Tuesday, 21 June 2011

4.10 Nitrogen Cycle

describe the stages in the in the nitrogen cycle, including the roles of nitrogen fixing bacteria, decomposers, nitrifying bacteria and denitrifying bacteria
Nitrogen consists of 78.324% of the atmosphere
Unreactive, abundant

Uses of nitrogen in plants:
Plant takes in N03(Nitrates) to make amino acids(CHON) and then made into protein. DNA contains nitrogen.

How does nitrogen in the atmosphere transfer into the soil?
Lightening can combine atmospheric nitrogen and oxygen to form nitrate, lightening has sufficient energy to do so however, this is rare, does not give enough nitrates for plants to grow.

Food Chain
Nitrogen can pass through trophic levels in the form of protein.

In animals the urea+water=>urine which is a return of nitrogen to the soil

Decomposers can take urine/urea along with the decaying organic molecules and break them down to ammonia (NH3) However, this cannot be used for growth of plants.

Nitrifying bacteria
It changes NH3 (ammonia) into No2-(nitrite) and then into No3 (nitrate) which can be used

Freeliving Bacteria
Freeliving bacteria in the soil (not directly related to the plant) can turn atmospheric nitrogen into nitrate in the soil that plant uses. N2=>NO3-

There are some plants structures on the roots called nodules, e.g. Legumi (beans, clover), these are capable of taking atmospheric nitrogen into nitrate.

Denitrifying bacteria
They take nitrate back to nitrogen.

4.9 Carbon Cycle

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

In photosynthesis:
Co2+H2O==chlorophyll & light > C6H12O6+O2
Carbon dioxide+Water using light energy and chlorophyll turns into glucose and oxygen
[Carbon consists of 0.03% of the atmosphere]  [Oxygen is know for reducing the amount of carbon in the atmosphere]

Passage of carbon through the various trophic levels
Produce => Primary Consumer (takes carbon from the producer to grow) => Secondary consumer (carbon passes along)

Aerobic Respiration:
[Respiration adds CO2 to the atmosphere]
All organisms are giving off carbon dioxide to the atmosphere through the process of respiration

All of the organisms will die at some point and the organic molecules are broken down by decomposer organisms (bacteria, fungi) which will result to carbon dioxide being released back to the atmosphere.

Fossil fuels (oils, coals)==combustion> Carbon Dioxide
Industrial uses can contribute a lot of carbon dioxide to the atmosphere but so does motor vehicles (airplanes, cars, lorries etc.)
Naturally- Lighting striking vegetation can cause forest fires or grassland fires

Diagrams of carbon cycles:

Thursday, 9 June 2011

4.14 Enhanced Greenhouse Effect

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

Pollution (CO2, CH4, water vapour) can increase the concentration of greenhouse gases in the atmosphere and the infra red will increasing be re-emitted back into the surface instead of being reflected off. The consequences of this is that the average global temperature will increase = GLOBAL WARMING.
Consequences can include ice caps melting resulting in higher sea levels, which will change the ocean current, alter the wind direction, possibly more extreme weather and contribute to Climate Change. Which can change the world distribution of biomes.
polar ice caps melting

4.13 Greenhouse gases

Understand how human activities contribute to the greenhouse gases.

Human activities such as burning of fossil fuels result in more formation of carbon dioxide, nitrous dioxides and sulphur dioxides (Co2,NO2,SO2). Burning of fossil fuels could be burning coal in coal fire power stations, vehicles burning petroleum and can be categorized into Industrial, Cars, Domestic Combustion. Farming such as cattle ranching can emit methane (CH4) gas to the atmosphere (9% estimated), crops rotting could also increase the amount of methane in the atmosphere. Evaporation of water turning them into water vapour also contributes a lot to the greenhouse gas. Refrigeration/Solvent/CFC[combination of chlorine,carbon,fluorine] are catalysing the break down of the ozone layer. (is not a greenhouse gas though)
% of Human Contributed Greenhouse gases by sector

4.12 Greenhouse Effect

Recall water vapour, carbon dioxide, nitrous oxide, methane and CFCs (chlorofluorocarbon) are green house gases
As shown in the diagram when infra red rays come from the sun come rays could be reflected back into space (50%), turned from UV into Infra Red rays on the surface (available as heat) or trapped in our atmosphere by green house gases. What greenhouse gases does is when infra red rays get reflected back out the space the infra red rays could hit greenhouse gases, it will absorb the energy and re-emitt the infra red but also re-distributes the energy back into the surface which increases the surface temperature. Enhanced greenhouse effects refers to the thickening of the greenhouse gas layer through pollutants such as carbon dioxide, methane which will absorb more infra red which will raise the temperature and can lead to climate change.CFCs deplete the ozone layer (O3) into O2, O3 is good at absorbing UV light and depleting it means more UV light will get to the surface. [CCl2F=sunlight>CCLF+CL-] Sources of CFCs are aerosols, air conditioner, refrigeration etc.

4.11 Gas Pollution

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

Sulphur Dioxide (SO2) is a gas is added to the atmosphere by the combustion of fossil fuels in power stations, factories etc. Vehicles also contribute a lot of sulphur dioxide to the atmosphere. When sulphur dioxide rises up in the atmosphere it forms sulphuric acid with water which condenses as clouds(SO2+H2O=>Sulphuric Acid) and falls as acid rain. Acid rain can 'burn' tree when fallen and the sulphuric acid causes Calcium and Magnesium to be leached out of the soil, without calcium and magnesium ions in the soil the plants will cause the leaves to turn yellow/wither and the plant can't grow. The precipitation will form streams and goes to the lake which will reduce the ph of the lake (because its acidic) the affect is that it brings the release of aluminium ions (Al3+) which causes the thickening of mucus in the fishes gills which reduces the ability of fish to obtain oxygen through water and the fish suffocates and dies.

photo showing plants affected by acid rain

sulphur dioxide coming from coal power plants.

trees 'burned' by acid rain

Carbon Monoxide (CO) is a gas added to the atmosphere by the combustion of fossil fuels (more particularly coal) burned with insufficient oxygen. Carbon monoxide combines with our haemaglobin inside our blood to form carbamina haemaglobin and blocks haemaglobin from carrying oxygen which reduces oxygen circulation. This is toxic, too much carbon monoxide can be fatal.