4.3: Carbon cycling

Prior Learning and retrieval practice

Essential idea: Continued availability of carbon in ecosystems depends on carbon cycling.

If energy is continually entering and exiting ecosystems what about the raw building materials?

Exercise 1: Think-Pair-Share:

• What are the building blocks of cells, organelles and molecules? What is the basic unit of matter?

• Where do these units come from? How are they made?

• Is there an infinite or finite number of them available on the planet do you think? Why?

A1: Estimation of carbon fluxes due to processes in the carbon cycle.

Guidance:

• Carbon fluxes should be measured in gigatonnes.

Exercise 2: Answer these questions:

• What is flux?

• What materials tend to have fluxes?

• If carbon is normally a solid, how does it have a flux?

• What processes cause carbon to flux?

• What is the relative size in gigatonnes of these processes?

• Why is carbon flux measured in gigatonnes and why are they estimated and not measured directly? What does this do to the uncertainty in the measurements?

Exercise 3: 

• Describe the changes that you can see in the graph. 

• Explain the trends.

U1: Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds.

U2: In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogencarbonate ions.

U3: Carbon dioxide diffuses from the atmosphere or water into autotrophs.

U4: Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere.

U5: Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere or accumulates in the ground.

U6: Methane is oxidized to carbon dioxide and water in the atmosphere.

U7: Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils.

U8: Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in porous rocks.

U9: Carbon dioxide is produced by the combustion of biomass and fossilized organic matter.

U10: Animals such as reef-building corals and mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone.

Exercise 4: Convert each of these understandings into a little diagram

S1: Construct a diagram of the carbon cycle.

Exercise 5: Connect each of your pictures together with arrows labelled as the processes that move carbon from one area to another