Changes to Ecosytems (i) Changes in complexity

The species which colonise an area and are able to tolerate the harsh enviornmental conditions present

The mature or stabilised stage in a succession, where the dominant species are completely adapted to environmental conditions

Autogenic succession is the changes in environmental conditions which leads to changes in species composition in an ecosystem caused by the biological processes of the organisms themselves

• Primary succession - the colonisation of land which has not previously been inhabited and no soil exists
• Secondary succession - when an existing ecosystem (with soil already present) has been damaged or destroyed (eg by forest fire) and it becomes recolonised by other pioneer species

Primary autogenic succession as soil must be formed

Allogenic succession is when a climax or mature community is disturbed by environmental factors unrelated to the organisms present eg hurricanes, forest fires, volcano

• Degredative succession is associated with the process of decomposition.  This is when a fixed amount of energy/nutrients (eg a dead plant) is released back into the ecosystem by decomposers such as bateria and fungi
• Degradative succession is also known as heterotrophic succession since no autotrophs are involved in the process

They all increase

• Monoculture
• Eutrophication
• Toxic pollution
• Habitat destruction