Factors Affecting the Evolution of a Species (OCR A-Level Biology A): Flashcards
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Selection pressures
Selection pressures
Factors giving certain individuals greater survival chance
Carrying capacity
Carrying capacity
Max population size a habitat can sustainably support
Stabilising selection effect
Stabilising selection effect
Removes extreme phenotypes, preserves characteristics
Example of stabilising selection
Example of stabilising selection
Human birth weight - extremes have higher mortality
Directional selection effect
Directional selection effect
Favours one extreme, population changes over time
Finch beak depth change 1976 to 1978
Finch beak depth change 1976 to 1978
9.4 mm to 10.2 mm (due to drought)
Genetic drift
Genetic drift
Random changes in allele frequency independent of selection
Genetic drift greatest impact location
Genetic drift greatest impact location
Small populations
Genetic bottleneck
Genetic bottleneck
Sharp population reduction causing reduced genetic diversity
Founder effect
Founder effect
Small population colonises new area, limited genetic diversity