Decomposers are organisms that break down dead organisms, faeces and other waste, releasing inorganic nutrients back into the environment. The main decomposers are bacteria and fungi.Decomposers are saprotrophs (saprobionts). They feed by extracellular digestion:
1. They secrete enzymes onto the dead organic matter.
2. The enzymes hydrolyse large molecules, such as proteins, cellulose and nucleic acids, into small soluble molecules.
3. The decomposer absorbs these small molecules and uses them in respiration and to build its own cells.As a result, carbon is released as carbon dioxide from their respiration, and nitrogen from proteins and nucleic acids is released as ammonium ions. These can then be taken up by plants again. Without decomposers, nutrients would stay locked up in dead matter and plants would soon run short of them.Detritivores, such as earthworms, woodlice and millipedes, help. They feed on dead material (detritus) and digest it internally, but they also break it into smaller pieces. This increases the surface area for decomposers to act on, speeding up decay.Factors affecting the rate of decomposition
• Temperature: warm conditions increase enzyme activity.
• Water: moist conditions are needed; decay is slow in dry places.
• Oxygen: most decomposers respire aerobically, so decay is slow in waterlogged soil.
This is why leaf litter builds up in cold or waterlogged places, such as peat bogs.
1. They secrete enzymes onto the dead organic matter.
2. The enzymes hydrolyse large molecules, such as proteins, cellulose and nucleic acids, into small soluble molecules.
3. The decomposer absorbs these small molecules and uses them in respiration and to build its own cells.As a result, carbon is released as carbon dioxide from their respiration, and nitrogen from proteins and nucleic acids is released as ammonium ions. These can then be taken up by plants again. Without decomposers, nutrients would stay locked up in dead matter and plants would soon run short of them.Detritivores, such as earthworms, woodlice and millipedes, help. They feed on dead material (detritus) and digest it internally, but they also break it into smaller pieces. This increases the surface area for decomposers to act on, speeding up decay.Factors affecting the rate of decomposition
• Temperature: warm conditions increase enzyme activity.
• Water: moist conditions are needed; decay is slow in dry places.
• Oxygen: most decomposers respire aerobically, so decay is slow in waterlogged soil.
This is why leaf litter builds up in cold or waterlogged places, such as peat bogs.