Populations in ecosystems GapFill

Ecosystems consist of a  speciescommunityhabitatpopulation of different organisms and all the abiotic factors in the environment. Each organism has its own  nichehabitatbiomebiosystem, which is where it usually lives, and dominant species tend to do best here due to the  competitive exclusionprimary successiongenotype-phenotypesurvival of the fittest principle.  Interspecific competitionPredationSpeciationMutation 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  belt transectsframe quadratspoint countsgene pools placed on the ground, with their  magnificationsfrequenciesoverall sizespositions generated using coordinates. Where it is easy to do so,  densityfractionabundancetally, or the number of individuals of a species, can be counted at each location. Alternatively, the  percentageabundancedistributionfrequency of different species can be estimated by calculating the proportion of locations at which a certain species was seen. For a species which moves around more, a  count-recounttag-returncount-release-recountmark-release-recapture method can be adopted.

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 producera foundera buildera pioneer species. If an area of land which had previously supported life is disturbed in some way, e.g. by fire or grazing, and succession begins again (not from scratch), this is referred to as  recolonisationprimary progressionsecondary successionprimary continuation.  ConservationPreservationMicropropagationEco-development often involves managing succession in this way.