1. Water cycle Carbon cycle Nitrogen cycle
There are a number of cycles found in nature, continuously circulating nutrients and substances around biological systems.
Water cycle
Carbon cycle
Nitrogen cycle

2. Why do scientists care about Carbon?
Carbon is the main constituent of all living cells.
Living things need carbon to make most of the molecules in our body (fats, carbohydrates, nucleic acids (DNA) and proteins)

3. Carbon is abundant in the air…
…as carbon dioxide.

4. Which is great news for plants.
They can’t eat food, so they make their own sugar by photosynthesis.

5. Photosynthesis:
Plants take in water (H2O) from the soil through their roots.
And carbon dioxide (CO2) from the air in through their leaves.
Then they use sunlight energy to rearrange these into molecules of glucose (a sugar).

6. Some glucose is stored by the plant as starch (e. g
Some glucose is stored by the plant as starch (e.g. potatoes) or as cellulose in the plant cell walls.
Which is great news for consumers, as they can eat plants and use the energy in the food to move and build their bodies.
photosynthesis

7. They do this by respiration.
To move and grow, both plants and animals need to break down glucose to release that chemical energy.
They do this by respiration.
Respiration:
Plants and animals take in oxygen (O2) from the air.
They use the oxygen to break down glucose, producing carbon dioxide (CO2) and water (H2O) as waste.
feeding
photosynthesis

8. respiration
feeding
photosynthesis

9. Some day, this goat will die…
…which is great news for decomposers like bacteria and fungi.
They break down dead organisms and in doing so, release the carbon into the air as carbon dioxide (CO2).
The carbon which is locked up in the body of organisms is not lost forever.
respiration
feeding
photosynthesis

10. respiration
feeding
photosynthesis
decomposition

11. Millions of years ago, some decaying organisms were covered by layers of sand and rock.
The pressure caused them to fossilise and form fossil fuels.
respiration
feeding
photosynthesis
decomposition

12. respiration feeding photosynthesis decomposition
We can extract these fossil fuels from underground and burn them to release energy. This process is called combustion.
It releases carbon dioxide (CO2) into the atmosphere.
respiration
feeding
photosynthesis
decomposition

13. The Carbon Cycle combustion respiration feeding photosynthesis
decomposition