Cretaceous Period

Definition

The Cretaceous Period is a geologic time frame that lasted from approximately 145 to 66 million years ago, marking the final period of the Mesozoic Era. This period is characterized by the dominance of dinosaurs, the appearance of flowering plants, and significant geological and climatic changes, all of which played a crucial role in shaping the earth’s biogeographic patterns during that time.

5 Must Know Facts For Your Next Test

1. The Cretaceous Period is divided into two main epochs: Early Cretaceous and Late Cretaceous, each marked by distinct climatic and ecological changes.
2. This period saw the emergence of flowering plants (angiosperms), which began to diversify and spread widely, transforming ecosystems.
3. The Cretaceous was also characterized by significant tectonic activity, leading to the separation of landmasses and influencing species distribution through continental drift.
4. A major event at the end of the Cretaceous Period, believed to be triggered by an asteroid impact, caused a mass extinction that wiped out about 75% of Earth's species.
5. Fossil evidence from the Cretaceous has helped scientists understand ancient ecosystems, including marine environments where large marine reptiles thrived alongside dinosaurs.

Review Questions

• How did geological changes during the Cretaceous Period influence biogeographic patterns?
  • Geological changes during the Cretaceous Period, including significant tectonic activity and continental drift, played a crucial role in shaping biogeographic patterns. The separation of landmasses created isolated habitats that led to diverse evolutionary paths for different species. This fragmentation allowed for the development of unique ecosystems and influenced species distributions, ultimately impacting biodiversity throughout the period.
• Discuss the role of flowering plants in shaping ecosystems during the Cretaceous Period.
  • Flowering plants emerged during the Cretaceous Period and significantly transformed terrestrial ecosystems. Their diversification provided new food sources for herbivorous dinosaurs and other animals, promoting changes in ecological interactions. The spread of angiosperms also contributed to the development of complex habitats and influenced pollination dynamics, which were critical for ecosystem stability during this time.
• Evaluate the impact of the mass extinction event at the end of the Cretaceous Period on Earth's biodiversity and future ecological developments.
  • The mass extinction event at the end of the Cretaceous Period had profound effects on Earth's biodiversity, eliminating approximately 75% of species, including most dinosaurs. This drastic loss created opportunities for other groups, such as mammals and birds, to flourish and diversify in the post-Cretaceous world. The aftermath shaped ecological developments, leading to new forms of life and ultimately setting the stage for modern ecosystems as we know them today.

Related terms

Mesozoic Era:

The Mesozoic Era is the geological era that spanned from about 252 to 66 million years ago, encompassing three major periods: Triassic, Jurassic, and Cretaceous, known for the rise and fall of dinosaurs.

Paleobiogeography:

Paleobiogeography studies the distribution of ancient organisms across different geographical areas and how this distribution was affected by historical events such as continental drift.

Mass Extinction: Mass extinction refers to a rapid decrease in the biodiversity on Earth, with significant extinction events such as the one at the end of the Cretaceous Period, which led to the extinction of about 75% of species, including most dinosaurs.