The Carbon Cycle

The Carbon Cycle
Poppy Matless

Carbon is present in all living organisms. When organisms die, the carbon is recycled for future generations.

1. Carbon is released as CO2 via respiration and combustion 2. CO2 is absorbed by producers (grass, plants etc) 3. Animals feed off of the plant, passing on carbon throughout the food chain, losing some carbon as CO2 respiration. 4. When the animal dies, it is eaten by decomposers, and the carbon returns to the atmosphere 5. If decomposition is blocked, the animal or plant material may become fossil fuel in the future for combustion.

Word and symbol equations

▪ Photosynthesis:
6H2O + 6CO2 + solar energy=C6H12O6 + 6O2
Water + Carbon dioxide + solar energy=Glucose + oxygen ▪ Cellular respiration
C6H12O6 + 6O2=6H20 + 6CO2 + solar energy
This is the same as the equation for photosynthesis, but reversed.

Step 1 Explanation

When animals respire, they release CO2 into the atmosphere. CO2 is also released by the burning of fossil fuels, or combustion. The CO2 remains in the atmosphere, where it absorbs heat from the sun, and contributes to the greenhouse effect. Eventually, the CO2 is absorbed by plants through photosynthesis.

Step 2 Explanation

Plants absorb the CO2 through photosynthesis, by absorbing it through the stomata on the leaves. Other factors that contribute to photosynthesis are light intensity, amount of water and temperature.

Step 3 Explanation

When a producer is consumed, it passes on the energy from the carbon to the animal that consumed it. From creature to creature, a certain amount of energy and carbon is lost to the environment, through respiration and waste. This continues throughout the food chain, where it final stops at the tertiary consumer, when all energy is lost.

Step 4 Explanation

When an animal dies, it is eaten by decomposers. Decomposers include fungi and bacteria. Factors that influence decomposition include temperature, moisture and available nutrients. When an animal is consumed, decomposers release CO2 back into the atmosphere. Decomposers are essential to the cycle because without them all carbon would eventually become trapped in animal carcasses and other forms of waste.

Step 5 Explanation

If a dead animal is not consumed, it may become fossilized. Fossilization is when layers of sediment build up over the dead animal, and force it deeper into the ground. Over millions of years, it is forced so deep that temperatures underground begin to rise, and turn the remains into fossil fuels (coal, oil and natural gas). Humans then drill or mine for the fuels, which is expensive and can disturb the environment, to use as fuel for cars, heating, electricity etc.

Carbon Sinks

Carbon Sinks are anything that absorbs more carbon than they release, and Carbon Sources are anything that release more than they absorb. In the carbon cycle, Carbon Sinks include plants and trees that use photosynthesis. Carbon Sinks also include the ocean, as plankton absorbs the CO2 that has dissolved in surrounding water. Carbon sinks don’t change the total amount of carbon in the atmosphere, because about the same amounts are released each year because of Carbon Sources.

Humans affect on the Carbon Cycle

Human behaviour affects the cycle because of the extraction of fossil fuels. Fossil fuels do not naturally burn, and the rate of burning of fossil fuels is high. This means that there is too much CO2 in the atmosphere and the rate of plants respiring is not enough, and therefore the plants cannot keep up. Also, Humans are deforesting millions of trees and plants, which means that plants that can help to remove the CO2 are in fact removed themselves, and therefore the gas remains in the atmosphere, where it contributes to the greenhouse effect.