Summary
Natural and artificial selection are processes that influence the traits of organisms over generations. Natural Selection — the process where organisms with favorable traits are more likely to survive and reproduce.
Example: Brown-furred rabbits surviving better than white-furred rabbits due to camouflage.
Artificial Selection — the intentional breeding of organisms by humans to produce desired traits.
Example: Breeding dairy cows for higher milk production.
Stabilising Selection — selection that maintains allele frequencies by favoring average phenotypes.
Example: Human birth weights being stabilized around an average.
Directional Selection — selection that causes allele frequencies to shift in one direction.
Example: A new advantageous allele increasing in frequency.
Disruptive Selection — selection that favors extreme phenotypes over intermediate ones.
Example: Polymorphism in a variable environment.
Genetic Drift — random changes in allele frequencies, especially in small populations.
Example: A small isolated group experiencing significant allele frequency changes.
Founder Effect — reduced genetic diversity when a population descends from a small number of ancestors.
Example: A new population started by a few individuals.
Genetic Bottleneck — a sharp reduction in population size affecting genetic diversity.
Example: A natural disaster drastically reducing population size.
Antibiotic Resistance — bacteria evolving to survive antibiotic treatments.
Example: MRSA bacteria resistant to multiple antibiotics.
Hardy-Weinberg Principle — a model describing allele frequencies in a non-evolving population.
Example: Predicting allele frequencies under certain conditions.
Exam Tips
Key Definitions to Remember
- Natural Selection
- Artificial Selection
- Stabilising Selection
- Directional Selection
- Disruptive Selection
- Genetic Drift
- Founder Effect
- Genetic Bottleneck
- Antibiotic Resistance
- Hardy-Weinberg Principle
Common Confusions
- Mixing up natural and artificial selection
- Confusing genetic drift with natural selection
- Misunderstanding the conditions for Hardy-Weinberg equilibrium
Typical Exam Questions
- What is not a feature of natural selection? Selection by humans
- Under Hardy-Weinberg equilibrium, what leads to steady allelic frequencies? Random mating
- How does antibiotic resistance develop in bacteria? Through random mutations and selection pressures
What Examiners Usually Test
- Understanding of different types of selection
- Ability to explain changes in allele frequencies
- Application of the Hardy-Weinberg principle
- Examples of natural and artificial selection in real-world scenarios
