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.

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

Cheetahs today have incredibly low genetic diversity. Scientists believe this is due to a past event where only a few individuals survived, possibly due to climate change or overhunting.

In a Neotropical rainforest, a rare pollinator species declined due to climate change. Orchids that could attract alternative pollinators began to reproduce more, shifting flower shapes over generations.

On lava flows in the southwestern U.S., dark-colored rock pocket mice became more common than light-colored ones due to camouflage and predator pressure.

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

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.

Elephant seals were hunted nearly to extinction in the 1800s. All current northern elephant seals descend from about 20 individuals, and now they have very little genetic variation.

In Central America, forest fragmentation drastically reduced glass frog populations in some regions. These small, isolated populations now show less genetic diversity than others.

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.

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

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