Nutrient Cycles

Question 1

Describe the carbon cycle

Answer 1

• Carbon compounds in plants formed millions of years ago from dead vegetation to form fossil fuels - oil, coal, peat, gas
• Carbon compounds in plants are eaten by animals => respiration and decay releases carbon dioxide
• Burning fossil fuels emit co2
• Co2 is taken in plants for photosynthesis
  (pg230)

Question 2

Describe the water cycle

Answer 2

• Energy from sun powers the water cycle
• Evaporation from sea
• Condensation of water to form cloud containing water droplets
• Gets colder as air rises. More water condenses out => droplets get bigger and heavier and fall as precipitation
• Water vapour from plants and animals return to the sea

Question 3

Describe the nitrogen cycle

Answer 3

• Enormous amounts of energy from lightning can break nitrogen allowing it to combine with oxygen to form nitrogen oxides to form NO3 (nitrate ions)
• NO3 enters the soil and is absorbed by plants through roots. Uses this nitrogen to make proteins.
• Nitrogen gas can enter the root. Nitrogen-fixing bacteria (found in root nodules of leguminous plants) can turn nitrogen gas into nitrates. This process is nitrogen fixation
• Animals eat plants and digest => when excrete/die, nitrifying bacteria break down proteins in the dead organism releasing nitrates into soil
• Denitrification is when denitrifying bacteria in soil break down nitrates and release nitrogen gas into the air