Jurassic

Definition

The Jurassic is a geologic period that lasted from about 201 million to 145 million years ago, forming the middle period of the Mesozoic Era. This time is known for significant geological and biological changes, including the dominance of dinosaurs and the appearance of the first birds and mammals.

5 Must Know Facts For Your Next Test

1. The Jurassic period is subdivided into three epochs: Early Jurassic, Middle Jurassic, and Late Jurassic, each characterized by distinct geological formations and fossil records.
2. During the Jurassic, large herbivorous dinosaurs like Brachiosaurus and Stegosaurus flourished, while predatory dinosaurs such as Allosaurus emerged as apex predators.
3. The breakup of the supercontinent Pangaea began in the Jurassic, leading to the formation of new oceans and changes in climate that impacted dinosaur evolution.
4. Jurassic marine life was diverse, with the proliferation of ammonites, ichthyosaurs, and plesiosaurs dominating the seas.
5. The end of the Jurassic paved the way for the rise of even larger dinosaurs in the subsequent Cretaceous period, marking a critical transition in Earth's biological history.

Review Questions

• How did the breakup of Pangaea during the Jurassic affect dinosaur evolution?
  • The breakup of Pangaea during the Jurassic had a profound impact on dinosaur evolution by creating new landforms and changing climate patterns. As landmasses separated, different species adapted to their unique environments, leading to increased diversity among dinosaurs. This geographical isolation allowed various groups to evolve independently, resulting in distinct evolutionary paths and adaptations suited to specific habitats.
• Discuss the significance of fossils found from the Jurassic period in understanding prehistoric ecosystems.
  • Fossils from the Jurassic period are vital in reconstructing prehistoric ecosystems because they provide direct evidence of ancient life forms and their interactions. The diverse array of fossils, including those of dinosaurs, plants, and marine organisms, helps scientists understand how species adapted to their environments and how ecosystems functioned. Analyzing these fossils reveals insights into climate conditions and biogeographical changes that occurred during this dynamic period.
• Evaluate the ecological impacts of dominant herbivorous dinosaurs during the Jurassic on their ecosystems.
  • The dominant herbivorous dinosaurs during the Jurassic played crucial roles in shaping their ecosystems through grazing habits and their size. Large herbivores like Brachiosaurus influenced vegetation patterns by consuming vast amounts of plant material, which affected plant diversity and distribution. Their movements also created pathways that benefited smaller animals and changed soil composition through their feeding behaviors. Additionally, their presence supported a complex food web by providing prey for carnivorous dinosaurs, demonstrating their integral role in maintaining ecological balance during this period.

Related terms

Mesozoic Era: The era that includes the Triassic, Jurassic, and Cretaceous periods, often referred to as the age of reptiles due to the dominance of dinosaurs.

Plate Tectonics: The theory explaining the movement of the Earth's lithosphere, which influenced the distribution of landmasses and ocean basins during the Jurassic.

Fossils: Preserved remains or traces of ancient organisms that provide evidence about life forms during the Jurassic period and help reconstruct past environments.