AQA GCSE FOUNDATION Biology: Carbon Cycle and Nutrient Cycling

AQA GCSE Foundation Biology: Carbon Cycle and Nutrient Cycling

Essential Cycles Supporting Life

The Carbon Cycle

The carbon cycle is a continuous process that moves carbon through the Earth's systems. It's essential for life, as carbon is the building block for all living organisms. Here's a breakdown of the key steps:

1. Photosynthesis: Plants and algae take in carbon dioxide from the atmosphere and use it to create sugars for energy during photosynthesis.

2. Respiration: All living organisms, including plants and animals, breathe in oxygen and release carbon dioxide as a byproduct of respiration.

3. Decomposition: When organisms die, decomposers (like bacteria and fungi) break down their bodies. This process releases carbon dioxide back into the atmosphere.

4. Fossil Fuels: Over millions of years, dead organisms can be compressed into fossil fuels (like coal, oil, and natural gas). These fuels contain stored carbon.

5. Combustion: When fossil fuels are burned, carbon dioxide is released into the atmosphere.

6. Oceanic Carbon: The oceans absorb a significant amount of carbon dioxide from the atmosphere. This carbon can be used by marine organisms or stored in the ocean floor.

7. Volcanic Activity: Volcanoes release carbon dioxide from the Earth's interior into the atmosphere.

Key Concepts:

• Carbon Sink: A place where carbon is stored for a long period, like forests or the ocean.
• Carbon Source: A place where carbon is released into the atmosphere, like burning fossil fuels.

Nutrient Cycling

Nutrient cycling refers to the continuous movement of essential nutrients, like nitrogen, phosphorus, and potassium, through different parts of the ecosystem. These nutrients are vital for plant growth and, consequently, for all life.

1. Nitrogen Cycle:

• Nitrogen gas is abundant in the atmosphere.
• Nitrogen-fixing bacteria convert atmospheric nitrogen into a usable form by plants.
• Plants absorb nitrogen and use it to build proteins and other molecules.
• Animals obtain nitrogen by consuming plants.
• Decomposers break down dead organisms, releasing nitrogen back into the soil.
• Denitrifying bacteria convert nitrates back into nitrogen gas, returning it to the atmosphere.

2. Phosphorus Cycle:

• Phosphorus is found in rocks.
• Weathering and erosion release phosphorus into the soil.
• Plants absorb phosphorus from the soil.
• Animals get phosphorus by eating plants.
• Decomposers release phosphorus back into the soil.
• Phosphorus can be lost from the cycle if it gets washed into waterways and settles in sediments.

3. Potassium Cycle:

• Potassium is also found in rocks.
• Plants absorb potassium from the soil.
• Animals obtain potassium by consuming plants.
• Decomposers release potassium back into the soil.
• Potassium can be lost from the cycle if it gets washed into waterways and settles in sediments.

Key Concepts:

• Nutrient Deficiency: Plants may suffer from nutrient deficiency if the soil lacks certain nutrients.
• Fertilizers: Farmers use fertilizers to add nutrients to the soil, helping plants grow.

Human Impact:

Human activities can significantly disrupt the carbon and nutrient cycles:

• Deforestation: Reduces the amount of carbon stored in trees, increasing atmospheric carbon dioxide levels.
• Burning Fossil Fuels: Releases large amounts of carbon dioxide into the atmosphere, contributing to climate change.
• Pollution: Can disrupt nutrient cycles, leading to imbalances and negative impacts on ecosystems.

Understanding these cycles is crucial for appreciating the interconnectedness of life on Earth and for taking steps to protect our planet.