Cretaceous-Paleogene extinction

Definition

The Cretaceous-Paleogene extinction was a major event that occurred approximately 66 million years ago, marking the end of the Cretaceous period and leading to the extinction of around 75% of all species on Earth, including the non-avian dinosaurs. This event is significant as it reshaped the course of evolution and led to the dominance of mammals in subsequent eras.

5 Must Know Facts For Your Next Test

1. The Cretaceous-Paleogene extinction event is often linked to a combination of catastrophic events, including an asteroid impact and extensive volcanic activity, particularly from the Deccan Traps in present-day India.
2. Evidence for the asteroid impact includes shocked quartz and spherules found in boundary layers around the world, which are consistent with high-energy impacts.
3. The extinction event led to significant changes in Earth's ecosystems, allowing mammals to evolve and fill niches left vacant by the extinct species.
4. This mass extinction is one of five major extinction events in Earth's history and is particularly noted for its drastic impact on terrestrial and marine life.
5. Following this event, plants and animals began to rapidly diversify, giving rise to new evolutionary lineages and eventually leading to the rise of mammals as dominant terrestrial vertebrates.

Review Questions

• How did the Cretaceous-Paleogene extinction influence fish evolution in the aftermath?
  • The Cretaceous-Paleogene extinction had a profound effect on fish evolution as it led to changes in marine environments. With many marine reptiles and other dominant species gone, ecological niches opened up for fish species. This provided opportunities for diversification and adaptation among surviving fish groups, leading to the emergence of new lineages that would thrive in the post-extinction world.
• Discuss how fossil indicators from the Cretaceous-Paleogene boundary help scientists understand past environments.
  • Fossil indicators from the Cretaceous-Paleogene boundary are crucial for reconstructing past environments and understanding how ecosystems responded to mass extinction events. By studying changes in fossil assemblages before and after the extinction event, scientists can gain insights into shifts in climate, biodiversity, and habitat availability. This information helps paleontologists piece together how life on Earth adapted after one of its most significant upheavals.
• Evaluate how understanding the Cretaceous-Paleogene extinction provides insights into modern biodiversity crises.
  • Studying the Cretaceous-Paleogene extinction offers valuable insights into contemporary biodiversity crises by highlighting patterns of resilience and recovery following mass extinctions. By examining how ecosystems rebounded after this event, scientists can draw parallels with current threats such as habitat loss and climate change. This understanding emphasizes the importance of conservation efforts today to mitigate potential extinctions similar to those observed during past geological upheavals.

Related terms

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

Iridium Layer: A distinct layer of sediment found in various locations around the world that contains high levels of iridium, which is rare on Earth's surface but common in asteroids, supporting the theory of an extraterrestrial impact as a cause of the extinction.

Paleocene Epoch: The geological epoch following the Cretaceous-Paleogene extinction, characterized by the recovery and diversification of mammals and birds in the absence of dinosaurs.