5.2 The Greenhouse effect

1. 5.2 The Greenhouse effect

2. The Carbon Cycle Carbon is one of the most important elements that are recycled in an ecosystem.

3. Inorganic carbon dioxide in the atmosphere is trapped or “fixed” as organic carbon compounds during photosynthesis. Some of the carbon is returned to the atmosphere as the plants respire. The other steps in the cycle follow the same path as food chains. As herbivores eat plants, and carnivores eat herbivores, the carbon compounds move from plants to animals.

4. Respiration by any organism in this sequence returns carbon to the atmosphere as carbon dioxide and when a plant or animal dies, carbon compounds move to detritivores and saprotrophs which may also respire. http://www.youtube.com/watch?v=U3SZKJVKRxQ http://www.youtube.com/watch?v=Xz0fn81BlIQ

5. In some conditions, plants and animals do not decay when they die. They become compressed and fossilized in a process that takes millions of years and forms fossil fuels. Vast coal, oil and natural gas deposits have been formed and the carbon trapped in these fuels cannot return to the atmosphere unless the fuels are burned. Over a very long period of time, fossil fuel formation has gradually lowered the carbon dioxide level of Earth’s atmosphere, but recently this balance has been upset.

6. Draw a labeled diagram showing stages of the carbon cycle. [5]

7. How the Greenhouse Effect Works Certain gases, including CO2 enable the atmosphere to retain heat. Without these gases in the atmosphere, the Earth’s temperature would be too low to support life. The warming effect of these gases is known as the greenhouse effect because it is works in a similar way a greenhouse works.

8. A greenhouse is made of glass, which allows shorter-wave radiation from the sun to pass through it. As the sunlight passes through the glass, the radiation is changed into heat, which has a longer wavelength. Glass is less transparent to theses long wavelengths and heat is trapped in the greenhouse, making it warmer. The greenhouse gases such as carbon dioxide, methane, and water vapor act the same way. They trap the heat and keep the temperature comfortable for life to exist.

9. Greenhouse gases, Human Activity and Global Warming Carbon dioxide forms only 0.04% of the atmospheric gases but it plays a significant part in the greenhouse effect. Other greenhouse gases include water vapor, methane, oxides and fluorocarbons (FCs). Chlorofluorocarbons (CFCs) were used in aerosols and as refrigerants but were found to damage the ozone. They were replaced with hydrofluorcarbons (HFCs), but HFCs are causing problems because they are a greenhouse gasses.

10. Human population has increased dramatically in the last hundred years. Increased population calls for an increased demand for energy in industry, transport and homes. Most of this energy demand has been met by burning fossil fuels, mainly coal, oil and gas.

11. Burning fossil fuels releases both carbon dioxide and oxides of nitrogen. Burning these fuels has raised the concentration of carbon dioxide in the Earth’s atmosphere by more than 20% since 1959

12. In the tropical regions of the world vast rainforests trap carbon dioxide through photosynthesis and have been important in maintaining the low level of carbon dioxide. We upset this balance by deforesting vast areas of forests for agriculture and timber production. 78,000 square miles are lost every year. Forest destruction has multiple effects, but most important for the atmosphere are the loss of carbon dioxide uptake and the increase of carbon dioxide released from the rotting or burnt vegetation.