One of the most important messages we can convey to our students is evolutionary theory’s role as an organizing principle across all of biology. To effectively communicate and reinforce this message, you can integrate evolution throughout your biology teaching, rather than isolating it as a discrete unit at the beginning or end of the semester. One approach would be to introduce basic evolutionary concepts at the beginning of the school year and then to refer back to these concepts in other units throughout the semester, so that students come away with the understanding that evolution helps explain phenomena in areas as diverse as respiration, photosynthesis, ecology, and human physiology. In addition, students at the high school level are ready to begin to explore the many applications of evolutionary theory in addressing practical problems in medicine, conservation, and agriculture. These topics should also be integrated throughout the semester.

The evolutionary concepts that are most important at this level are the four essential components of natural selection — an important mechanism of evolution:

• Variation: All life forms vary genetically within a population.
• Inheritance: Genetic traits are inherited from parents and are passed on to offspring.
• Selection: Organisms with traits that are favorable to their survival and reproduction are more likely to pass on their genes to the next generation.
• Time: Evolutionary change can happen in a few generations, but major change, such as speciation, often takes many thousands of generations.

By the end of twelfth grade, students should understand all the components of natural selection described above, as well as how these components work together, resulting in evolutionary change. At this level, students are also prepared to understand how small changes in populations caused by natural selection can accumulate into macroevolutionary change over geological timescales.

In grades 9-12, students should continue to be engaged in activities that reinforce the nature and process of science. This will help them differentiate between science and non-science, recognize the validity of evolution as science, and appreciate the explanatory power of evolutionary theory. To find resources for teaching these topics, visit the grades 9-12 teachers’ lounge on our sister site, Understanding Science.