Explain how humans use selective breeding to increase the frequency of desired traits over generations, and compare the process to natural selection.
Humans have shaped other species for thousands of years through selective breeding (also called artificial selection): choosing individuals with a desired trait and breeding them together, generation after generation, until that trait becomes far more common, or more extreme, than it was in the original population. Nearly all dog breeds descend from wolves, shaped over thousands of years of selecting for traits like size, temperament, and herding ability. Corn was bred over thousands of years from a wild grass called teosinte, which had tiny ears just a few centimeters long, into today's large-eared corn.
One especially clear example is wild mustard (Brassica oleracea), a single wild plant species that farmers reshaped into several completely different-looking vegetables just by selecting for different parts of the plant: choosing plants with larger flower buds, generation after generation, eventually produced broccoli and cauliflower; selecting for larger terminal buds produced cabbage; selecting for thicker stems produced kohlrabi; selecting for larger leaves produced kale. Every one of these vegetables came from the same ancestral species, reshaped by which individual plants humans chose to breed.
Mastery looks like: They can describe how selective breeding changes a population over generations and explain why it typically proceeds faster than natural selection.
Common stumbles: Thinking a desired trait appears after just one round of breeding; confusing selective breeding (human-directed) with natural selection (environment-driven), covered next.