Carbon and water cycles

• How long has life on Earth existed?

  Billions of years
• Why has life on Earth been possible?

  Because it recycles molecules and atoms
• What happens to atoms over millions of years?

  They can be reused to create different organisms
• How many atoms are estimated to be in a human body?

  Six octillion atoms
• Where have the atoms in your body been recycled from?

  Oceans, volcanoes, other animals, and humans
• What are the two cycles covered in the study material?

  • Water cycle
  • Carbon cycle
• What is the first step in the water cycle?

  Energy from the sun causes evaporation
• What types of water can evaporate in the water cycle?

  Water from lakes, oceans, rivers, and land
• What is transpiration in the water cycle?

  Evaporation of water from plant leaves
• What happens to water vapor as it accumulates in the sky?

  It condenses into clouds
• What is the term for water falling back to Earth?

  Precipitation
• After precipitation, what can happen to the water?

  It can seep into soil, flow into rivers, or be taken up by plants
• What are the main stores of carbon in the carbon cycle?

  • Atmosphere (as carbon dioxide)
  • Plants (in biological molecules)
  • Soil (with microorganisms)
  • Fossil fuels (underground)
  • Animals (in biological molecules)
• What is the most important process in the carbon cycle?

  Photosynthesis
• What do plants and algae do during photosynthesis?

  They convert carbon dioxide into glucose
• What happens to carbon after plants are consumed by animals?

  It can be released back to the atmosphere by respiration
• What occurs when organisms die in aerobic conditions?

  Microorganisms decay them, releasing carbon dioxide
• What happens to organisms that die in anaerobic conditions?

  They may be converted into fossil fuels
• What can fossil fuels be burned to produce?

  Carbon dioxide
• What additional process can be included in the carbon cycle?

  Burning of plants or biofuels
• What are the key processes in the carbon cycle?

  1. Photosynthesis
  2. Respiration
  3. Decay by microorganisms
  4. Formation of fossil fuels
  5. Burning of fossil fuels