Scientists generally agree that the Cretaceous-Paleogene mass extinction was caused by an asteroid impact. Which factor most likely explains the success and diversification of mammals and birds after that event?

After the impact, many ecosystems collapsed and conditions became harsh, but mammals and birds had traits that helped some survive and later diversify. Warm-bloodedness, hair or feathers, and relatively rapid reproduction could aid survival and recovery in changing environments. Depending on only a few plants would make food shortages more dangerous, not less, and tsunamis did not create lasting habitats that explain their success.

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