Study Notes
Gene pools and speciation involve understanding the genetic diversity within populations and how new species arise. Gene pool — the sum total of all alleles in a sexually reproducing population. Example: A large gene pool indicates high genetic diversity. Allele frequencies — the proportion of a particular allele within a population. Example: Allele frequencies change over time due to evolution. Reproductive isolation — occurs when populations are separated by temporal, behavioral, or geographic barriers. Example: Geographic isolation can lead to speciation. Speciation — the formation of new and distinct species in the course of evolution. Example: Speciation can be gradual or abrupt. Punctuated equilibrium — long periods of stability interrupted by rapid evolutionary changes. Example: Rapid speciation due to geographic isolation. Stabilising selection — favors intermediate phenotypes over extremes. Example: Human birth weights. Directional selection — favors one extreme phenotype over others. Example: Antibiotic resistance in bacteria. Disruptive selection — favors extreme phenotypes over intermediates. Example: Black or white moths in contrasting environments.
Exam Tips
Key Definitions to Remember
- Gene pool
- Allele frequencies
- Reproductive isolation
- Speciation
- Punctuated equilibrium
- Stabilising selection
- Directional selection
- Disruptive selection
Common Confusions
- Confusing gene pool with allele frequency
- Misunderstanding the types of reproductive isolation
Typical Exam Questions
- What is a gene pool? The sum total of all alleles in a population.
- How does reproductive isolation lead to speciation? By preventing gene flow between populations.
- What is an example of directional selection? Development of antibiotic resistance in bacteria.
What Examiners Usually Test
- Understanding of how allele frequencies change over time
- Ability to identify examples of different types of selection
- Explanation of how reproductive isolation can lead to speciation