1. Movement of Elements Plants take up elements in the form of
carbon dioxide and ions from the soil
These pass through living organisms along the food chain
Eventually the living organisms die, are decomposed by micro-organisms and the nutrients become available again.

2. Carbon Cycle
burning and combustion: wood, coal, peat, gas and petrol are used in these processes. They are the remains of plants and animals which lived millions of years ago.

3. Addition of CO2 to the atmospheric pool
Respiration
Combustion
Decomposition
Removal of CO2 from the atmospheric pool
photosynthesis

4. Carbon Cycle
Amount of CO2 in air varies according to the balance between respiration and photosynthesis
How will the amount of CO2 vary during the day and night?

5. Human Activities and Carbon Cycle
Increased levels of CO2 in the atmosphere may lead to the greenhouse effect.
Due to burning fossil fuels and burning and ploughing up the tropical rainforests.
Forests contain a lot of stored C in trunks of trees.
The easiest way to clear land is to burn it – large amounts of CO2 are released. The balance between respiration and photosynthesis is upset.

6. Nitrogen Cycle

8. ENERGY N N

10. DNA
RNA

11. Adding nitrates

12. nitrogen-fixing bacteria
Specialised groups of bacteria work in the cycle. These are:
decomposers
nitrifying bacteria
nitrogen-fixing bacteria
denitrifying bacteria

13. Nitrogen Cycle

14. decomposers
break down the nitrogen compounds in dead organisms (protein/DNA/RNA) and waste material (urea) releasing ammonium compounds (NH4+)

15. oxidise ammonium to nitrites and then nitrates (nitrification)
nitrifying bacteria
oxidise ammonium to nitrites and then nitrates (nitrification)

16. nitrogen-fixing bacteria
these live free in the soil or in root nodules of leguminous plants and synthesise organic
N-containing compounds such as
amino acids from nitrogen gas.
Nitrogen fixation only occurs in anaerobic conditions, in the root nodules.
(Also occurs in thunderstorms and Haber process)

17. root
nodules

18. denitrifying bacteria
in anaerobic conditions
(water-logged or compacted soils) nitrates are broken down releasing nitrogen gas back into the atmosphere (denitrification)

20. Humans and the N Cycle Robbing Nutrient Cycles
Growing crops and harvesting them removes nutrients from the soil.
Over years the losses are very great and eventually plants no longer grow
Can be replaced by adding natural or artificial fertilisers.