Global warming — AQA GCSE Biology
Test yourself on Global warming with AQA GCSE practice questions.
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Global warming explained
Global warming is the rise in average global temperature caused by increasing greenhouse gases such as carbon dioxide and methane.
Read the full explanation
Its biological consequences include changes to the distribution of species as they move towards cooler areas, loss of habitat for species that cannot move, and changes in the timing of life cycles such as migration, breeding and flowering. Warmer oceans and melting ice reduce habitats for polar species, while some pests and disease-carrying insects may spread into new areas. Biodiversity can fall if species cannot adapt or relocate quickly enough. These effects are described and explained using named examples.
Levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to ‘global warming’.
Carbon dioxide and methane are greenhouse gases. Their levels in the atmosphere are rising because of human activities: burning fossil fuels releases carbon dioxide, while agriculture, landfill and fossil fuel extraction release methane. Greenhouse gases absorb infrared radiation emitted by the Earth and re-radiate some of it back, so less heat escapes to space and the average global temperature rises. This is the greenhouse effect, and the resulting increase in temperature is called global warming. More carbon dioxide and methane therefore strengthen the greenhouse effect and contribute to global warming.
Your focus
- Describe biological consequences of global warming for species and habitats.
- Explain how changes in temperature can affect the distribution and life cycles of organisms.
- Link global warming to reduced biodiversity and increased extinction risk.
Show all 6 objectives
- State that carbon dioxide and methane are greenhouse gases whose atmospheric levels are increasing.
- Describe how greenhouse gases absorb and re-radiate infrared radiation.
- Explain how increasing greenhouse gas levels contribute to global warming.
Global warming exam tips
Marking Points
- Global warming is a rise in average global temperature caused by increasing greenhouse gases.
- Species may shift their distribution towards cooler areas or higher altitudes.
- Some species cannot move or adapt quickly enough and may become extinct, reducing biodiversity.
- Changes in temperature can alter the timing of migration, breeding and flowering.
- Melting ice and warmer oceans reduce habitats for species such as polar bears and corals.
- Pests and disease-carrying insects may spread into new areas as conditions change.
- These consequences can be described using named examples of species or habitats.
- Carbon dioxide and methane are greenhouse gases.
- Burning fossil fuels releases carbon dioxide into the atmosphere.
- Agriculture, landfill and fossil fuel extraction release methane.
- Greenhouse gases absorb infrared radiation emitted by the Earth.
- Some of this radiation is re-radiated back towards the Earth, so less heat escapes.
- This strengthens the greenhouse effect and raises average global temperature.
- The rise in average global temperature is called global warming.
Examiner Tips
- 💡Name a specific species or habitat when describing a consequence to make the answer precise.
- 💡Use words such as distribution, migration and biodiversity to show biological understanding.
- 💡If asked to describe, give several distinct consequences rather than repeating one idea.
- 💡Name both carbon dioxide and methane and give a source for each.
- 💡Explain the greenhouse effect in steps: absorption, re-radiation, less heat escaping.
- 💡Use the phrase average global temperature rather than just saying the weather gets hotter.
Common Mistakes
- Confusing global warming with the ozone hole; correction: global warming is caused by greenhouse gases trapping heat, while ozone depletion is a separate issue.
- Saying all species will simply move and survive; correction: some cannot move or adapt quickly enough and may become extinct.
- Describing only temperature rise without a biological consequence; correction: link the temperature change to effects on species, habitats or life cycles.
- Thinking the greenhouse effect is entirely harmful; correction: a natural greenhouse effect keeps Earth warm enough for life, but extra gases strengthen it.
- Confusing global warming with ozone depletion; correction: they are separate processes caused by different gases.
- Believing carbon dioxide is the only greenhouse gas; correction: methane is also a greenhouse gas and its level is increasing.