nutrient cycles

Question 1

describe the carbon cycle

Answer 1

1. CO2 removed form atmosphere by green plants & algae during photosynthesis.
   * Carbon used to make glucose, which can then be turned into carbohydrates, fats, proteins, that make up the body of plants & algae.
2. When plants & algae respire, some carbon returned to atmosphere.
3. When plants & algae eaten by animals, some carbon becomes part of the fats and proteins in their bodies
4. When animals respire, some carbon is returned to atmosphere as CO2.
5. When plants, algae, animals die – decomposers feed on their remains, waste materials (urine, faeces.)
   * Decomposers can be some type of animals/microorganisms.
   * When decomposers respire, they release CO2 in air again.
6. Not at all organic material decomposes - some dead organisms have been compressed over millions of years, forming fossil fuels (coal, oil, natural gas)
7. Combustion of wood & fossil fuels also releases CO2 back into air.
   - when they’re burnt, CO2 in them combines w oxygen in air
8. carbon cycle constantly being cycle from air, food chains, back into air again.

Question 2

describe nitrogen cycle

Answer 2

Nitrogen fixation occurs in these 2 main ways:
1. Lightning: makes nitrogen gas in air combine with oxygen. Forms nitrates.
2. Nitrogen-fixing bactera: in soil and roots of some plants.
- Plants absorb these ions from soils & use the nitrogen in them to produce amino acids, which join together to make proteins
- Nitrogen is then passed along food chains in the form of proteins, as animals eat plants (& each other.)
- When proteins are digested, they’re converted back t amino acids.
- Deamination occurs in the liver in animals.
- Ammonia is a waste product from deamination, which gets converted to urea then excreted.
- The urea is then decomposed and nitrogen ions are returned to the soil.

Question 3

what are the 4 types of microorganisms involved in nitrogen cycle

Answer 3

Decomposers
* break down proteins (in rotting plants/animals) & urea (animal waste) & turn them to ammonia. Forms NH4+ (ammonium ions) in the soil.

Nitrifying bacteria
* Turn ammonium ions in decaying matter to NO2- (nitrate ions) and then nitrates. This is nitrification.

Nitrogen-fixing bacteria (in soil and roots of plants)
* Turn atmospheric N2 into nitrogen compounds that plants can use (e.g ammonia/nitrate ions)

Denitrifying bacteria
* Turn nitrates back into N2 gas (dentrification) has no benefit to organisms.