Ecosystems GapFill

Biomass is transferred to the next  food chainhabitattrophic levelniche when an organism is eaten by another, and the  abundanceproductivityefficiencyfeasibility of the transfer can be calculated using an equation. Nutrients in organisms are also recycled in ecosystems by  producerseukaryotesapex predatorsdecomposers, before being released into the soil. Nitrogen is important for synthesising proteins and nucleic acids, but most organisms cannot make use of gaseous nitrogen. Nitrogen fixation is the process by which mutualistic bacteria living in nodules on the roots of plants (called  AzotobacterRhizobiummyceliumFusarium) convert nitrogen gas to  proteinsDNAammoniaurea, and then to amino acids, gaining carbohydrates in return.

Three other processes are essential in cycling nitrogen:

Ecosystems consist of a community of different organisms and all the abiotic factors in the environment.  PredationInterspecific competitionMutationSpeciation can create cycles of rising and falling population numbers; as animal A consumes animal B, B's population size is reduced, but, in time, A's population size falls due to a reduced food supply, and B's population recovers.

The size of a non-motile population can often be estimated by random sampling using  frame quadratspoint countsbelt transectsgene pools placed on the ground, with their positions generated using coordinates. Where it is easy to do so,  tallyfractiondensityabundance, or the number of individuals of a species, can be counted at each location.

Different species are present or absent in an area over time as the landscape changes, and this is known as succession. When a barren, inhospitable area of land is first colonised, the species which does this is known as   a buildera foundera producera pioneer species. If a stable end-stage is reached naturally, often deciduous woodland in the UK, this is known as  an interspecific habitata combined nichea secondary successiona climax community.