Question

key question: how does the cycling of carbon through the abiotic and biotic components of ecosystems make carbon continually available to organisms?
carbon is an essential element of life and is incorporated into the organic molecules that make up living organisms. large quantities of carbon are stored in sinks, which include the atmosphere as carbon - dioxide gas (co₂), the ocean as carbonates and bicarbonates, and rocks such as coal and limestone. carbon cycles between the biotic and abiotic environment. carbon dioxide is converted by autotrophs into carbohydrates via photosynthesis and returned to the atmosphere as co₂ through respiration (fluxes). these fluxes can be measured. some of the sinks and processes involved in the carbon cycle, together with the carbon fluxes, are shown below. humans intervene in the carbon cycle through activities such as combustion and deforestation.

1. add arrows and labels to the diagram above to show:

(a) dissolving of limestone by acid rain
(b) release of carbon from the marine food chain
(c) mining and burning of coal
(d) burning of plant material

1. (a) name the processes that release carbon into the atmosphere:

(b) in what form is the carbon released?

1. name the four geological reservoirs (sinks), in the diagram above, that can act as a source of carbon:

(a)
(b)
(c)
(d)

1. (a) identify the process carried out by algae at point a:

(b) identify the process carried out by decomposers at b:

1. what would be the effect on carbon cycling if there were no decomposers present in an ecosystem?

Explanation:

Step1: Analyze carbon - releasing processes

Respiration by organisms, combustion of fossil fuels (like coal) and plant material, and decomposition are major processes that release carbon into the atmosphere.

Step2: Determine form of released carbon

Carbon is mainly released as carbon - dioxide ($CO_2$) gas during respiration, combustion and decomposition.

Step3: Identify geological carbon sinks

The four geological reservoirs (sinks) in the diagram are coal (and all fossil fuels), oil and gas, limestone, and soil.

Step4: Identify processes by organisms

Algae at point A carry out photosynthesis, which takes in carbon - dioxide from the environment to produce organic compounds. Decomposers at B carry out decomposition, breaking down dead organic matter and releasing carbon back into the soil and atmosphere.

Step5: Analyze impact of no decomposers

If there were no decomposers, dead plant and animal tissues would not be broken down. Carbon would remain locked in these tissues instead of being recycled back into the soil and atmosphere, disrupting the carbon cycle.

1.

• (a) Add an arrow from limestone to the atmosphere labeled "Dissolving of limestone by acid rain releases $CO_2$"
• (b) Add an arrow from the marine food - chain area to the atmosphere labeled "Release of carbon from the marine food chain"
• (c) Add an arrow from coal to the atmosphere labeled "Mining and burning of coal releases $CO_2$"
• (d) Add an arrow from plant material (in the "Carbon in plant and animal tissues" area) to the atmosphere labeled "Burning of plant material releases $CO_2$"

2.

• (a) Respiration, combustion (of fossil fuels and plant material), decomposition.
• (b) Carbon - dioxide ($CO_2$).

3.

• (a) Coal (and all fossil fuels)
• (b) Oil and gas
• (c) Limestone
• (d) Soil

4.

• (a) Photosynthesis
• (b) Decomposition

1. Dead plant and animal tissues would not decompose, carbon would be locked in them, disrupting the carbon cycle.

Answer:

1. See above for arrow and label additions.
2. (a) Respiration, combustion, decomposition. (b) Carbon - dioxide ($CO_2$).
3. (a) Coal (and all fossil fuels) (b) Oil and gas (c) Limestone (d) Soil
4. (a) Photosynthesis (b) Decomposition
5. Dead plant and animal tissues would not decompose, carbon would be locked in them, disrupting the carbon cycle.