23.3 recycling within ecosystems

decomposition

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

decomposer

an organism that feeds on and breaks down dead plant or animal matter, thus turning organic compounds intoo inorganic ones

detrivores

another class of organism involved in decomposition - they help to speed up the decay process by feeding on dedtritus - dead and decaying matter

what do nitrogen fixing bacteria do

combine atmospheric nitrogen with hydrogen to produce ammonia

examples of nitrogen fixing bacteria

azotobacter - free living soil bacterium

rhizobium - living inside of root nodules. These are growths on the roots of leguminous plants and they have a symbiotic mutualistic relationship where both organisms benefit. The plant gains amino acids which are produced form fixing nitrogen in the air. the bacteria gain carbohydrates produced by the plant during photosynthesis, which they use as an energy source

what happens during nitrification + what conditions need to be met for nitrification to take place

• needs to take place in aerated soil

• nitrifying bacteria (such as nitrosomonas) oxidise ammonium compounds into nitrites

• nitrobacter (another genus of nitrifying bacteria) oxidise nitrites into nitrates

• nitrate ions are highly soluble and are therefore the form in which most nitrogen enters a plant

denitrification

in the absence of oxygen, for example, in waterlogged soils, denitrifying bacteria bacteria converts nitrates in the soil back to nitrogen gas

only happens under anaerobic conditions. The bacteria use the nitrates as a source of energy for respiration and nitrogen gas is released

ammonification

the process where decomposers convert nitrogen-containing molecules in dead organisms into ammonium compounds

fluctuations in atmospheric carbon dioxide during the day

photosynthesis only takes place in light therefore during the day photosynthesis removes carbon dioxide form the air. respiration is carried out constantly throughout the day and night.

seasonal fluctuations in carbon dioxide levels

carbon dioxide levels are lower on a summers day than a winters day as photosynthesis levels are higher

why have carbon dioxide levels in the atmosphere increased over the recent years

• the combustion of fossil fuels - which has released carbon dioxide back into the atmosphere from carbon which has previously been trapped for millions of years below the earths surface

• deforestation - which has removed significant quantities of photosynthesising biomass from earth. As a result, less carbon dioxide is removed from the atmosphere. Cleared forests are often burn which releases more carbon dioxide into the atmosphere

positive feedback loop of carbon dioxide being dissolved in the ocean

the amount of co2 dissolved in the seas is dependant on the temperature of the water( the higher the temperature, the less gas is dissolved) therefore global warming creates a positive feedback loop

how can variation in the earths carbon dioxide atmospheric levels over time be measured

samples are taken from deep within a glacier. When the ice formed, air bubbles were trapped within the ice - these bubbles reflect the composition of the atmosphere as that time