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This lesson explains how genetic switches function and their role in the process of evolution through the use of clips from the HHMI DVD, Evolution: Constant Change and Common Threads, and the construction of a model. This activity can be done as a demonstration, a student inquiry activity, or a combination of the two.
Howard Hughes Medical Institute
Two 45-minute blocks
Occasionally, this lesson uses active/intentional language to describe evolutionary processes. Instructors should be sure to clarify the process as undirected and use this as a teachable opportunity. Also, instructors who want students to access video clips on their own directly may want to rewrite these links in the student materials so that they are in order as presented in the activity and link directly to the appropriate clip.
Correspondence to the Next Generation Science Standards is indicated in parentheses after each relevant concept. See our conceptual framework for details.
- Evolution results from natural selection acting upon genetic variation within a population.
- Natural selection and genetic drift act on the variation that exists in a population.
- Natural selection acts on phenotype as an expression of genotype.
- New heritable traits can result from mutations.
- Inherited characteristics affect the likelihood of an organism's survival and reproduction.
- 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.
- Complex traits can arise through the cooption of another trait.
- Speciation requires reproductive isolation.
- Reproductive isolation can occur through mechanisms that prevent fertilization from occurring.