BIOLOGY · Stage 9 · Chapter 12: The Carbon Cycle and Climate Change
Biology 12.6 Chapter 12 Review: The Carbon Cycle and Climate Change
5 min read 5 parts Lesson 6 of 6
Lesson summary
12.6 Chapter 12 Review: The Carbon Cycle and Climate Change — Alhussan International Academy — Biology (Stages 7–9) notes: Revise how carbon moves through the environment, how people alter it and how scientists study and predict climate change.Exchange — carbon moves between the …
- Photosynthesis
- Respiration
- Decomposition
- Combustion
- Fossil fuels
- Deforestation
Section 1 of 5The carbon cycle
- Exchange
- carbon moves between the atmosphere, living things, soil, oceans and rocks.
- Photosynthesis
- it removes carbon dioxide from the air and builds it into glucose.
- Feeding
- it passes carbon compounds along food chains.
- Respiration
- plants, animals and microorganisms return carbon dioxide to the air.
- Decomposition
- decomposers break down dead matter and release carbon dioxide.
- Combustion
- burning wood and fossil fuels releases carbon dioxide quickly.
- Fossil fuels
- dead organisms buried for millions of years form a long-term store of carbon.
Section 2 of 5Human impact and the enhanced greenhouse effect
- Fossil fuels
- burning coal, oil and gas moves carbon from a long-term store into the atmosphere in a short time.
- Deforestation
- it reduces photosynthesis and, if trees are burned or decay, releases stored carbon.
- Methane
- livestock and rice paddies add it.
- Enhanced greenhouse effect
- extra carbon dioxide and methane absorb more infrared radiation re-emitted by the Earth, so the planet warms.
- Concentration
- carbon dioxide has risen from about 280 ppm to over 420 ppm.
Section 3 of 5Explaining the greenhouse effect
- Energy from the Sun passes through the atmosphere and warms the Earth's surface.
- The warm surface radiates heat back towards space.
- Carbon dioxide and other greenhouse gases absorb and re-emit some of that heat.
- A higher concentration traps more energy, so the surface temperature rises.
Section 4 of 5Effects of climate change
- Warming
- the atmosphere and oceans warm and glaciers and ice sheets melt.
- Sea level
- it rises from melting land ice and thermal expansion, threatening low-lying coasts.
- Extreme weather
- more heatwaves, droughts, floods and stronger storms.
- Habitats
- habitats and the distribution of species change, and corals bleach.
- Rate
- past climate changes happened naturally over thousands of years, while current changes are faster and linked to human emissions.
Section 5 of 5Evidence and models
1Evidence2 points
- thermometer and satellite records, ice cores, tree rings and pollen.
- A claim is more reliable if it uses long-term data from many sources, has been peer reviewed and is repeated by others.
2Climate models3 points
- they use equations for the atmosphere, oceans and ice to project future temperatures under different emission scenarios.
- They are tested against past records (hindcasting).
- Predictions have a range because the future depends on human choices and on feedbacks.
| Idea | Key point |
|---|---|
| Mitigation | Reduce emissions: renewable energy, efficiency, protect forests |
| Adaptation | Cope with change: sea walls, drought-resistant crops |
Last updated: