Population
A group of interbreeding individuals of the same species occupying the same geographic area.
Formula
Population change = (Births + Immigration) − (Deaths + Emigration)
Real World
The UK's red squirrel population has declined sharply since grey squirrels were introduced in the 1870s, with remaining populations now isolated in areas like Formby and the Scottish Highlands.
Exam Focus
When describing population change, always reference all four factors: births, deaths, immigration, emigration.
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