• [Evidence of evolution: Grades 6-8] An organism's features reflect its evolutionary history.
• [Evidence of evolution: Grades 6-8] There is a fit between the form of a trait and its function, though not always a perfect fit.
• [Evidence of evolution: Grades 6-8] Anatomical similarities of living things reflect common ancestry. (LS4.A)
• [Evidence of evolution: Grades 9-12] An organism's features reflect its evolutionary history.
• [Evidence of evolution: Grades 9-12] There is a fit between the form of a trait and its function, though not always a perfect fit.
• [Evidence of evolution: Grades 9-12] Anatomical similarities of living things reflect common ancestry. (LS4.A)
• [Evidence of evolution: Grades 13-16] An organism's features reflect its evolutionary history.
• [Evidence of evolution: Grades 13-16] There is a fit between organisms and their environments, though not always a perfect fit.
• [Evidence of evolution: Grades 13-16] Similarities among existing organisms (including morphological, developmental, and molecular similarities) reflect common ancestry and provide evidence for evolution.
• [Mechanisms of evolution: Grades 6-8] Traits that are advantageous often persist in a population. (LS4.B, LS4.C)
• [Mechanisms of evolution: Grades 9-12] Natural selection acts on the variation that exists in a population. (LS4.B, LS4.C)
• [Mechanisms of evolution: Grades 9-12] Traits that confer an advantage may persist in the population and are called adaptations. (LS4.B, LS4.C)
• [Mechanisms of evolution: Grades 13-16] Evolution results from natural selection acting upon genetic variation within a population.
• [Mechanisms of evolution: Grades 13-16] Traits that confer an advantage may persist in the population and are called adaptations.

• Disciplinary Core Idea LS4.A: Evidence of Common Ancestry and Diversity
• Disciplinary Core Idea LS4.B: Natural Selection
• Disciplinary Core Idea LS4.C: Adaptation

This article helps dispel the misconception that natural selection is all-powerful and produces perfectly adapted organisms. Classroom discussion (especially regarding the key questions at the beginning of the article) would enhance student learning on these topics.

Additional teaching tips for 9-12:
More advanced students may wish to follow the side trips for more information.

Additional teaching tips for 13-16:
Use this resource to relate evolutionary concepts to the topics of animals and animal behavior (or get more suggestions for incorporating evolution throughout your biology syllabus). More advanced students may wish to follow the side trips for more information. Classroom discussion (especially regarding the key questions at the beginning of the article) would enhance student learning on these topics.

• Adaptation