There are 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 eighth grade, students should understand all the components of natural selection described above. They should also understand how the different components of natural selection work together, resulting evolutionary change.

In grades 6-8, 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 6-8 teaching guide on our sister site, Understanding Science.