4.9 Carbon Cycle

4.9 describe the stages in the carbon cycle, including respiration, photosynthesis, decomposition and combustion.

1. Photosynthesis
 When photosynthesis occurs, CO2 is used, therefore photosynthesis is responsible for reducing the atmospheric CO2

2. Feeding
 Passage of carbon through different trophic levels

3. Respiration
 Respiration produces CO2 and therefore adds more Carbon dioxide to the atmosphere

4. Decomposition
 All organisms eventually die, their organic molecules are broken down by the decomposer organisms (bacteria and fungi) this results in the release of Carbon Dioxide back into the atmosphere

5. Combustion
 Fossil fuels contain a large amount of carbon so when combusted release a large amount of CO2
 The main uses are industrial uses and also in motor vehicles
 Combustion can also happen natural through lighting and forest fires.

This diagram visually explains most of the concepts

4.14 The Enhanced Greenhouse effect.

4.14 understand how an increase in greenhouse gases results in an enhanced greenhouse effect and that this may lead to global warming and its consequences.

Pollution of Carbon dioxide, Methane and Water vapour (all greenhouse gases)
if the concentration of these increase in the atmosphere the Infra-red light will be re-emited backwaards towards the surface of earth, rather than escaping back into deep space. This will raise the average global temperature which is referred to as Global warming/

Consequences?
The Melting of Icecaps.... raised sea levels... changing ocean currents and winds
Ultimately ... Climate change.
this will result in the worlds Biome distribution changing... Deserts expanding etc.

4.13 Greenhouse gases

4.13 understand how human activities contribute to greenhouse gases.

The burning of fossil fuels results in more Carbon dioxide, and Nitrous oxide in the atmosphere which are greenhouse gases.

Farming cows causes a significant contribution of Methane from their digestion of crops (9% of the atmospheric gases)

Evapouration of water to form water vapour... Clouds are a significant contributor

Refrigeration/Solvents (CFC's) are associated with the absorption of UV light, and the breakdown of the Ozone layer

4.12 The Greenhouse Effect

4.12 recall that water vapour, carbon dioxide, nitrous oxide, methane and CFC's are greenhouse gases

This diagram explains the effect very well:

(a) is the UV light from the sun (short wavelength with high energy) 

(b) + (h) show that 50% is reflected back out into deep space (by things like clouds)

(c) represents absorption on the earth's surface, where the UV light is converted into Infra-red 
(d) shows the Infra-red (longer wavelength) being emitted back out
(e) some of this is lost out to space as heat
(f) shows the greenhouse gases (water vapour, CO₂, CH₄, etc.)

(g) The I.R. light hits the greenhouse gas and absorbs it, but then re-emits it but re-distributes it, with some of the I.R. heading back to earth

The Hypothesis of The Enhanced Greenhouse effect is that if we emit more Carbon dioxide and Methane they will absorb more of the escaping infra-red radiation and emit it back to earth, raising the temperature higher. and eventually causing Climate change.

CFC's (chlorofluorocarbon's)

 have an effect on the ozone layer (O₃)

CCl₃F à sunlight à CL₂F^- + CL^-
CL^- catalyses the breakdown of O₃ to O₂, O₃ is better at absorbing UV light than O₂ so we are basically removing the protection.

4.11 Gas Pollution

4.11 Understand the biological consequences of pollution of air by sulphur dioxide and by carbon monoxide.


Sulphur Dioxide. (SO₂)
Comes from the combustion of fossil fuels, and combustion of petrols in vehicles.
In the atmosphere Sulphur dioxide combines with water vapour in clouds and forms Sulphuric Acid! this is what is known as acid rain,

SO₂ + H2O = H₂SO₄

acid rain has many effects on plants and animals:

1. Trees and plants are often damaged by the sulphuric acid
2. Sulphuric acid in the soil causes Calcium and Magnesium Ions to become leached* out of the soil, so the plant can't grow.
3. Acid rain in lakes reduces the pH to make them acidic, this causes a release of Aluminium Ions, which causes a thickening of the mucus that lines the gills, and reduces the ability to take Oxygen from water (the fish suffocates)

Leach - Make (a soluble chemical or mineral) drain away from soil, ash, or similar material by the action of percolating liquid, esp. rainwater

• - the nutrient is quickly leached away

Carbon Monoxide (CO)

Fossil fuels i.e. Coal/gas are burned with insufficient (not enough) Oxygen

Carbon monoxide combines with Haemoglobin inside red blood cells and forms Carbaminohaemoglobin which blocks the haemoglobin  from carrying Oxygen, therefore reducing Oxygen circulation and too much can be fatal.