
• What gases were produced by volcanic activity in the early atmosphere?

  Carbon dioxide, water vapor, nitrogen, methane, ammonia
• What happened to carbon dioxide as water vapor condensed?

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

  About 2.7 billion years ago
• What process do algae and green plants use to produce oxygen?

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

  Allowed more complex life like animals to evolve
• What happens to algae and green plants when they die?

  They become buried in sediment and form rock
• What types of fossil fuels are formed from dead plankton?

  Crude oil and natural 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 were the major changes in the Earth's atmosphere over billions of years?

  • Intense volcanic activity produced CO2
  • Water vapor condensed to form oceans
  • Algae and plants evolved, reducing CO2
  • Increased oxygen levels allowed complex life to evolve
  • Sedimentary rock and fossil fuels formed from dead organisms
• What is the current composition of the Earth's atmosphere?

  Mostly nitrogen and oxygen
• Why is the theory of atmospheric evolution still considered a theory?

  Because it is based on historical evidence
• How did sedimentary rocks and fossil fuels contribute to the atmosphere?

  They trapped carbon and prevented its return
• What is the significance of the first billion years of Earth's history?

  It was marked by volcanic activity and CO2 production
• What is the relationship between photosynthesis and atmospheric gases?

  Photosynthesis decreases CO2 and increases O2
• How did the evolution of photosynthetic organisms change the Earth's atmosphere?

  It shifted the balance towards more oxygen