End-cretaceous extinction

Definition

The end-cretaceous extinction refers to a significant mass extinction event that occurred approximately 66 million years ago, leading to the abrupt disappearance of about 75% of Earth's species, including most dinosaurs. This event marks a crucial turning point in Earth's history, significantly shaping the evolutionary trajectory of life on the planet and paving the way for mammals to become the dominant terrestrial vertebrates.

5 Must Know Facts For Your Next Test

1. The end-cretaceous extinction is one of the five major mass extinctions in Earth's history and is often referred to as the K-T extinction event.
2. The leading hypothesis for this extinction event points to a combination of an asteroid impact and extensive volcanic activity, both of which caused drastic climate changes.
3. The sudden drop in temperatures and alterations in ecosystems following the impact led to the collapse of food chains, significantly affecting both terrestrial and marine organisms.
4. Birds are considered the only surviving lineage of theropod dinosaurs after the end-cretaceous extinction, showcasing an important evolutionary transition.
5. The aftermath of the end-cretaceous extinction saw mammals diversify and occupy ecological niches left vacant by extinct reptiles, leading to the rise of modern mammal groups.

Review Questions

• What were the main causes of the end-cretaceous extinction, and how did they affect biodiversity?
  • The end-cretaceous extinction is primarily attributed to two significant events: an asteroid impact, which created the Chicxulub Crater, and extensive volcanic activity from the Deccan Traps. The asteroid impact caused immediate catastrophic effects, including wildfires and tsunamis, while volcanic eruptions released vast amounts of ash and gases into the atmosphere, leading to a 'nuclear winter' scenario. Together, these events drastically altered habitats and disrupted food chains, resulting in a substantial loss of biodiversity.
• Analyze how the end-cretaceous extinction impacted mammalian evolution in the subsequent periods.
  • Following the end-cretaceous extinction, mammals experienced a significant evolutionary radiation as they filled ecological niches left vacant by dinosaurs and other extinct species. With reduced competition from large reptiles, mammals diversified rapidly in size and form, leading to the emergence of many modern mammal groups during the Paleogene period. This allowed mammals to become dominant terrestrial vertebrates, setting the stage for their eventual evolution into various forms, including primates and ultimately humans.
• Evaluate the significance of studying mass extinction events like the end-cretaceous extinction in understanding current biodiversity crises.
  • Studying mass extinction events such as the end-cretaceous extinction is crucial for understanding patterns and processes that lead to biodiversity loss. By examining past events, scientists can identify factors contributing to extinctions—like habitat destruction, climate change, and sudden environmental shifts—allowing them to draw parallels with contemporary biodiversity crises driven by human activities. This knowledge can inform conservation efforts and strategies aimed at mitigating current threats to biodiversity, highlighting the importance of historical context in shaping our response to ecological challenges today.

Related terms

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

Deccan Traps: A large volcanic province in India, whose extensive lava flows and gases are thought to have contributed to environmental changes that exacerbated the end-cretaceous extinction.

Mass extinction: A widespread and rapid decrease in biodiversity on Earth, characterized by the extinction of a large number of species across various taxa within a relatively short geological timeframe.