The Carbon Cycle
All living things are made of carbon. Carbon is also a part of the ocean, air, and even
rocks. Because the Earth is a dynamic place, carbon does not stay still. It is on the
move!
In the atmosphere, carbon is attached to some oxygen in a gas called carbon dioxide.
Plants use carbon dioxide and sunlight to make their own food and grow. The carbon
becomes part of the plant. Plants that die and are buried may turn into fossil fuels
made of carbon like coal and oil over millions of years. When humans burn fossil fuels,
most of the carbon quickly enters the atmosphere as carbon dioxide.
Carbon dioxide is a greenhouse gas and traps heat in the atmosphere. Without it and
other greenhouse gases, Earth would be a frozen world.
CARBON RESERVOIR I: ROCKS
The biggest carbon reservoir on earth is in rocks, weighing in at some 66 billion metric
tons of carbon. In very rare instances (as in roughly .004%), carbon in rock is in the form
of coal, oil or natural gas. Most of the time it occurs as a chemical component of plain
old granite, sandstone or limestone.
CARBON RESERVOIR II: THE SEA
The next-biggest reservoir for carbon on Earth is the ocean. Scientists tend to split the
ocean into two ‘pools,’ like a two-layer cake. The top layer goes from the surface to 100
meters down. Wind sloshes the water around, allowing CO2 gas to exchange with the
atmosphere.
The bottom layer – or deep ocean – is bigger and less exposed to the atmosphere, and
is therefore a good long-term storage place for large quantities of carbon.
Carbon moves between the ocean and atmosphere by diffusion. When the level of
CO2 in the atmosphere increases, some of it dissolves into ocean water.
Answer Bank for Questions
CELLULAR RESPIRATION: Respiration by
animals and plants
EATING PLANTS
PHOTOSYNTHESIS
PHOTOSYNTHESIS
(6 CO2 + 6 H2O→C6H12O6 + 6 O2)
GROUND
PLANTS REMOVE CO2 FROM THE
ATMOSPHERE AND USE IT TO GROW
FOSSILIZED CARBON FROM ANCIENT
PLANTS AND ANIMALS
GLUCOSE, CARBOHYDRATES, LIPIDS,
PROTEINS, DNA
PHOTSYNTHESIS AND RESPIRATION SHOULD
BALANCE EACH OTHER OUT
CO2
CELLULAR
RESPRATION
FUELS
PHOTOSYNTHESIS &
MOVEMENT OF
WATER
PRIMARY
CONSUMERS
GLUCOSE &
CARBOHYDRATES
All the oxygen would
be used up and all air
breathing organisms
would die
PLANTS
ALGAE
SOME BACTERIA
CONSUMERS
CARBON
Name_________________________________________
Period_______________
Carbon Cycle Worksheet
1. What element is found in all living things on Earth?
CARBON
2. What is the food-producing process in plants?
PHOTOSYNTHESIS
3. Write the chemical equation for this process.
6 CO2 + 6 H2O→C6H12O6 + 6 O2
Carbon Dioxide + Water = Glucose + Oxygen
4. Why could you say that plants are a sink for carbon?
PLANTS REMOVE CO2 FROM THE ATMOSPHERE AND USE IT TO GROW
5. What would happen if all the plants on earth died?
ALL THE OXYGEN WOULD BE USED UP AND ALL AIR BREATHING
ORGANISMS WOULD DIE
6. Where does the carbon in fossil fuels come from?
FOSSILIZED CARBON FROM ANCIENT PLANTS AND ANIMALS
7. Name an organic molecule that carbon is found in.
GLUCOSE, CARBOHYDRATES, LIPIDS, PROTEINS, DNA
8. What molecule do trees get their carbon from?
CO2
9. Where do primary consumers get their carbon from?
10.
EATING PLANTS
What process adds carbon to the atmosphere?
CELLULAR RESPIRATION: Respiration by animals and plants
11.
What process removes carbon from the atmosphere? PHOTOSYNTHESIS
12.
How does oxygen get into the water? PHOTOSYNTHESIS & MOVEMENT
OF WATER
13.
What do producers produce? GLUCOSE & CARBOHYDRATES
14.
List 3 groups of producers? PLANTS
15.
What group eats producers? PRIMARY CONSUMERS
16.
ALGAE
SOME BACTERIA
How does carbon get back into the atmosphere from the food we eat?
CELLULAR RESPRATION
17.
Where do secondary consumers get their carbon from? PRIMARY
CONSUMERS
18.
Where does an animal’s or plant’s carbon go when it dies? GROUND
19.
Why should the amount of carbon in the atmosphere stay the same?
PHOTSYNTHESIS AND RESPIRATION SHOULD BALANCE EACH OTHER
OUT
20.
How is extra carbon getting into the atmosphere today? BURNING FOSSIL
FUELS