Extinction & Rapid Change
Explain how environmental change can outpace a species' ability to adapt through natural selection, leading to extinction, using historical and contemporary examples
What a learner can do afterwards
- Explains why extinction occurs when environmental change is faster than the rate of adaptation
- Gives a historical example (e.g. woolly mammoth, dodo) and a contemporary example of threatened extinction
- Distinguishes between background extinction rates and mass extinctions
- Explains how human activity (habitat loss, hunting, climate change) is driving current species loss
The lesson
Natural selection can help a species adapt to its environment, but only if the environment changes slowly enough. Adaptation happens over many generations, as small differences get passed down and useful traits become common. If the environment changes faster than a species can adapt through this process, the species can disappear completely. This is called extinction.
About 10,000 years ago, the last ice age ended. Earth's climate warmed quickly, and the grasslands woolly mammoths depended on shrank into forests and tundra. At the same time, human hunters spread across mammoth territory. Mammoths had survived earlier climate swings, but this combination of fast warming and hunting pressure happened too quickly for the species to adapt. The last woolly mammoths died out a few thousand years later.
Today, the vaquita porpoise, a small animal that lives only in one part of the Gulf of California, is critically endangered. Vaquitas often get trapped and drown in fishing nets set for other species. Fewer than 10 are thought to survive in the wild. Unlike the mammoth, this loss is happening within a single human lifetime, driven mainly by fishing practices rather than climate change.
Scientists separate two extinction rates. The background rate is the slow, steady loss of species that has always happened throughout Earth's history. A mass extinction is when a huge number of species disappear in a short span of time, usually because of a sudden, severe change like an asteroid impact or huge volcanic eruptions. Many scientists think today's rate is now closer to a mass extinction, but this time the main cause is human activity: habitat loss, hunting, and climate change.
Extinction happens when environmental change outpaces a species' ability to adapt, and today's human-driven changes are pushing species like the vaquita toward the same fate as the woolly mammoth.
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