What are some of the most important events in the history of life during Mesozoic Era? What marks the beginning of this Era? What periods did it include (with timeline)? How did continents change? Which main groups of marine and terrestrial animals (invertebrates and vertebrates) and plants evolved and became extinct? How and when did the Mesozoic Era end?
The Correct Answer and Explanation is:
The Mesozoic Era, often called the “Age of Reptiles,” was a critical chapter in Earth’s history, lasting from about 252 million years ago (mya) to 66 mya. It began after the Permian–Triassic extinction event, the most severe mass extinction in Earth’s history, and ended with another mass extinction that wiped out the non-avian dinosaurs.
Periods of the Mesozoic Era:
- Triassic Period (252–201 mya)
- Jurassic Period (201–145 mya)
- Cretaceous Period (145–66 mya)
Continental Changes:
At the beginning of the Mesozoic, the continents were joined in a supercontinent known as Pangaea. During the era, Pangaea slowly broke apart, forming Laurasia in the north and Gondwana in the south. This breakup caused changes in sea levels, climate, and ecosystems. By the end of the Mesozoic, the continents were drifting toward their modern positions.
Evolution and Extinction:
Marine Life:
- Invertebrates: Ammonites and belemnites (cephalopods) flourished. Coral reefs were formed by rudist bivalves.
- Vertebrates: Marine reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs evolved and dominated the oceans.
Terrestrial Life:
- Invertebrates: Insects diversified, with the appearance of early ants and bees.
- Vertebrates: Dinosaurs evolved in the Triassic and dominated terrestrial ecosystems during the Jurassic and Cretaceous. The first birds appeared in the Jurassic. Mammals also appeared early but remained small and less dominant.
- Plants: Gymnosperms (like cycads, ginkgos, and conifers) were widespread early on. Angiosperms (flowering plants) evolved in the Cretaceous and began to dominate by the era’s end.
End of the Mesozoic:
The era ended 66 million years ago with the Cretaceous–Paleogene (K–Pg) extinction event, likely caused by an asteroid impact and volcanic activity. This led to the extinction of the non-avian dinosaurs, ammonites, and many marine reptiles, marking the transition to the Cenozoic Era.
