1. The Evolution of Populations
Modern Synthesis Theory

2. Important Terms…
Microevolution: Change on a small scale (changes to a population gene pool from generation to generation)

3. Population: Local group of individuals that can breed & produce viable offspring
Gene Pool: The genes in a population (all alleles/traits)
Darwin’s theories were based on natural selection (but he didn’t know ANYTHING about genetics yet!!)

4. Modern Synthesis Theory
Based on Darwin’s ideas of natural selection AND Mendel’s ideas about heritability
Population genetics studies how populations change genetically over time
Modern Synthesis used ideas from many scientific areas to generate a complete view of evolutionary theory

5. How can populations change genetically??
Natural Selection- individuals who are better suited to their environment will survive to reproduce (higher fitness)
Genetic Drift- Chance events that change a gene pool (usually in small populations)

6. Bottleneck- Sudden change (ex
Bottleneck- Sudden change (ex. Fire/flood) dramatically reduces population size (by chance, certain alleles survive!)

7. Founder Effect-Some individuals (by chance) become isolated from larger population (Ex. Darwin’s finches; island colonies)
Gene Flow- Introduction of new alleles from immigrant population; can amalgamate different populations… look at humans as an example!
Think how you can create a simple diagram to illustrate genetic drift vs gene flow & add this to your notes.

8. How does Natural Selection Work??
Organisms with adaptive advantage over others
Increases the fitness of organisms
Fitness: the ability to survive to reproduce
Fitness is relative to the environment which a population lives in… this can change quickly or slowly over time, putting pressure on a population to change too!

9. Modes of Selection

10. Directional
Favours traits at ONE extreme

11. Stabilizing
Extremes are diminished; intermediate traits are seen

12. Disruptive
Both extremes (almost opposites) are favoured as traits

13. Sexual Selection
Animals (usually the females), may be preferential towards specific traits in males
These males mated with more frequently, passing favoured trait onto male offspring
Ex. Colourful plumage in male birds

14. In intrasexual selection, stronger more aggressive males are typically more successful reproductively