4.10) Nitrogen Cycle

4.10 Describe the stages in the nitrogen cycle, including the roles of nitrogen fixing bacteria, nitrifying bacteria and denitrifying bacteria (specific name of bacteria not required.)

N2 - 78.324% called atmosphere

unreactive, abundant

Plants can take in nitrogen in the form of nitrate NO3- to manufacture amino acids which combine together to form protein.

Nitrogen is also important for the formation of DNA.

How do plants get nitrate?

Lightning can combine atmosphere nitrogen with oxygen to form nitrate because it has sufficient energy for the bonding. 

N2 + 3O2 ---> 2NO3-

Use of nitrogen in plant

Plants can take in nitrate from soil or from the atmosphere.

The amino acid contains of carbon, hydrogen, oxygen, and nitrogen (CHON).

The amino acids are then built into protein.

Food chain

Producer ---> Primary consumer ----> Secondary consumer ---> .....

Nitrogen passes through the trophic level in feeding in the form of protein.

Excretion

Animal ---> nitrogen excretion, usually in the form of urea

Urea + H2O ---> Urine

This adds nitrogen back into soil.

Dead

Dead ---> decomposers

Urine/ Urea + Decaying organic molecule ---> breaks down by decomposers into ammonia (NH3)

Ammonia is converted into nitrite

NH3 (ammonia) -----convertion-----> NO2= (nitrite)

with the help of nitrifying bacteria

Plants (root system)

In the soil there's a type of free living bacteria which takes atmospheric (in the air or soil) nitrogen and turns it into nitrate. 

Leguminous plants such as Beans and clover have structure on the roots called nodules. 

nitrate ---> nitrate

Denitrifying bacteria

Presented in the soil

Take nitrate and convert it back to nitrogen.

4.9) Carbon Cycle

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

Components of cycle:

1. Photosynthesis

6CO2 + 6H2O -----light energy----> C6H12O6 + 6O2

carbon dioxide = 0.03% of the atmosphere

When photosynthesis occurred, it reduces the atmospheric carbon dioxide.

2. Feeding

Producer ----> Primary Consumer ----> Secondary Consumer

Primary consumer takes in carbon form the producer and turns it into chemical they can use to grow.

Carbon passes along the food chain.

3. Respiration (all organisms carry out respiration)

glucose + oxygen ----enzyme/cell----> energy + carbon dioxide

Respiration adds carbon dioxide to the atmosphere.

4. Decomposition (after death)

Organic molecules of dead organisms are broken down by decomposers such as bacteria and fung9

This add carbon dioxide back into the atmosphere.

5. Combustion 

- Fossil fuel (oils & coals) --------combusted-----> Carbon dioxide

example: industrial application, motor vehicles, etc.

- Natural Combustion

eg) lightning striking forest tree which leads to fire

4.14) Enhances 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 ---> CO2, CH4, water vapour (greenhouse gases)

increase their concentration in the upper atmosphere

infrared light from the planet surface will be increasingly reemitted backward into the earth surface, which raise the average global temperature = global warming

Consequences:

- melting of ice cap in polar region

- raised sea levels

- change in ocean current

- change in wind current

CLIMATE CHANGE

changes in distribution to the world's biomes and affect the ecosystems

4.13) Greenhouse gases

4.13) understand how human activities contribute to greenhouse gases

Burning of fossil fuels (from factories and vehicles/ industrial process/ domestic combustion) ---> SO2+ CO2/ NO2 = green house gases --- absorbs infrared rays and reemit them back to earth

Farming 

- animal such as cows can emit methane gas to the atmosphere, which provide 9%

Evaporation of water ---> water vapour

Clouds are water vapour

Refrigeration/ Solvents/ Propellant --- CFC --- chlorine, carbon, fluoine--- CCl3F

absorbs ultraviolet light and catalyst the breakdown of ozone layer

4.12) Greenhouse effect

4.12 recall that water vapor, carbon dioxide, nitrous oxide, methane and CFCs are greenhouse gases

UV light came from sun ---- short wavelength & high energy

50% of UV light is reflected by clouds back into space

50% is being absorbed by the earth surface in which the UV light is converted into infrared rays

infrared rays has longer wavelength and some is lost into the space by heat

Greenhouse gases = water vapour, CO2, methane (CH4)

Infrared light hits the greenhouse gas in which the energy is absorbed and spread the ray to all direction, which reemits infrared and redistribute some gases going downward. This keeps the earth warm and raise its temperature.

Enhanced greenhouse effect

If we increase CO2 and CH4, they will absorb more infrared rays which leads to increase in temperature. This can result in climate change.

CFC - Chlorofluorocarbon - effect zone layer (O3)

- Carbon

- Fluorine

- Chlorine

CCL3F -----sunlight----> CCO2F(-) + Cl(-)

notice ions formed

Cl(-) breaks O3 down into O2.... but O3 is much better in absorbing UV light. We are losing the protection of the ozone effect.

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

1. Sulphur dioxide - SO2 gas

added to atmosphere when we have combustion of fossil fuels, such as coals and irons, from factories and vehicles

SO2 + H2O ---> Sulphuric acid ---> condenses into cloud and turn into acid rain in the form of precipitation

acid rain affects plant by....

- dry deposition -- "burned" the leaves of plants (by gases)

- wet deposition -- causes calcium and magnesium, to be leached out of the soil, this means plants won't be able to absorbs these minerals

if acid rain runs into steam....

- reduce pH (make them acid)

- release of aluminum acid --> causes thickening of the mucus and reduces the fish's ability to take oxygen from water (kills the fish)

2. Carbon monoxide - CO gas

added when fossil fuels such as coal or gas are burnt with insufficient oxygen (incomplete combustion)

combines with hemoglobin inside the red blood cell and forms a molecule called carbamina haemoglobin ---- blocks haemoglobin from carrying oxygen which reduces oxygen circulation (very difficult to release the gas from haemoglobin)

carbon monoxide is a toxic gas and can be fatal