Unit 1 Photosynthesis and
carbon cycle
1.3 THE CARBON CYCLE
OBJECTIVES :
-find out how carbon
atoms move between
the air ,living
organisms and fossil
fuel.
- Bring together what
you know about
respiration and
photosynthesis .
CARBON AND LIVING THINGS :
• Carbon is an element that takes the solid form of either
graphite or diamond. Carbon is one of the basic elements of
any living thing.
• When animals eat food, they get carbon in the form of
carbohydrates and proteins.
• Decomposers break down carbon compounds and release
carbon back into the atmosphere as carbon dioxide where it
can be used by plants and other photosynthetic organisms.
Returning carbon
dioxide to the air :
- Respiration (
human –
animals-plants )
- Decomposers
respiration .
Fossil fuel and
combustion:
After millions of years
underground, the
compounds that make
up organisms turn into
fossil fuels.
Fossil fuel combustion is
the process of burning
coal, oil, natural gases, or
other fossil fuels to
create energy.
Carbon cycle :
the process in
which carbon
atoms continually
travel from the
atmosphere to the
Earth and then
back into the
atmosphere
Carbon cycle :
1/ photosynthesis
2/ respiration
3/feeding
4/formation of
fossil fuels
5/ decomposition
6/combustion
Past paper questions :
• This question is about the carbon cycle.
• (a) Name one process in the carbon cycle that releases carbon dioxide into
the atmosphere.
• (b) Which process in the carbon cycle uses microorganisms to break down
carbon compounds in dead plants and animals?
• (c) Which process in the carbon cycle moves carbon compounds along a
food chain?
• (d) Which process in the carbon cycle makes glucose?
• a/ respiration or combustion or decomposition (burning or decay or
rotting or decompose)
• (b) decomposition (decay or decompose)
• (c) feeding (eating or consumption or nutrition)
• (d) photosynthesis
