Cretaceous-Paleogene extinction

Definition

The Cretaceous-Paleogene extinction event was a major biological event that occurred approximately 66 million years ago, leading to the mass extinction of about 75% of Earth's species, including the dinosaurs. This extinction is significant as it marks the end of the Mesozoic Era and sets the stage for the rise of mammals and birds in the subsequent Paleogene period.

5 Must Know Facts For Your Next Test

1. The Cretaceous-Paleogene extinction is one of the five major mass extinction events in Earth's history and resulted in significant loss of biodiversity.
2. It is widely accepted that an asteroid impact, along with extensive volcanic activity (Deccan Traps), contributed to the dramatic environmental changes that caused this extinction.
3. The loss of large terrestrial reptiles, including dinosaurs, allowed mammals to diversify and occupy ecological niches left vacant by extinct species.
4. The extinction event led to drastic changes in climate and ecosystems, which took millions of years to stabilize.
5. Fossil evidence indicates that small mammals survived the extinction, leading to the eventual rise of mammals as the dominant terrestrial vertebrates.

Review Questions

• How did the Cretaceous-Paleogene extinction event influence the evolutionary trajectory of mammals?
  • The Cretaceous-Paleogene extinction event drastically altered ecosystems and eliminated dominant groups like dinosaurs. With their extinction, mammals were able to diversify and adapt to new ecological roles that were previously occupied by reptiles. This opened up various niches for mammals to exploit, leading to their evolution into a wide array of forms, ultimately allowing them to become the dominant terrestrial vertebrates in the succeeding Paleogene period.
• Evaluate the evidence supporting both asteroid impact and volcanic activity as causes of the Cretaceous-Paleogene extinction.
  • Evidence for the asteroid impact includes the discovery of the Chicxulub Crater and a global layer of iridium-rich sediment found at the Cretaceous-Paleogene boundary. In contrast, volcanic activity from the Deccan Traps released vast amounts of sulfur dioxide and carbon dioxide, which likely led to climatic changes such as acid rain and global cooling. Both hypotheses are supported by geological data, indicating that multiple factors likely contributed to this extinction event.
• Synthesize how understanding the Cretaceous-Paleogene extinction can inform current conservation efforts regarding biodiversity loss.
  • Understanding the Cretaceous-Paleogene extinction provides insights into how sudden environmental changes can lead to catastrophic biodiversity loss. It highlights the importance of monitoring climate change, habitat destruction, and species interactions to prevent similar events today. By learning from past extinctions, conservation strategies can be developed that focus on preserving ecosystems and mitigating human impact, ensuring a more resilient planet for current and future species.

Related terms

Chicxulub Crater: A large impact crater located on the Yucatan Peninsula in Mexico, believed to be the result of the asteroid impact that triggered the Cretaceous-Paleogene extinction.

Mass Extinction: A rapid and widespread decrease in biodiversity on Earth, often driven by catastrophic events such as asteroid impacts, volcanic eruptions, or climate change.

Iridium Layer: A layer of sediment rich in iridium found in the geological record, often associated with the Cretaceous-Paleogene boundary, indicating an extraterrestrial impact.