Directional & Stabilising Selection (AQA A-Level Biology): Flashcards
📚Flashcards
Practise the cards
10 cards from this deck
ShowHide
Practise the cards
10 cards from this deck
Definition of selection
Definition of selection
Better-adapted organisms more likely survive & reproduce
Polygenes
Polygenes
Multiple genes that control one characteristic
Directional selection
Directional selection
Selection favoring one extreme of population distribution
Phenotype
Phenotype
Observable physical & biochemical traits
Effect of directional selection on mean
Effect of directional selection on mean
Shifts population mean towards favored extreme
Stabilising selection
Stabilising selection
Selection favoring average, selecting against extremes
Effect of stabilising selection on curve
Effect of stabilising selection on curve
Taller & narrower curve, same mean, reduced variation
Anatomical adaptation example
Anatomical adaptation example
Arctic fox: shorter ears, thicker fur
Physiological adaptation example
Physiological adaptation example
Kangaroo rat: concentrated urine for water conservation
Behavioural adaptation example
Behavioural adaptation example
Swallow: seasonal migration to avoid food shortage