23.3 recycling within ecosystem

What is decomposition

A chemical process in which a compound is broken down into smaller molecules, or its constituent elements

What are organisms are usually decomposers?

Bacteria and fungi

What are saprotrophs?

Organisms that obtain their energy from dead or waste organic material

How do saprotrophs digest food

-Externally by secreting enzymes onto dead organisms
-the enzymes break down complex organic molecules into simpler soluble molecules, which are absorbed by the decomposers

What are detritivores

Organisms that feed on dead, decaying matter

What is nitrogen essential for (2)

Making amino acids and nucleic acids

What form of nitrogen is in the air

N2 (78% of the air)

What is nitrogen fixation

When nitrogen fixing bacteria combine atmospheric nitrogen (N2) with Hydrogen (H2) to produce ammonia (NH3)

Example of nitrogen fixing bacteria (2)

Rhizobium and Azotobacter

What type of relationship do nitrogen fixing bacteria and plants have

Symbiotic mutualistic relationship, where both organisms benefit

How do nitrogen fixing bacteria benefit from their relationship with plants

They gain carbohydrates produced by the plant during photosynthesis, which they can use as an energy source

How to plants gain from their relationship with nitrogen fixing bacteria

They gain amino acids from rhizobium, which are produced by fixing N2 into NH3 in the bacteria

What is nitrification

The process by which ammonium compounds in the soil are converted into nitrogen-containing molecules that can be used by plants

What type of reaction is nitrification

an oxidation reaction, that can only take place in well aerated soil (oxidation is loss of electrons)

Steps of nitrification (2)

1.nitrifying bacteria oxidise ammonium compounds into nitrites (NH3—> NO2-)
2. Nitrobacter oxidise nitrites into nitrates (NO2- —> NO3-)

Why does nitrification happen

Nitrate ions are highly soluble, and therefore the form in which nitrogen can enter most plants

What is denitrification

When denitrifying bacteria convert nitrates in the soil back into nitrogen gas in the absence of oxygen

What type of reaction is denitrification

Anaerobic reduction reaction

Why does denitrification occur

When O2 is limited, the soil bacteria use the nitrates as a source of energy for respiration, and therefore nitrogen gas is released

What is ammonification

The process by which decomposers convert nitrogen-containing molecules in dead organisms into ammonium compounds

What is the nitrogen cycle

the movement of nitrogen through the biosphere,the soil,the animal.

Why is the carbon cycle important

Carbon is an important element which makes up many different molecules in our environment and bodies (carbohydrates, fats and proteins). The amount of carbon on the Earth is fixed so it must be recycled.

Why do cardio dioxide levels fluctuate throughout the day (2)

-during the day, the photosynthesis can occur, so CO2 is removed from the atmosphere
-respiration is carried out all day so a relative stale volume of CO2 constantly enters the air

Why have CO2 levels risen so rapidly? (2)

-combustion of fossil fuels= has released CO2 back into the atmosphere from the carbon that had been trapped under the earths surface
-deforestation= has removed large quantities of photosynthetic biomass from earth, so less CO2 is removed from the atmosphere (sometimes forests are burned too which releases CO2)

Why is increased atmospheric levels of CO2 bad

It traps more thermal energy in the atmosphere, which raises temperature of the sea water, so less CO2 is absorbed into water, causing a positive feedback increase of CO2