Organism Distribution Flashcards
Biotic factors: can interact with organisms in ways that abiotic factors can’t (3)
Potential food,
Competitors,
Partners.
Biotic factors: organisms and their products
Act as resources and conditions.
Bottom-up controls are
Limits on distribution because of resources.
Top-down controls are
Species being limited or excluded by a predator.
Eg the water vole and American mink.
Inter specific competition is the competition between species, occurs when
The abundance of two neighbouring species is limited by the same resource.
Competitive exclusion; two species compete for the same resource:
If species
The BMWP index is a score assigned for each invertebrate family in a sample, the
Individual scores are added together to produce an index value.
The BMWP index is based on the principle that freshwater invertebrates
Differ in their sensitivity to organic pollution; more sensitive = higher score to family.
Coexisting by niche separation:
Species may have different growths in different seasons,
Eg meadow foxtail and Yorkshire fog.
Coexisting by climatic variation:
In years that may be extremely dry or cold, a species better adapted to the habitat will be able to establish a place.
Eg buffalo grass is more dominant in wetter years, whilst Blue Grama is more dominant in drier years.
Coexisting by establishment opportunities:
Species with rapid growth and good seed dispersal have an opportunity to fill a gap in the existing vegetation.
Eg meadow grass has a high seed production and seeds can survive dormant in the soil for many years.
Fundamental niche:
The range of environments in which a given species could survive in the absence of competition from other species.
Realised niche:
Proportion of the fundamental niche occupied by a species when in competition with other species for limited resources.
