Cretaceous-Paleogene Extinction Event

Definition

The Cretaceous-Paleogene extinction event, which occurred approximately 66 million years ago, marks a significant boundary in Earth's history when a catastrophic event led to the extinction of about 75% of all species, including the non-avian dinosaurs. This event is crucial in understanding evolutionary theory as it exemplifies how sudden changes in the environment can drive evolutionary adaptations and the eventual emergence of new species in the aftermath.

5 Must Know Facts For Your Next Test

1. The Cretaceous-Paleogene extinction event is widely believed to have been triggered by a 10-kilometer-wide asteroid impacting what is now the Yucatán Peninsula in Mexico.
2. This event not only wiped out non-avian dinosaurs but also affected marine reptiles, many bird species, and numerous plant species, drastically reshaping ecosystems.
3. The aftermath of the extinction event led to significant evolutionary opportunities for mammals and eventually paved the way for their dominance in the subsequent Cenozoic era.
4. Evidence for this extinction event includes a layer of clay rich in iridium, which is rare on Earth's surface but abundant in asteroids, marking the boundary between the Cretaceous and Paleogene periods.
5. The event underscores the principles of natural selection and evolution, showing how catastrophic environmental shifts can lead to rapid changes in species composition and evolution.

Review Questions

• How did the Cretaceous-Paleogene extinction event influence the evolutionary trajectory of mammals?
  • The Cretaceous-Paleogene extinction event opened up ecological niches that had been dominated by dinosaurs. With the sudden disappearance of large reptiles, mammals began to diversify and adapt to new environments. This evolutionary shift allowed mammals to evolve into larger forms and fill roles that were previously occupied by dinosaurs, leading to their eventual dominance in many ecosystems.
• Discuss the significance of the Impact Hypothesis in understanding the Cretaceous-Paleogene extinction event and its consequences for Earth's biodiversity.
  • The Impact Hypothesis posits that a massive asteroid impact was a primary cause of the Cretaceous-Paleogene extinction event. This theory has significant implications for understanding how sudden environmental changes can drastically affect biodiversity. The resulting climate shifts, fires, and tsunamis would have created hostile conditions for many species, leading to widespread extinctions and ultimately reshaping life on Earth.
• Evaluate how the Cretaceous-Paleogene extinction event serves as a case study for modern conservation efforts and our understanding of ecological resilience.
  • The Cretaceous-Paleogene extinction event demonstrates how ecosystems can respond to drastic changes through both extinctions and adaptations. Modern conservation efforts can learn from this historical event by recognizing that preserving biodiversity enhances ecological resilience against future environmental changes. Understanding past mass extinctions helps inform strategies for protecting vulnerable species today as they face threats like climate change and habitat destruction, emphasizing the need for proactive measures in conservation.

Related terms

Impact Hypothesis: The theory that suggests a massive asteroid impact caused the environmental changes leading to the mass extinction at the end of the Cretaceous period.

Iridium Layer: A geological signature found in sediment layers around the world, indicative of an asteroid impact and often associated with the Cretaceous-Paleogene boundary.

Mass Extinction: A rapid decrease in biodiversity on Earth, characterized by the extinction of a large number of species in a relatively short period.