1. Natural Selection Acts On Phenotype
Natural selection acts on phenotypic variations in populations.

2. Environments change and act as selective mechanism on populations.

3. The environment does not directly cause changes in DNA, but acts upon phenotypes that occur through random changes in DNA

4. Example: Flowering time in relation to global climate change

5. Crop production is sensitive to climate change; temperature has a large impact on the rate of plant development.

6. Warmer temperatures will mean reduced crop yields.

7. “Earlier crop flowering and maturity have been observed and documented in recent decades, and these are often associated with warmer (spring) temperatures.”
―Climate change and the flowering time of annual crops by P.Q. Craufurd and T.R. Wheeler, Journal of Experimental Botany, 2009.

8. Example: Peppered moth

9. The light phenotype was favored before the Industrial Revolution
The light phenotype was favored before the Industrial Revolution. The color blended with the tree bark.

10. After the Industrial Revolution, mostly dark colored moths were seen
After the Industrial Revolution, mostly dark colored moths were seen. They had an advantage on dark tree bark.

12. Phenotypic variations are not directed by the environment but occur through random changes in the DNA and through new gene combinations.

13. Changes in genetic information may be silent (with no observable phenotypic effects) or result in a new phenotype.

14. Some phenotypic variations significantly increase or decrease fitness of the organism and the population.

15. Example: Sickle cell anemia and Heterozygote Advantage

16. Sickle cell gene allele frequency

17. Sickle cell disease is caused by a single base substitution mutation
Sickle cell disease is caused by a single base substitution mutation. It is maintained in the population in a state of balanced polymorphism because of the protective effect against severe forms of malaria conferred by the heterozygous states.

18. Example: The Peppered moth

19. Example: DDT resistance in insects

20. Humans impact variation in other species.

21. Example: Artificial selection

22. Example: Loss of genetic diversity within a crop species

23. Example: Overuse of antibiotics leading to increase in antibiotic resistant bacteria.

24. Biggest problem: overuse and improper use of antibiotics, especially in livestock.

26. Directional Selection is most common when an environment changes
Directional Selection is most common when an environment changes. One phenotype favored over another.

27. Example: the peppered moth

28. Stabilizing selection maintains the status quo by favoring the mean phenotype.

29. Example: human birth weight

30. Distruptive selection occurs when the extreme phenotypes are favored
Distruptive selection occurs when the extreme phenotypes are favored. May lead to speciation.

31. Example: Wood Frog and Leopard Frog
Breeds in early April
Leopard Frog
Breeds in mid-April

32. geographic variation – difference in variation between population subgroups in different areas

33. A cline is a graded change in a trait along a geographic axis.