Essential Knowledge 1.A.2

Natural selection acts on phenotypic variations in populations.

Environments change and act as selective mechanism on populations. Illustrative examples can include:

• Flowering time in relation to global climate change.
• Peppered moth.

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

Some phenotypic variations significantly increase or decrease fitness of the organism and the population. Illustrative examples can include:

• Sickle cell anemia
• Peppered moth
• DDT resistance in insects

Humans impact variation in other species. Illustrative examples can include:

• Artificial selection
• Loss of genetic diversity within a crop species
• Overuse of antibiotics

Students should be able to:

LO 1.4 Evaluate data-based evidence that describes evolutionary changes in the genetic makeup of a population over time.

LO 1.5 Connect evolutionary changes in a population over time to a change in the environment.