K-Pg Extinction

Definition

The K-Pg extinction, formerly known as the K-T extinction, was a mass extinction event that occurred approximately 66 million years ago, marking the boundary between the Cretaceous and Paleogene periods. This event is famous for leading to the demise of approximately 75% of Earth's species, including the non-avian dinosaurs, and significantly reshaped terrestrial ecosystems and biodiversity.

5 Must Know Facts For Your Next Test

1. The K-Pg extinction is one of the most significant mass extinctions in Earth's history, leading to the loss of around 75% of all species at that time.
2. The primary hypothesis for this extinction event centers around a large asteroid impact, which created environmental changes that were catastrophic for many species.
3. In addition to the asteroid impact, volcanic activity in what is now India (the Deccan Traps) may have contributed to climate changes during this period.
4. The extinction paved the way for mammals to diversify and dominate terrestrial ecosystems during the Paleogene period, leading to the eventual rise of modern mammals.
5. Fossil evidence from this period reveals a rapid transition in ecosystems and species compositions, illustrating how life rebounded and evolved following the K-Pg extinction.

Review Questions

• What are some potential causes of the K-Pg extinction, and how do they relate to the changes observed in terrestrial ecosystems?
  • The K-Pg extinction is primarily attributed to an asteroid impact that created the Chicxulub Crater and led to dramatic environmental changes such as wildfires, tsunamis, and a 'nuclear winter' effect from debris blocking sunlight. Additionally, extensive volcanic activity in the Deccan Traps released gases that contributed to long-term climate shifts. These combined factors caused significant disruptions in food chains and habitats, leading to widespread extinctions among both vertebrates and invertebrates.
• Analyze how the K-Pg extinction influenced mammalian evolution in subsequent geological periods.
  • The K-Pg extinction resulted in the disappearance of dominant groups like dinosaurs, which created ecological niches that mammals could exploit. With reduced competition, mammals diversified rapidly during the Paleogene period into various forms and sizes, adapting to new environments. This evolutionary leap set the stage for mammals to become the dominant terrestrial animals and eventually led to the emergence of many modern orders we see today.
• Evaluate how studying fossils from before and after the K-Pg extinction can provide insight into paleoecological changes and species resilience.
  • Analyzing fossils from before and after the K-Pg extinction allows scientists to reconstruct ancient ecosystems and understand how life adapted to drastic environmental shifts. By examining morphological traits, community structures, and ecological roles of species that survived versus those that did not, researchers can gain insights into resilience mechanisms. This understanding is crucial for predicting how current biodiversity may respond to ongoing environmental challenges, making it relevant for conservation efforts today.

Related terms

Chicxulub Crater: A massive impact crater located on the Yucatán Peninsula in Mexico, formed by the asteroid impact believed to be a primary cause of the K-Pg extinction.

Iridium Layer: A geological marker found in the sediment layer dating to the time of the K-Pg extinction, enriched with iridium, which supports the asteroid impact hypothesis.

Paleogene Period: The geological period that follows the Cretaceous, characterized by the recovery and evolution of mammals and birds after the mass extinction event.