8.2.2

8.2.2 Plants in the Carbon Cycle

Have your Science
Notebook handy page 76

Recall: The carbon cycle moves carbon atoms between living and nonliving parts of the ecosystem.

As chemical reactions rearrange atoms, carbon can take many forms including:

• carbon dioxide

• glucose

• calcium carbonate

• fossil fuels

​Think about this image. What do you notice?

Labelling

Label the what is in of each carbon reservoir.

Drag labels to their correct position on the image

protein

fossil fuels

carbon dioxide

glucose

Remember, carbon reservoirs, or sinks, are places where carbon is stored for a long or short period of time.

Carbon reservoirs can hold large volumes of carbon atoms before they move to the next part of the carbon cycle.

Plants are an important carbon reservoir and also contribute to fossil fuels (another carbon reservoir).

Carbon Reservoirs

Multiple Choice

Which carbon reservoir holds most of its carbon in the form of carbon dioxide, CO₂ ?

• fossil fuels

• organisms

• rocks

• atomsophere

Common plant carbon reservoirs:

1. Trees: During photosynthesis, they use carbon dioxide from the atmosphere to produce glucose.
   
   Trees convert a lot of the glucose into molecules that form the trunk.
   
   Once carbon is stored in a tree's trunk, it stays there for the tree's entire life.

​Redwoods can store tons of carbon in their trunks for centuries.

2. Farm Crops: The plants convert carbon dioxide from the atmosphere into glucose.

   When crops are harvested, some of that glucose is in the parts of the plant used for food.
   
   When you eat fruit or vegetables, you use the glucose in that food for energy.

​Most crop plants store carbon for a few months before the crops are harvested.

3. Phytoplankton are microscopic, plant-like organisms—usually protists or algae—that live in water and perform photosynthesis. Though not technically plants, they act as producers in aquatic ecosystems.

   They mostly live near the surface of lakes, rivers, and oceans, using dissolved carbon dioxide for photosynthesis. Many aquatic animals rely on them for food.

Long chains of hydrocarbons form from the remains of plant matter.

Hydrocarbons burn easily, so we use them for fuel.

For example: Propane for stoves and grills.

During combustion, the bonds between that atoms are broken, releasing energy.

Burning a fossil fuel does two things:

1. Releases a lot of energy quickly, making them excellent sources of energy.

2. Release carbon dioxide into the atmosphere.

​The carbon that you release when you burn a fossil fuel was held in an underground reservoir for millions of years.

Using fossil fuels for energy releases millions of years of stored carbon very quickly.

Plants and other producers play a key role in the carbon cycle by absorbing carbon dioxide from the atmosphere during photosynthesis. This helps regulate the greenhouse effect, which is necessary to maintain Earth’s temperature.

Plants help keep carbon levels in the atmosphere in balance.

Fossil fuel formation:

A fossil fuel is an energy source that is formed from the remains of dead organisms. The three most common types of fossil fuels are:

• coal

• oil (petroleum)

• natural gas

Humans use fossil fuels as sources of energy to power homes, businesses, automobiles, etc.

​Plant matter falls in or is covered by flooding. Soil and organic matter bury it.

​Over time, sediment builds creating pressure.

​After millions of years of pressure and high temperatures, the plant matter becomes fossil fuels (coal, natural gas, and petroleum).

​Animal remains also turn into fossil fuels, but most carbon in fossil fuels comes from plants.

Reorder

Drag to correctly order the steps of fossil fuels formation.

• Plant matter is covered with water.

• Layers of sediment cover the plants.

• Sediment cause pressure, high temperatures occur.

• Plant matter becomes a fossil fuel.

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

​Great work today!

Tomorrow: Live Classroom Fun

Friday: Assignment-Reservoirs in the Carbon Cycle