Cenozoic

Definition

The Cenozoic is the most recent geological era, spanning from about 66 million years ago to the present. It is marked by significant changes in climate, the evolution of mammals and birds, and the development of modern ecosystems. This era is divided into three periods: the Paleogene, Neogene, and Quaternary, each characterized by distinct geological and biological developments that have influenced the course of life on Earth.

5 Must Know Facts For Your Next Test

1. The Cenozoic began after the mass extinction event that wiped out the dinosaurs, allowing mammals to become the dominant terrestrial vertebrates.
2. This era has seen significant climate fluctuations, including ice ages that shaped landscapes and influenced species adaptations.
3. Many modern mammal families we recognize today originated during the Cenozoic, reflecting rapid evolutionary changes in response to environmental shifts.
4. The Cenozoic has been crucial for human evolution, with key developments occurring in the Quaternary period, such as the rise of hominins.
5. Fossil evidence from the Cenozoic is vital for biostratigraphy and relative dating, helping scientists understand the timeline of Earth's history and evolutionary patterns.

Review Questions

• How did the end of the Cretaceous period set the stage for the rise of mammals in the Cenozoic?
  • The end of the Cretaceous period marked a mass extinction event that eliminated about 75% of Earth's species, including all non-avian dinosaurs. This created ecological niches that allowed mammals to evolve and diversify without competition from large reptiles. The subsequent rise in mammalian diversity during the Paleogene period highlighted how quickly life can adapt when significant ecological opportunities arise.
• What are some key climatic events during the Cenozoic that influenced evolutionary processes?
  • During the Cenozoic, there were several key climatic events that had profound effects on evolution. The transition from a warm greenhouse world in the early Cenozoic to cooler conditions characterized by ice ages in the late Cenozoic created selective pressures for many species. These climatic shifts led to adaptations such as increased body size in mammals for better thermoregulation and changes in vegetation that influenced herbivore diets and habitats.
• Evaluate how fossil evidence from the Cenozoic contributes to our understanding of biostratigraphy and relative dating methods.
  • Fossil evidence from the Cenozoic provides critical data for biostratigraphy, which relies on fossil distribution to correlate rock layers across different geographic regions. By analyzing these fossils' ages and types, scientists can establish relative timelines for various species' appearances and extinctions. This information is essential for understanding evolutionary history and ecological changes over time, allowing researchers to piece together a more comprehensive picture of Earth's biological past.

Related terms

Paleogene: The first period of the Cenozoic, lasting from about 66 to 23 million years ago, during which mammals began to diversify and dominate after the extinction of dinosaurs.

Neogene: The second period of the Cenozoic, lasting from about 23 to 2.6 million years ago, notable for the further evolution of mammals and birds, as well as significant climatic changes.

Quaternary: The most recent period of the Cenozoic, starting around 2.6 million years ago, characterized by glaciations and the evolution of Homo sapiens.