12 5 Radiation of Multicellular Life KEY CONCEPT

12. 5 Radiation of Multicellular Life KEY CONCEPT Multicellular life evolved in distinct phases.

12. 5 Radiation of Multicellular Life moved onto land during the Paleozoic Era. • Multicellular organisms first appeared during the Paleozoic era. “ancient” • The era began 542 million years ago and ended 251 million years ago. Life started in the ocean! • The Cambrian explosion led to a huge diversity of animal species. • Lost 90% marine animals and 70% of land animals (mass extinction – end of Paleozoic Era – Permian period) see pg. 366

12. 5 Radiation of Multicellular Life • • • Life moved onto land in the middle of the Paleozoic era. Coal and petroleum used today came from this time. Four-legged vertebrates such as amphibians were common. First sharks, insects, trees and forests arose. Jawless and freshwater fishes evolved.

12. 5 Radiation of Multicellular Life Reptiles radiated during the Mesozoic era. • The Mesozoic era “middle” is known as the Age of Reptiles. • It began 251 million years ago and ended 65 million years ago. • Dinosaurs, birds, flowering plants, and first mammals (shrewlike) appeared. • Mass extinction (meteorite)

12. 5 Radiation of Multicellular Life Mammals radiated during the Cenozoic era. • The Cenozoic era began 65 million years ago and continues today. (Tertiary and Quaternary Periods) • Placental mammals and monotremes (egg-laying mammals) evolved and diversified. Adaptive radiation of mammals into 4000 different species. • Anatomically modern humans, Homo sapiens, appeared about 100, 000 years ago.