6.5.4(Recycling within ecosystems)

Describe what is meant by decomposers

• They are Saprotrophs which can digest cellulose

• Secrete enzymes outside of their bodies and absorb the products of digestion

• Absorbed substances are used for respiration

Describe what Detritivores are

• They cannot break down cellulose

• Breakdown dead matter into smaller pieces creating a larger surface area for enzymes to work

state 2 processes which removed carbon dioxide from the air

• Photosynthesis by plants

• Dissolving in the oceans

State 4 processes which return carbon dioxide to the air

• Respiration by plants, animals and microbes

• Combustion of fossil fuels such as coal, oil and gases

• Weathering of limestone of chalk

• Thermal decomposition of limestone

Describe the process of thermal decomposition of limestone

• Breaking down using heat

• Calcium carbonate(chalk and limestone) → Carbon dioxide + Calcium oxide

• CaCO3 → CO2 + CaO

State what thermal decomposition of limestone is used for

• Used in the manufacture of cement

Describe what is meant by a carbon sink

• Parts of the carbon cycle which store carbon

State the mineral ions released when breaking down these different molecules:

1. Chlorophyll

2. Phospholipids

3. Proteins

4. Nucleic acid

1. Chlorophyll: Magnesium ions

2. Phospholipids: Phosphate ions

3. Proteins: Nitrate ions

4. Nucleic acids: Nitrate ions

State the 3 main steps in the nitrogen cycle

1. Saprotrophic digestion: Decomposers digest proteins → amino acids

2. Ammonification: Amino acids → Ammonium compounds

3. Nitrification: Conversion of ammonium compounds → nitrates

Describe the process of saprotrophic digestion

• Saprotrophic decomposers secrete enzymes onto organic molecules, which break down larger molecules into smaller molecules which are absorbed into bodies of decomposers

• Fungi and bacteria break down proteins into amino acids Some are absorbed, some remain outside them

Describe the process of ammonification

• When plants die and decay decomposers break down their proteins, releasing ammonia

• Animal wastes, urea and faeces all contain nitrogen and saprotrophic microorganisms also feed on these to release ammonia

• Ammonifying bacteria convert ammonia to ammonium ions which is stored in the soil

Describe the process of nitrification

• Aerobic Nitrifying bacteria get energy from reactions involving inorganic ions -

• Ammonium ions → nitrate ions

• This process is oxidisation of ammonium ions and occurs in soil with air pockets

• Stages:

  1. Ammonium ions converted into nitrite ions by Nitrosomonas

  2. Nitrite ions converted into nitrate ions by Nitrobacter

Describe the process of denitrification

• This occurs when soils become water logged

• The denitrifying anaerobic bacteria use NO3- as an electron acceptor for respiration instead of O2 with the product being N2

• NO3- → N2

• Nitrate is reduced to N2 and returned to the atmosphere

Describe the process of nitrogen fixation

• Nitrogen gas from the atmosphere can be converted to ammonia or ammonium ions

• Which can occur when lighting occurs and through bacteria in the soil

  • Azotobacter - produce ammonium ions from nitrogen gas.

  • Rhizobium - Live on root nodules. They get glucose from the plant and they provide ammonium ions by converting N2 gas into ammonium ions to the plant

Explain how nitrogen-containing compounds are returned to the soil

• Fungi / bacteria;

• extracellular enzymes;

• break down of organic material;

• deamination / ammonification;

Describe how the death and decay of mosses and lichens leads to an increase in the availability of nitrates.

• nitrogen-containing compounds are converted

  ammonium ions during ammonification of organic

  compounds;

• ammonium ions converted to nitrite, by Nitrosomonas;

• nitrite converted to nitrate by Nitrobacter;