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Ecology Index

Ecology : Introduction
Ecological Succession: Lake - Woodland Transition
Populations and Sampling
Modelling Population Growth
Biodiversity and conservation
What can be done to stop the loss of biodiversity?
Conservation Alternatives
The Carbon Cycle
The Nitrogen Cycle Flow Chart
The Nitrogen Cycle
Eutrophication
Methanogens and Biogas

Topic Chapters Index

 

The Grey Squirrel

Grey Squirrel

The Red Squirrel

Red Squirrel

© Maps prepared by the Biological Records Centre, CEH Monks Wood, from records collated by the Mammal Society and others mainly between 1965 and 1993, also including earlier, published records and a few additions up to 1997. The maps were drawn using Dr Alan Morton's DMAP software.

ECOLOGY

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The competitive exclusion principle

G.F. Gause 1934: If two species, with the same niche, coexist in the same ecosystem, then one will be excluded from the community due to intense competition.

The niche of a species consists of its role in the ecosystem (herbivore, carnivore, producer etc), its tolerance limits (e.g. soil pH, humidity) and requirements for shelter, nesting sites etc etc, all varying through time.

In mathematical terms this can be represented by an n-dimensional hypervolume!

To keep things simple the niche can be represented by a two-dimensional shape.

CEPI

CEPII

CEPIII

 

Example: Squirrels in Britain

The Red Squirrel (Sciurus vulgaris) is native to Britain but its population has declined due to competitive exclusion, disease and the disappearance of hazel coppices and mature conifer forests in lowland Britain.

The Grey Squirrel (Sciurus carolinensis) was introduced to Britain in about 30 sites between 1876 and 1929. It has easily adapted to parks and gardens replacing the red squirrel.

Today's distribution is shown by the maps to the left.

 

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