BRAINCAKESelection Pressure
A selection pressure is any environmental factor that affects the chance of an organism surviving and reproducing. Examples include predation, disease, competition for food, mates or light, and abiotic factors such as temperature or the presence of a toxin such as an antibiotic or pesticide.
Selection pressures act on phenotypes, but the effect is on alleles. Natural selection works like this:
1. There is variation in a population, caused by different alleles.
2. A selection pressure acts. Individuals with alleles that give an advantageous phenotype are more likely to survive.
3. These individuals reproduce and pass the advantageous alleles on to their offspring.
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More in Gene Pools
- Mutations
- Non-Random Mating
- Different Sized Populations
- Isolation
- Population Bottlenecks
- The Founder Effect
- Stabilising Selection
- Directional Selection
All 16 lessons in Gene Pools · All Edexcel A-level Biology topics