This question is about the cycling of water and carbon in ecosystems - AQA - GCSE Biology Combined Science - Question 1 - 2022 - Paper 2

1. Evaporation - Water from surfaces turns into vapor.

2. Condensation - Water vapor cools and turns back into liquid.

3. Precipitation - Water falls to Earth in the form of rain, snow, etc.

4. Drainage - Water running off from surfaces and returning to water bodies.

5. Transpiration - Water is released into the atmosphere from plants.

To calculate the number of people with severe water shortage, we use the formula:

$ext{Number of people} = ext{Total population} \times \frac{4.5}{100}$

Substituting the values gives:
$6,000,000,000 \times 0.045 = 270,000,000$

In standard form, this is written as $2.7 \times 10^8$.

Climate change has increased the area of deserts. This leads to reduced freshwater resources.

More water is used to grow crops. The demand for water in agriculture is rising with population growth, increasing competition for the available supply.

Microorganisms in the soil, such as bacteria and fungi, decompose the fallen leaves. During this process, they break down complex carbon compounds into simpler substances. This process not only releases carbon dioxide back into the soil but also makes nutrients available for other plants, allowing carbon to be reused for new plant growth.

One significant benefit is that nitrates are released into the soil. This enriches the soil with essential nutrients, promoting better growth for living plants.