Rate of decay:- Temperature - a warm temperature makes things decay faster because it speeds up respiration in micro-organisms Amount of water - things decay faster when they're moist because micro-organisms need water Amount of oxygen (air) - decay is faster when there's oxygen available. The micro-organisms can respire aerobically, providing more energy.
Things decay because because of micro-organisms. Nearly all of decomposition is done by micro-organisms like soil bacteria and fungi.
Detritivores and saphrophytes:- Detritivores feed on dead and decaying material. Examples of detritivores include earthworms, maggots and woodlice. As these detritivores feed on the decaying material, they break it up into smaller bits.This gives a bigger surface area for smaller decomposers to work on and so speeds up decay. Saprophytes also feed on decaying material, but they do so by extracellular digestion - i.e. they feed by secreting digestive enzymes on to the material outside of their cells. The enzymes break down the material into smaller bits, which can then be absorbed by the saprophyte. Many saprophytes are fungi.
Food preservation method reduce the rate of decay:- Canning - this involves putting food in an airtight can which keeps decomposers out. Cooling - putting food in a fridge slows down decay because it slows the decomposers' reproduction rate Freezing - food lasts longer in the freezer than in the fridge because decomposers can't reproduce at all at such low temperatures. Drying - dried food lasts longer because decomposers need water to carry out cell reactions. Lots of fruits are preserved by drying them out, and sometimes meat is too. Adding salt/sugar - if there's a high concentration of salt or sugar around decomposers, they'll lose water by osmosis. This damages them and means they can't work properly. things like tuna and olives are often stored in brine (salt water). Adding vinegar - vinegar is acidic, and the acid kills the decomposers.