Earth's life support, the carbon cycle

Lesson overview

This introductory lesson looks at the scientific processes and concepts of the carbon cycle. This will enable students to grow prior knowledge of food chains and feeding relationships to understand the drivers of environmental change. The lesson starts with an introduction to what carbon is, followed by a scaffolded understanding of the carbon cycle, reinforced by a fun activity. The lesson will close by analysing how an imbalance in the carbon cycle is leading to increased carbon in the atmosphere, which is driving the climate crisis.

Learning outcomes
  • Know what carbon is and where to find it
  • Understand how carbon moves through the carbon cycle
  • Link changes in the carbon cycle to human activity
Lesson steps

1. What is carbon? (10 mins)

This lesson focuses on carbon, the carbon cycle, and how changes in the carbon cycle from human activity are driving climate change. Slide 2 introduces the idea of the carbon cycle, and then slide 3 introduces the learning objectives. Slides 6 to 10 involve a carbon quiz. This section aims to show that carbon is found in many different places and in many different forms. Review the quiz using slide 11.

In terms of subject knowledge and the questions on slides 7 to 10:

  • Carbon is found in breath as carbon dioxide
  • Diamonds are pure carbon
  • Fizzy drinks contain carbon dioxide, both dissolved and as bubbles
  • Hands (and all animals!) are an example of living carbon
  • Clothing can be made from polyester and other synthetic fabrics made from oil from dead plants that have transformed over millions of years under great pressure and heat
  • Pencil leads are made from graphite, a form of pure carbon
  • Coal is a fossil fuel formed from dead plants
  • Trees (and all plants and algae) are an example of living carbon

2. How does carbon move? (5 mins)

The first stage in understanding the carbon cycle is to relate the concepts and processes that students have previously studied. Slide 13 introduces the idea of the carbon cycle. Students may have come across some of the ideas presented in the subsequent slides which describe some of the basic processes in the carbon cycle.

Slide 14 starts with plants absorbing carbon dioxide from the atmosphere. Students may have come across this when learning about what plants need to survive. To extend student knowledge, you could mention the concept of photosynthesis at this stage, whereby plants ‘use’ carbon dioxide and water to create sugars, powered by the sun’s energy.

Slide 15 shows how plants then return carbon dioxide when they use this food to grow and for energy. This is the process of respiration and takes place in humans and other animals too.

Slide 17 brings in the idea of the transfer of carbon from feeding. Students may have come across this with the study of food chains.

Slide 18 completes these basic processes by bringing in the fact that animals release carbon dioxide into the atmosphere. This is the process of respiration where energy is released from sugars when combined with oxygen, producing carbon dioxide and water.

3. What is the carbon cycle and how has it changed? (15 mins)

Use Slide 19 to show how these processes come together into a basic model of the carbon cycle, and slide 20 brings in the ocean and its life. Slides 21 to 26 then describe how human activity has changed the carbon cycle, with an emphasis that this is because carbon is in the ‘wrong place’ rather than being inherently bad. This section ends with a quick Student Sheet based test.

4. Carbon cycle role play activity (15 mins)
This section consolidates the learning so far through a role play activity. There is an accompanying Activity Overview with further details on how to set up this activity and run it. The carbon cycle role play activity is an active modelling of the journey of carbon between plants, animals, the atmosphere, and fossil fuels over the past 750 years.

The important learning is for students to understand the movement of carbon, and how the burning of fossil fuels since industrialisation has meant that there is now more carbon in the atmosphere.

Slides 28 to 44 support this activity. The student icons show how many students start in each place, and then move on each round. Slide 43 shows the number of students at the end of the role play activity. The ‘missing’ fossil fuel carbon is shown as greyed out and added to the atmosphere and ocean shown in red.

Review the activity using the questions on slide 44. If you wish to extend this learning there are detailed carbon cycle diagrams and descriptions on slides 48 to 55.

5. Why does this matter? (5 mins)

This section looks at the relationship between carbon in the atmosphere and global average temperatures. Use Slide 43 to link carbon dioxide and the temperature rising and link the rapid rise of carbon dioxide in the atmosphere to what students experienced during the role play activity.

This graph shows two lines. In blue, it shows the levels of carbon dioxide in the atmosphere in parts per million (ppm). The black line shows temperature anomaly in degrees Celsius. This is how much the global temperature has changed from the long-term average. Students may notice that the two lines start increasing more rapidly over the past 250 years. Students should be able to link the increase in carbon dioxide to the burning of fossil fuels. Students may also know about how increased levels of carbon dioxide in the atmosphere are causing global heating.

6. Learning review (5 mins)

This final section asks students to reflect on their learning by completing a review pyramid.