Advanced Higher Biology - Unit Two - Changes to Ecosytems (i) Changes in complexity
What is a pioneer species?
The species which colonise an area and are able to tolerate the harsh enviornmental conditions present
What is a climax community?
The mature or stabilised stage in a succession, where the dominant species are completely adapted to environmental conditions
What is autogenic succession?
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
Name and describe the two types of autogenic succession
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
Which type of autogenic succession would take longer and why?
Primary autogenic succession as soil must be formed
What is allogenic succession?
Allogenic succession is when a climax or mature community is disturbed by environmental factors unrelated to the organisms present eg hurricanes, forest fires, volcano
What is degredative succession?
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
During autogenic succession what happens to the speices diversity, habitat variety, productivity, complexity of food webs, stability and productivity?
They all increase
Loss of complexity in ecosystems can be brought about by...?