Nutrient Cycles

Summary and Exam Tips for Nutrient Cycles

Nutrient Cycles is a subtopic of Organisms and their Environment, which falls under the subject Biology in the Cambridge IGCSE curriculum. Nutrient cycles, specifically the carbon cycle and nitrogen cycle, are essential processes that recycle finite resources on Earth. In the carbon cycle, carbon dioxide is absorbed by plants for photosynthesis and transferred to animals through feeding. It returns to the atmosphere via respiration and combustion of fossil fuels. Human activities like increased fossil fuel use and deforestation exacerbate carbon emissions.

The nitrogen cycle involves nitrogen fixation by bacteria and lightning, converting $\text{N}_2$ gas into absorbable forms like nitrates. Plants use these nitrates to synthesize proteins, which animals then consume. Decomposition and nitrification return nitrogen to the soil, while denitrifying bacteria convert nitrates back to $\text{N}_2$ gas, completing the cycle. Farmers can mitigate denitrification by aerating soil. Understanding these cycles highlights the importance of microorganisms and human impact on nutrient availability.

Exam Tips

• Understand Key Processes: Focus on the steps of the carbon and nitrogen cycles, such as photosynthesis, respiration, and nitrogen fixation. Knowing these processes helps in explaining how nutrients are recycled.

• Microorganisms' Roles: Remember the roles of microorganisms in the nitrogen cycle, including decomposition, nitrification, nitrogen fixation, and denitrification. This is crucial for exam questions on nutrient recycling.

• Human Impact: Be prepared to discuss how human activities like deforestation and fossil fuel combustion affect the carbon cycle. This is often a topic in exam questions related to environmental impact.

• Visual Aids: Use diagrams to visualize the cycles. This can help in retaining the sequence of processes and understanding the flow of nutrients.

• Practice Questions: Regularly attempt practice questions to test your understanding and application of these cycles in different scenarios.