C9

• What was the early atmosphere likely composed of?

  Mainly carbon dioxide and virtually no oxygen
• Why is it hard to prove theories about the early atmosphere?

  Gathering evidence from 4.6 billion years ago is difficult
• What caused a decrease in atmospheric CO₂?

  Absorption of carbon dioxide to form oceans
• What do shells and skeletons contain from oceans?

  Carbonates
• How did carbon become locked up in rocks and fossil fuels?

  Through compression of dead organisms by sediment
• What are the main fossil fuels mentioned?

  Coal, crude oil, and natural gas
• When did algae evolve?

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

  Photosynthesis
• What was the impact of increased atmospheric oxygen?

  It led to the evolution of animals
• What gases are considered greenhouse gases?

  Carbon dioxide, methane, and water vapour
• What is the greenhouse effect?

  Absorption and re-radiation of long wavelength radiation
• How do human activities contribute to increased CO₂ levels?

  Deforestation and burning fossil fuels
• What are some consequences of climate change?

  Flooding, severe storms, and food production issues
• What is a carbon footprint?

  Amount of greenhouse gases released over a life cycle
• How can carbon footprints be reduced?

  By reducing carbon dioxide and methane emissions
• What pollutants are released from fossil fuel combustion?

  Gases and particles that pollute the air
• What is a major effect of carbon monoxide?

  Stops blood from transporting enough oxygen
• What causes acid rain?

  Oxidation of sulfur impurities during combustion
• How does nitrogen oxide form?

  From the reaction between nitrogen and oxygen in heat
• What are the effects of air pollution on health?

  Respiratory problems and global dimming
• What is global dimming?

  Reduction in sunlight reaching the Earth's surface