In a lizard population, those with longer legs can run faster and escape predators. Over time, long-legged lizards become more common.

Several genetic disorders (e.g., Tay-Sachs) are more common in Ashkenazi Jewish populations due to a small ancestral population and historical isolation.

Modern Icelanders are genetically very similar, with many traits traceable to original Viking settlers.

In regions with high malaria, individuals with one sickle cell allele are more likely to survive malaria. Over time, this trait became more common in those populations.

Five birds accidentally get trapped in a shipping container and are transported to a new continent. Their descendants look and behave differently than the original population.

Some bromeliads (Neotropical plants) colonize isolated tree islands in flooded forests. Each small population shows slightly different flower colors due to limited gene flow and random allele changes over time.

On one Galápagos island, droughts reduced soft-seed plants. Only finches with longer, stronger beaks could crack the tougher seeds, so that trait became more common in the next generation.

Hunters over-harvest a fish population, leaving just a few fish with rare striping patterns. Now, most of that species has stripes.

During El Niño events, food becomes scarce and smaller-bodied marine iguanas tend to survive better than larger ones, leading to a noticeable shift in body size in following generations.

Island Foxes on California’s Channel Islands have several islands that were colonized by small groups that migrated to them and have unique traits on each island

In certain areas of Costa Rica, hummingbirds have developed beak shapes that perfectly match the curvature of local Heliconia flowers. Birds with the best fit get the most nectar—and reproduce more.

In a desert, lizards that blend in with the sand survive more often. Over time, fewer bright green lizards are born.

On Pingelap, a small Pacific island, a typhoon reduced the population to about 20 people. One survivor carried a rare gene for color blindness, which is now unusually common in the population.