Evolution of Multicellular Life Precambrian Time Almost 90

Evolution of Multi-cellular Life

Precambrian Time Ø Almost 90% of the Earth’s history fits in Precambrian Time l l Simple anaerobic life appear Oxygen appeared after photosynthetic organisms appeared. Aerobic life appeared. Simple multi-cellular life appeared.

Paleozoic Era Ø Begins with simple invertebrates; ends with fish, amphibians, reptiles and seedless plants and a mass extinction l l Cambrian Period Ordovician and Silurian Periods Devonian Period Carboniferous and Permian Periods

Cambrian Period Ø 1 st examples of shells and outer skeletons Ø 1 st example of many animals evolved l Invertebrates – jellyfish, worms and sponges Ø “Cambrian Explosion” – rapid diversification of life forms

Ordovician and Silurian Periods Ø Ancestors of squid, octopus and lobster appeared. Ø The first animals moved onto land – arthropods similar to modern insects. Ø 1 st vertebrate animals – jawless fishappeared. Ø Low growing plants appeared in wet areas.

Devonian Period Ø Plants were able to move into drier areas. Ø Invertebrates were more numerous in the ocean Ø Bony fishes and sharks appeared during this period. Ø Vertebrates began to leave the ocean, but insects were more numerous on land.

Carboniferous and Permian Periods Ø Reptiles appeared. Ø Insects continued to evolved; included winged forms. Ø Giant ferns formed large forests.

Mesozoic Era Ø Marked by the appearance of flowering plants and increasing dominance of reptiles in the form of dinosaurs l l l Triassic Period Jurassic Period Cretaceous Period

Triassic Period Ø Fish, insects, reptiles and cone-bearing plants survived the extinction. Ø 1 st dinosaurs appeared 225 million years ago. Ø Small mammals – size of a mouse – appeared during this time.

Jurassic Period Large plant-eating dinosaurs were the dominant life-form. Ø The 1 st bird evolved from dinosaurs during this period. Ø

Cretaceous Period Meat-eating dinosaurs dominated the land. Ø Flying reptiles appeared. Ø Flowering plants appeared Ø

Cenozoic Era Ø Marked the rise of the mammals after the dinosaurs became extinct l l Tertiary Period Quaternary Period

Tertiary Period Ø Warm mild weather encouraged the growth of large, herbivorous animals. Ø Whales and dolphins evolved.

Quaternary Period Ø The current period of time Ø Began with the advance of the glaciers Ø Mammals are the dominant species of this time.