There are a number of cycles found in nature,
continuously circulating nutrients and substances
around biological systems.
• Water cycle
• Carbon cycle
• Nitrogen cycle
Why do biologists 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)
Carbon is abundant in the air…
…as carbon dioxide.
Which is great news for plants.
They can’t eat food, so they make their own
sugar by photosynthesis.
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.
Some
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photosynthesis
Respiration:
To move and grow, both plants and animals need to
Plants
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taketoinrelease
oxygen (O
the air.
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break and
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dioxide (CO2) and water (H2O) as waste.
feeding
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respiration
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photosynthesis
Some day, this goat will die…
The carbon which is locked up in
is great
newslost
for
the body …which
of organisms
is not
decomposers
like bacteria and fungi.
forever.
They break down dead organisms
and in doing so, release the carbon
into the air as carbon dioxide (CO2).
respiration
feeding
photosynthesis
respiration
feeding
photosynthesis
decomposition
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
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
The Carbon Cycle
combustion
respiration
feeding
photosynthesis
decomposition
carbon cycle animation