THE CARBON CYCLE CHAPTER 2.5 Carbon Cycle
THE CARBON CYCLE Carbon is an element. Carbon atoms are the basis for all living things (called organic matter) and for all matter that was once living (called detritus). Carbon is stored in FOUR places: Living things The atmosphere The ocean The earth’s crust
These storage places are called carbon sinks. Carbon is removed from the atmosphere by plants when they photosynthesize to make sugar. Reactants Products 6CO2 + 6H2O + light = C6H12O6 +6O2 carbon dioxide + water + light = sugar (glucose) + oxygen
Carbon is returned to the atmosphere by plants and by animals when they respire or exhale. Reactants Products C6H12O6 + O2 = CO2 + H2O sugar + oxygen = carbon dioxide + water
Photosynthesis and cellular respiration are complementary processes, and because the carbon that they use is repeatedly cycled through both processes, this relationship is often called the CARBON CYCLE.
Most of the carbon that forms living organisms is released to the atmosphere or water as carbon dioxide as dead organisms decay. Under certain conditions, the decay process is delayed, and the organic matter may be converted into rock or fossil fuels such as coal, petroleum and natural gas.
This carbon is not released until the combustion process takes place through burning the fuels.
Reservoirs for Inorganic Carbon Carbon, when not in organic form, can be found in three main reservoirs (storage areas): The atmosphere The oceans The Earth’s crust
The Ocean Carbon is also found in seashells (both large and microscopic). When these fall to the bottom of the oceans and get covered with sediment over millions of years they will form limestone.
(Millions of tonnes of soil) Shells and Bones Sink to the bottom of the ocean Covered by sediment (Millions of years) Form limestone
Reservoirs for Organic Carbon Organic carbon is also held in reservoirs – the bodies of living things. All living things die and decomposition eventually returns the carbon to the cycle in inorganic form.
Q/A What is the human impact on the Carbon Cycle? Humans are increasing CO2 in the atmosphere by clearing away vegetation (forests) and by burning fossil fuels.
One Important Exception Bogs – store huge quantities of carbon in organic form Bogs have very little oxygen, therefore decomposition is very slow Carbon atoms may remain locked away in dead plant matter (peat) for many years in a bog. When plants decompose in a bog, they form peat that can get trapped under sediments over millions of years and form coal (another form of fossil fuel).
Die and decompose in a bog to form peat PLANTS Die and decompose in a bog to form peat Millions of years and tonnes of pressure form coal
Classwork Use your text, read pg 62-65 and answer the following questions: 1- 7 Work quietly at your desk. You may listen to your ipod/ mp3 while working. If I hear the music, you lose this privilege. When you are done these questions- Start reading about the Nitrogen Cycle on Pages 66- 67
Review for Test Things to know: The written and chemical forms of photosynthesis and cellular respiration. In photosynthesis, where in the cell is the change taking place? In cellular respiration, where in the cell is the change taking place? The completed table on pg. 84 Where our Carbon Sinks are. Where our Carbon Reservoirs are for inorganic and organic Carbon.
Response to Planet Earth: On the quiz you will be expected to respond to the movie we watched, “Planet Earth:Caves”. Things to think about: Types of Ecosystems we saw Different animals we were shown. Food webs that we were shown Some of these ecosystems did not have a plant life/ direct sunlight basis. Any other remarks or comments
CLASSWORK CARBON CYCLE HANDOUT You can listen to your ipod/ mp3 players while completing the handout. MAKE SURE THEY ARE ON LOW!