12.5 Radiation of Multicellular Life This time period is known as the Cambrian explosion. It led to...

12.5 Radiation of Multicellular Life

• This time period is known as the Cambrian explosion.

• It led to a huge diversity of animal species.

• Jawless fish similar to the modern day hag fish.



How did single-celled organisms come to produce such great biodiversity that we see today?


KEY CONCEPT Multicellular life evolved in distinct phases.


Life moved onto land during the Paleozoic Era.

• Multicellular organisms first appeared during the Paleozoic era.

• The era began 544 million years ago and ended 248 million years ago.

Multicellular Life


• Members of every animal group appeared with a few million years of the first multicellular, colonial life forms

• Multicellular animals radiated, the first vertebrates appeared, and plants moved onto land


This time period is known as the Cambrian explosion.

It led to a huge diversity of animal Species.

Jawless fish, similar to the modern day hagfish evolved during this Period.


• Trilobite: index fossil of the Cambrian Period

• A mass extinction at the end of the Cambrian Period led to 90% of the marine animal species and 70% of land animal species going extinct


• Life moved onto land in the middle of the Paleozoic era.

• Four-legged amphibians became more common

• Most of the coal in the U.S. formed in the Carboniferous Period.


Reptiles radiated during the Mesozoic era.

• The Mesozoic era is known as the Age of Reptiles.• It began 248 million years ago and ended 65 million years

ago.• Early mammals and flowering plants developed late in the

Mesozoic Era


• Life slowly took off in the Triassic Period.• Earliest crocodiles and dinosaurs, and the earliest

ancestors of mammals appeared.


• The Jurassic Period saw the rise of large marine predatory reptiles such as Ichthyosaurs

• Sharks and bony fishes


• The Cretaceous Period is associated with the peak of dinosaur diversity.

• Rise of the first marsupials.• Feathered dinosaurs.

• This is Archaeopteryx


• A mass extinction by a meteorite impact ended the Mesozoic Era and made the dinosaurs as well as many other life forms go extinct.


Mammals radiated during the Cenozoic era.

• The Cenozoic era began 65 million years ago and continues today.

• Placental mammals and monotremes evolved and diversified. Birds and flowering plants became common.

• Anatomically modern humans appeared late in the era.

12.5 Radiation of Multicellular Life This time period is known as the Cambrian explosion. It led to...

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