Cretaceous-paleogene extinction

Definition

The Cretaceous-Paleogene extinction event, which occurred around 66 million years ago, was a significant mass extinction that led to the disappearance of approximately 75% of Earth's species, including most dinosaurs. This event is one of the five major mass extinctions in Earth's history and is crucial for understanding the patterns and consequences of biodiversity loss over time.

5 Must Know Facts For Your Next Test

1. The Cretaceous-Paleogene extinction is marked by a dramatic shift in Earth's biodiversity, resulting in the loss of not only dinosaurs but also many marine reptiles and numerous plant species.
2. The leading hypothesis for this extinction event points to an asteroid impact, which caused significant climate changes and disrupted ecosystems worldwide.
3. The volcanic activity in the Deccan Traps, located in present-day India, may have contributed to environmental stress during this period, exacerbating the effects of the asteroid impact.
4. The aftermath of this extinction paved the way for mammals to become the dominant terrestrial vertebrates, leading to the evolution of many modern mammalian groups.
5. The recovery of biodiversity following the Cretaceous-Paleogene extinction took millions of years, with ecosystems gradually reestablishing balance and complexity.

Review Questions

• How did the Cretaceous-Paleogene extinction event compare to other major mass extinctions in terms of species loss and environmental impact?
  • The Cretaceous-Paleogene extinction was one of the most significant mass extinctions in Earth's history, with around 75% of all species vanishing. This event stands out because it led to the extinction of non-avian dinosaurs, which had dominated terrestrial ecosystems for millions of years. In comparison to other mass extinctions, such as the Permian-Triassic extinction that saw even greater percentage losses but affected different life forms, the Cretaceous-Paleogene extinction had profound implications for the evolution of mammals and birds.
• Evaluate the potential causes of the Cretaceous-Paleogene extinction and discuss how they might have interacted to trigger such a widespread loss of biodiversity.
  • The Cretaceous-Paleogene extinction is attributed mainly to two interconnected causes: an asteroid impact that created the Chicxulub Crater and extensive volcanic activity in the Deccan Traps. The asteroid impact likely caused immediate destruction and long-term climate change due to dust and debris blocking sunlight, leading to a 'nuclear winter' scenario. Meanwhile, volcanic eruptions could have released large volumes of gases like sulfur dioxide into the atmosphere, further cooling the planet and acidifying oceans. The combination of these factors created extreme environmental stresses that many species could not survive.
• Synthesize information from various sources to predict how ecosystems might change during a recovery phase following an extinction event like the Cretaceous-Paleogene.
  • In the aftermath of a mass extinction like the Cretaceous-Paleogene event, ecosystems undergo significant changes as they recover. New ecological niches open up due to the absence of dominant species like dinosaurs, allowing mammals and birds to diversify rapidly. Recovery phases often see an increase in adaptive radiations where surviving species evolve into various forms to fill empty niches. Over time, ecosystems become more complex as new interactions develop between species, leading to increased biodiversity and stability. This process highlights how life can rebound and adapt even after severe disruptions.

Related terms

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

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

Biodiversity Recovery: The process through which ecosystems regain diversity following a mass extinction event, often leading to the evolution of new species and ecological niches.