Nutrient Recycling

Ecology Chp 4+5

Nutrient recycling

the conversion of mineral elements such as carbon and nitrogen back and forth between abiotic and biotic for use in the ecosystem

Carbon cycle

the way in which carbon is taken from and added to the environment by organisms

Describe the main steps in the carbon cycle:

• plants take in CO₂ through stomata for photosynthesis to make food (carbohydrates)

• plants die and either:

  • incomplete decay leads to the formation of fossil fuels

  • they are consumed by animals; plant proteins are assimilated to form animal proteins

• animals consume plants and respire which releases Co₂

• the animals die and either:

  • incomplete decay leads to the formation of fossil fuels

  • they are decomposed by micro-organisms, which release CO₂ as they respire

• bones, teeth and shells decay by slow weathering to produce CO₂

Carbon cycle diagram:

Why do we need the carbon cycle?

• supports photosynthesis + respiration

• maintain a balance, so it does not run out

Describe the main steps in the nitrogen cycle:

• nitrogen fixation: nitrogen gas is ‘fixed’/ converted into nitrates by nitrogen fixing bacteria

  • can also be converted into nitrates by lightning which splits nitrogen molecules allowing them to join with oxygen

• nitrates are absorbed and assimilated into plant proteins

• plants die and are either

  • eaten by animals and assimilated to form animal proteins

  • decomposed by decomposing bacteria, which release ammonia into the soil

• animals either

  • excrete ammonia in urea

  • decompose by decomposers, which release ammonia into the soil

• nitrification: nitrifying bacteria convert ammonia into nitrite then nitrate

  • some of this nitrate is absorbed and assimilated by plants

• denitrification: denitrifying bacteria convert nitrates back into nitrogen gas

Nitrogen cycle diagram:

Why do we need the nitrogen cycle?

• to change nitrogen into a usable form for organisms

• to maintain a balance

Why do organisms need nitrogen?

• to make proteins and enzymes