First 425 words of the document:
Ecosystem A community of different species that are dependent on each other, and the
non-living environment, in a relatively self-contained area.
Population All the members of the same species living in a particular area at the same time.
In species which reproduce sexually there is interbreeding between males and
Community All the organisms of all the populations that live in a particular area at the same
Biotic factor The living environment that influence populations in a community e.g.
competition, predation, mutualism and disease.
Abiotic Factor The non-living environment, physical and chemical factors, that influence
populations in a community e.g. temperature, wind, soil depth.
Edaphic Any abiotic factor of the soil that influences the distribution/abundance of
factor plants, and therefore animals too e.g. texture, pH, temperature, O2 content.
Nitrogen A chemical element that s in many biological molecules like proteins and DNA. N2
makes up most of the atmosphere and is not very reactive so most organisms
cannot use it direct.
Nitrification The process in which ammonium ions are oxidised to nitrate ions by the bacteria
Nitrosomonas and Nitrobacter.
2NH3 + 3O2 2NO2 - + 2H+
2NO2- + O2 2NO 3-
Nitrogen The process in which nitrogen gas is changed into ammonium ions by nitrogen
fixing organism like Azotobacter and Rhizobium.
Denitrificatio The process in which nitrate ions are reduced by bacteria in anaerobic conditions
n to dinitrogen (N2).
NO3 - NO2 - N2
Succession The change in communities that occurs when new land becomes available to
colonise (primary) or when the vegetation is cleared (secondary).
Primary The colonisation of land that has never been colonised before followed by the
succession progression of changes until a climax community is reached.
Seral stage One of the communities during a succession
Pioneer Pioneer species are hardy species which are the first to colonise previously
species disrupted or damaged ecosystems, beginning a chain of ecological succession.
Climax The community that is the final stage of a natural succession.
Deflected A succession that does not progress to the natural climax community; factors
succession that cause this are grazing, mowing and fires.
Plagioclimax The community that becomes established when deflected succession occurs.
Chalk grassland is an example of a plagioclimax.