Identify and describe What is Decomposition?, Factors Affecting the Rate of Decay and Effect of Temperature on Decomposition in the context of decomposition (biology only).
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GCSE Biology Revision
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GCSE Biology revision
Decomposition (biology only)
Organisation of an ecosystem
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Explain the relationships between What is Decomposition?, Factors Affecting the Rate of Decay and Effect of Temperature on Decomposition and how they contribute to decomposition (biology only).
Apply and analyse knowledge of What is Decomposition?, Factors Affecting the Rate of Decay and Effect of Temperature on Decomposition to interpret unfamiliar information about decomposition (biology only).
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What is Decomposition?
- Decomposition is measured by the rate of decay, which is the speed at which decomposers break down dead organisms.
- Decomposers are organisms that break down dead organic matter, releasing nutrients back into the environment.
Factors Affecting the Rate of Decay
- The three main factors affecting the rate of decay are temperature, water availability, and oxygen availability.
- Each factor influences how efficiently decomposers can carry out their biological processes.
Effect of Temperature on Decomposition
- Decomposers have an optimum temperature at which their enzymes work most efficiently, just like all enzymes.
- If the temperature is too low, decomposer enzymes work too slowly, reducing the rate of decay.
- If the temperature is too high, the enzymes denature due to heat breaking weak hydrogen bonds, altering the tertiary structure and causing the rate of decay to drop dramatically.
Effect of Water on Decomposition
- Water is essential for decomposition because some decomposers secrete enzymes onto dissolved organic matter and absorb the products.
- If decomposers are starved of water, the rate of decay decreases, whereas plentiful water supports a high rate of decay.
Effect of Oxygen on Decomposition
- Oxygen is generally required for decomposers to respire aerobically, and as more oxygen becomes available, the rate of decomposition increases.
- Some decomposers can also function in anaerobic conditions, breaking down organic matter without oxygen.
Calculating the Rate of Decay
- The rate of decay is calculated using the formula: Rate of decay = (change in mass (g)) / (time (hours)), giving units of grams per hour (g/hr).
- For example, a mass decrease from 200 g to 130 g over 30 hours gives a rate of decay of (200-130) / (30) = 2.33 g/hr (to 3 significant figures).
- If data is plotted on a graph, the rate of decay can be found by calculating the gradient using gradient = (rise) / (run), measuring between two points as far apart as possible.
Compost and Farming Applications
- Compost is the product of decomposed dead plants and acts as a natural fertiliser for crops.
- Adding worms to compost increases the rate of decomposition, improving the quality and speed of compost production.
- The most important element recycled through decomposition is nitrogen, which is converted into nitrate ions essential for protein synthesis in plants.
Biogas and Anaerobic Decomposition
- Anaerobic decomposition by decomposers in the absence of oxygen produces methane gas, which can be used as a fuel.
- A biogas generator uses manure or specific organic crops as feedstock, and the anaerobic decomposition produces methane that can be combusted as an energy source.
Common Misconceptions About Decomposition
- Decomposition is an ongoing process and does not only begin after the death of a crop or animal — it is continuous.
- To calculate the rate of decay, both the change in mass and the time period over which the change occurred are needed, not just the change in mass alone.
- There is such a thing as too hot for a decomposer — excessively high temperatures cause enzyme denaturation, reducing the rate of decay.