Ecosystems: The Carbon Cycle | A-level Biology | OCR, AQA, Edexcel

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The key points covered in this video include:

1. Introduction to Nutrient Cycles
2. The Carbon Cycle
3. The Human Impact on the Carbon Cycle
4. Maintaining the Balance of CO2 in the Air

Introduction to Nutrient Cycles

We have a finite supply of nutrients (atoms) on Earth. Therefore, ecosystems and habitats do not have an infinite number of nutrients (atoms) they can use. In order to keep habitats functioning, resources (atoms) must be recycled i.e. organic components broken down and rebuilt to be reused.

The Carbon Cycle

Carbon is a very important element - it is in carbohydrates, proteins and lipids. However, there is only a finite supply of carbon on the planet and so it must be recycled in nature through the Carbon Cycle. Animals respire to release carbon dioxide into the air. Plants and photosynthesising organisms take up this carbon dioxide and use it in photosynthesis - this aids in increasing plant biomass. Plants can be eaten by animals, and the carbon trapped in their biomass is transferred to these animals. These animals form a food chain and all die and are decomposed by detritovores, which also respire to release carbon dioxide into the air. If not eaten by animals, plants die and either decompose or fossilise (animals may also do the same) into fossil fuels, which when used by combustion engines release CO2 into the air. CO2 can also chemically react with water in the air to form carbonic acid and form acid rain, which erodes limestone statues to release more CO2 into the air.

The Human Impact on the Carbon Cycle

Before human interference, carbon dioxide levels in the air would fluctuate according to natural cycles. However, human activity is affecting the balance of CO2 in the atmosphere. For example, combustion engines are using up a lot of fossil fuels, which releases an increased emission of CO2 into the air. Deforestation for raw materials like timber mean there are less plants to trap CO2 from the air into plant biomass, thereby increasing levels of CO2 in the air. 1. We can use sustainable resources such as carbon neutral biofuels i.e. carbon trapped in photosynthesis is equal to carbon released by combustion. 2. Reforestation and planting on previously destroyed plant land increases number of carbon dioxide trapping organisms. The use of such procedures could help lower and restore the levels of carbond dioxide in the atmosphere.

Summary

There are not infinite resources on Earth - resources are finite
Therefore, ecosystems cannot survive unless atoms and resources are recycled
The Carbon Cycle recycles carbon throughout the ecosystem
This is done as there is a finite supply of carbon on the planet
Various processes return carbon to the air, such as respiration and combustion
Only one process retrieves carbon (in the form of carbon dioxide) from the air, which is photosynthesis
Humans have had a large impact on the atmospheric levels of carbon dioxide through activities suchas deforestation and combustion
We can begin to restore the balance of carbon dioxide in the air by using sustainable fuels and promoting reforestation