Cenozoic EraMammals became common during the Cenozoic.
During the Cenozoic, mammals evolved adaptations that allowed them to live in various environments—on land, in water, and even in the air.
The Cenozoic often is called the Age of Mammals.The Cenozoic is divided into the Tertiary Period and the Quaternary Period.
Mezoic EraDinosaurs lived during this time. Mammals began to evolve during this era.
During the Mesozoic Era, dinosaurs became dominant. The Mesozoic is also marked by the appearance of flowering plants.
The Mesozoic Era is often called the Age of Reptiles.
Paleozoic EraMany vertebrates and invertebrates lived during this time.Rich fossil evidence shows that early in the Paleozoic Era, there was a diversity of marine life.
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Jurrasic PeriodDinosaurs became the dominant animals on land. One of the first birds, Archaeopteryx, appeared. Many paleontologists think that birds are close relatives of dinosaurs.
Cretaceous PeriodDominant animals during this period included: reptiles, birds, turtles, crocodiles, fishes, and marine invertebrates.New forms of plant life included leafy trees, shrubs, and small flowering plants.
The Cretaceous Period ended with a mass extinction. More than half of all plant and animal groups were wiped out, including all of the dinosaurs.
Triassic PeriodOrganisms that survived the Permian mass extinction became the main life forms early in the Triassic. These organisms included fishes, insects, reptiles, and cone-bearing plants.
Carboniferous and Permian PeriodsReptiles evolved from certain amphibians. Winged insects evolved into many forms.Giant ferns and other plants formed vast swampy forests.Remains of ancient plants formed thick deposits of sediment that changed into coal over millions of years.
The mass extinction at the end of the Paleozoic affected both plants and animals on land and in the seas. As much as 95% of the complex life in the oceans disappeared.
Devonian PeriodSome plants adapted to drier areas and invaded more habitats. Insects appeared on land. The Devonian is often called the Age of Fishes because many groups of fishes were present in the oceans. Most fishes had jaws, bony skeletons, and scales.
During the Devonian, vertebrates began to invade the land.Some of these early four-legged vertebrates evolved into the first amphibians.
Ordovician and Silurian PeriodsSome arthropods became the first land animals. The first vertebrates appeared. The first land plants evolved from aquatic ancestors.
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Precambrian TimeGeologic time begins with Precambrian Time, which covers about 88% of Earth’s history.
Tertiary PeriodThe climate was generally warm and mild. Marine mammals such as whales and dolphins evolved. Grasses evolved, providing food for grazing mammals.Some mammals became very large, as did some birds.
Quaternary PeriodEarth’s climate cooled, causing a series of ice ages. About 20,000 years ago, Earth’s climate began to warm and sea levels began to rise. In the oceans, algae, coral, mollusks, fishes, and mammals thrived.Insects, birds, and land mammals were common.