(i) State what is meant by the term greenhouse effect.
(ii) Explain how deforestation (clearing forests) increases the concentration of carbon dioxide (CO2\text{CO}_2CO2) in the atmosphere, and describe the impact of this on global temperatures.
The release of pollutant gases into the atmosphere has various harmful effects on the environment and human health. Complete the table below by finding the missing gases, sources, or effects (i) to (v).
| Gas | Source | Environmental/Biological Effect |
|---|---|---|
| Methane | (i) | Contributes to global warming |
| (ii) | Incomplete combustion of hydrocarbon fuels | Binds to haemoglobin, reducing oxygen transport |
| Sulfur dioxide | Combustion of coal containing sulfur impurities | (iii) |
| Carbon dioxide | Combustion of fossil fuels and deforestation | (iv) |
| (v) | Leakage from old air conditioning units and refrigerators | Depletion of the ozone layer |
44 exam-style questions on Edexcel IGCSE Biology Human influences on the environment. Each one has a worked solution and a mark scheme showing where the marks go.