BRAINCAKEDirectional Selection
For many characteristics, such as body mass or height, a population shows a range of values that forms a roughly normal distribution around a mean. Natural selection can change this distribution in different ways.
Directional selection happens when individuals at one extreme of the range have a selective advantage. This usually occurs when the environment changes, so the previous mean is no longer the best value.
The steps are:
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Key terms in this lesson
- selection pressure
- An environmental factor that affects the chance of survival and reproduction of organisms with a particular allele or characteristic.
More in Natural Selection
- Natural Selection
- Natural Selection in Oysters
- Natural Selection in Moths
- Reproductive Success
- Antibiotics
- Antibiotic Resistance
- Preventing Antibiotic Resistance
- Speciation
All 29 lessons in Natural Selection · All Edexcel AS-level Biology topics