Earth Science

Life on Earth

History of Mesozoic Life

Study Tip
The Mesozoic Era can be divided into three separate periods: Triassic Jurassic, and Cretaceous. Each period had similarities between one another as well as unique characteristics.

The Age of the Dinosaurs

The Mesozoic Era is best known as the age of the dinosaurs. These large reptiles dominated the land and seas of the Earth during this era. Dinosaurs filled all the niches that are currently filled by mammals today. There were plant eating, meat eating, endothermic, bipedal, and quadrupedal dinosaurs. Dinosaur bones had canals, which indicated that they were active creatures.

Study Tip
The Mesozoic Era can be divided into three separate periods: Triassic Jurassic, and Cretaceous. Each period had similarities between one another as well as unique characteristics.

Time Line

Time line of dinosaurs

Terrestrial Life

  • Seed plants and trees diversified and spread widely.
  • Lush forests covered much of the land, especially at higher altitudes.
  • Flowering plants evolved during the Cretaceous.
Archaeamphoralongicervia, a cretaceous plant

Marine Life

  • Tiny phytoplankton became the base of the marine food web.
  • The supercontinent Pangaea began to break apart, so more beaches and continental shelf areas were available for colonization by new species of marine organisms.
  • Marine reptiles colonized the seas and diversified. Some became huge, filling the niches that are filled by large marine mammals today.

Earth Science

Climate

Climate alternated between cool, warm, and tropical seasons, but overall the planet was much warmer than today. The Mesozoic Era’s atmosphere had more oxygen than the atmosphere today.

From Reptiles to Mammals

The Mesozoic era was known as the age of the reptiles. Compared to their amphibian ancestors, reptiles were able to move on to land because they had a thick skin which kept much of the body moisture and amniotic eggs which ensured successful reproduction. Mammals would appear near the end of the Triassic.

Cretaceous Mass Extinction

  • Up to fifty percent of the planet’s animal and plant species disappeared in this extinction.
  • Cause of extinction is uncertain, but scientists trace the origins to drastic climate changes caused by a massive meteor impact.
  • The impact created a hot environment unsuitable for animals to live in.
  • Dust in the atmosphere hindered photosynthesis.
  • Sulfur from the impact mixed with water to create acid rain, which ruined plankton.
Concept Check
  • What major event occurred at the end of the Cretaceous period?
  • What sort of organisms dominated the Mesozoic land scape?
  • What happened to Pangaea during this era?