In this lesson, we review the following topics: “The Theory of Evolution by Natural Selection,” “Variation and Sexual Reproduction,” “Sexual selection,” and “Adaptation and Fitness.” Each topic comprises a video lecture reviewing the topic and the corresponding text and illustrations. You can both watch and read the topic. There is a knowledge review for each lesson which you must complete to advance to the next lesson.

• The theory of evolution by natural selection is very simple. All it requires is variation, heredity, and differential fitness. Natural selection handles the rest, and evolution necessarily occurs.
• A sexually reproducing population can respond quicker to environmental changes than parthenogenesis allows.
• Fruit fly females, Drosophila, only accept to be mated by males able to perform an elaborate courtship dance to perfection. Studies show better sperm quality among good male dancers than poorer dancers.
• Without variation, there would be no natural selection because there would be nothing to choose. However, there would be no evolution without heredity because chosen traits would not affect subsequent generations.