1. NATURAL SELECTION

2. What is the source of variation? How are subtle differences passed from generation to generation? These questions that puzzled Darwin have been answered by the understanding of genetics and mutations

3. Mutations Mutations provide a continuous supply of new genetic variations Natural selection leads to variety of outcomes when this genetic variation occurs within a competitive populations

4. Patterns of Selection Sickle Cell Anaemia – provides a useful example of selection in action Individuals that are homozygous for the condition suffer debilitation effects and are selected against

5. Those that are heterozygous have a resistance to malaria and are selected for in areas where malaria is prevalent The sickle-cell allele is only common where it provides an overall advantage to the individual in resistance to malaria

6. Basic Pattern Harmful mutations are frequent but selected against Beneficial mutations are rare but selected for so they accumulate over time

7. Types of Selection Many factors influence how selection can operate on individual phenotypes: 1. Stabilizing selection Environment selects the most common phenotype Eg. Bill length in hummingbirds fits food source

8. 2. Directional selection Environment favours individuals with more extreme variations of a trait Eg. Hummingbird population moves to new habitat with longer flowers

9. 3. Disruptive Selection Favours individuals with opposite extreme traits over those with intermediate variations Eg. Hummingbird population in a habitat with both short and long flowers, birds with longer and shorter bills will be more successful

10. 4. Sexual selection Favours the selection of any trait that influences the mating success of the individual (usually male) Results in sexual dimorphism (striking differences between males and females)

11. Read pgs 561, 562 and answer # 1-4 pg 562 Selection and Antibiotic Resistance

12. Cumulative Selection Evolution of a complex structure such as the eye is a cumulative process Rare, beneficial mutations may be separated by vast amounts of time Natural selection favours them and the adaptations they produce accumulate one by one

13. Cumulative selection is the accumulation of many small evolutionary changes over long periods of time and many generations, resulting in a significant new adaptation relative to the ancestral species

14. Evolution of Insect Pollination The interactions between flowers and the their pollinators are fascinating Many devious mutations in flowers lure insects to visit them with sugars (nectar), proteins (pollen), and floral oils and fragrances

15. Does Selection explain altruism? Altruistic behaviours increase the fitness of the recipient yet decrease the fitness of the giver This concerned Darwin Later Science addressed this and explained the behaviour as kin selection

16. Kin Selection explains that altruistic behaviours of an individual benefit closely related individuals, thus increasing the first individual’s fitness indirectly A warning call from a prairie dog draws predators to himself but likely saves members of his family, which ensures perpetuation of his shared genes