End-cretaceous event

Definition

The end-cretaceous event refers to a mass extinction event that occurred approximately 66 million years ago, marking the end of the Cretaceous period and the demise of about 75% of Earth's species, including the non-avian dinosaurs. This event is significant as it drastically reshaped terrestrial ecosystems, allowing for the rise of mammals and birds in the subsequent Paleogene period.

5 Must Know Facts For Your Next Test

1. The end-cretaceous event is often linked to two main causes: an asteroid impact and extensive volcanic activity, both contributing to dramatic environmental changes.
2. The extinction had a profound effect on terrestrial vertebrate paleoecology, leading to the extinction of major groups like dinosaurs and allowing mammals to diversify and occupy new ecological niches.
3. Invertebrate life was also significantly affected, with many marine species disappearing, changing the dynamics of ocean ecosystems.
4. Evidence of this mass extinction is found in a distinct layer of sediment rich in iridium, known as the Cretaceous-Paleogene boundary, marking the transition between the two periods.
5. The aftermath of the end-cretaceous event saw rapid evolutionary adaptations and the emergence of new species, fundamentally altering the course of life on Earth.

Review Questions

• How did the end-cretaceous event influence the evolution and distribution of terrestrial vertebrates?
  • The end-cretaceous event led to a major shift in terrestrial vertebrate populations by causing the extinction of non-avian dinosaurs and many other species. This opened up ecological niches that allowed mammals to evolve and diversify rapidly, ultimately leading to their dominance in terrestrial ecosystems. The event reshaped food webs and community structures, creating opportunities for various mammalian lineages to adapt and thrive in environments previously dominated by dinosaurs.
• Discuss the potential mechanisms that led to the mass extinction during the end-cretaceous event, focusing on both impact theory and volcanic activity.
  • The leading theories for the end-cretaceous event include the asteroid impact hypothesis, which posits that a massive asteroid struck Earth, creating the Chicxulub Crater and leading to catastrophic environmental changes. This impact would have caused fires, tsunamis, and a 'nuclear winter' effect due to debris blocking sunlight. In addition, volcanic activity from the Deccan Traps released significant amounts of ash and gases into the atmosphere, contributing to long-term climate change. Together, these mechanisms likely created a hostile environment for many species.
• Evaluate the long-term ecological consequences of the end-cretaceous event on both vertebrate and invertebrate life, considering subsequent evolutionary trends.
  • The long-term ecological consequences of the end-cretaceous event were profound for both vertebrates and invertebrates. In vertebrates, mammals emerged as dominant terrestrial animals during the Paleogene period due to their ability to adapt to new ecological roles left vacant by extinct groups. For invertebrates, marine ecosystems underwent significant restructuring; many taxa faced extinctions while others adapted or radiated into new forms. These shifts set the stage for modern biodiversity patterns and initiated new evolutionary trends that shaped future ecosystems over millions of years.

Related terms

Chicxulub Crater: A large impact crater located on the Yucatan Peninsula in Mexico, widely believed to be the site of the asteroid impact that triggered the end-cretaceous event.

Deccan Traps: A massive volcanic region in present-day India that contributed to environmental changes during the end-cretaceous event, potentially affecting global climate and ecosystems.

Mesozoic Era:

The era of geological time spanning from about 252 to 66 million years ago, characterized by the dominance of dinosaurs and significant evolutionary changes in both vertebrate and invertebrate life.