Overview: This 14-minute film describes the connection between the infectious parasitic disease malaria and the genetic disease sickle cell anemia - one of the best-understood examples of natural selection in humans. Author/Source: Howard Hughes Medical Institute Grade level: 9-12 Time: 15-30 minutes Teaching tips: HHMI provides a variety of teacher resources for use with this video: an in-depth film guide, student quiz, two worksheets and three student lessons. Concepts: There is a fit between organisms and their environments, though not always a perfect fit. Evolution results from selection acting upon genetic variation within a population. Mutations are random. Traits that confer an advantage may persist in the population and are called adaptations. Inherited characteristics affect the likelihood of an organism's survival and reproduction. Depending on environmental conditions, inherited characteristics may be advantageous, neutral, or detrimental. Natural selection acts on the variation that exists in a population. Natural selection acts on phenotype as an expression of genotype. Organisms cannot intentionally produce adaptive mutations in response to environmental influences. Populations, not individuals, evolve. Over time, the proportion of individuals with advantageous characteristics may increase (and the proportion with disadvantageous characteristics may decrease) due to their likelihood of surviving and reproducing. There is variation within a population. Natural selection is dependent on environmental conditions. Environmental changes may provide opportunities that can influence natural selection. Some traits of organisms are not adaptive.

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