Geologic Timescale

Archaean Eon 4.6-2.5 billion years ago (bya) Earth’s origin 3.7 bya: First protobionts 3.5 bya: First Prokaryotes 2.5 bya: atmospheric Oxygen increases

Proterozoic Eon 2.5 bya to 542 mya 2.2 bya: first Eukaryotes Prokaryotes with plastids, mitochondria, and DNA 600 mya: algae and soft bodied invertebrate animals Snow ball Earth Hypothesis: Life can only exist where sunlight can reach deep ocean (where there was no ice), like vents and plate boundaries

Phanerozoic Eon Eras: All of life evolves to current state Paleozoic: 542 mya to 251 mya Mesozoic: 251 mya to 65 mya Cenozoic: 65 mya to today All of life evolves to current state Two mass extinctions: Permian Cretaceous

Paleozoic Era Periods: Cambrian: Cambrian explosion and diversity of species Ordovician: Plants and Arthropods colonize land Silurian: vascular plants diversify Devonian: Bony Fish, tetrapods, insects Carboniferous: GIANT FOREST OF VASCULAR, Reptiles Permian: More reptiles, origin of modern insects, MASS EXTINCTION

Permian Mass Extinction 96% of marine species gone Increased volcanic activity in modern day Siberia More CO2 in atmosphere, warmed planet Less difference in equator and poles, slowed ocean currents No currents, less oxygen for marine life

Mesozoic Era Periods: Triassic: Cone bearing plants, dinosaurs diversify, and mammal like reptiles Jurassic: Continued dominance of Cone bearing plants and dinosaurs Cretaceous: Flowering plants emerge, Mass Extinction

Cretaceous Mass Extinction 50 % of marine life gone, most land plants and dinosaurs gone Theory: asteroid or comet hit modern day Mexico and created a cloud of dust on Earth This dust became a layer of clay with Iridium, which is an element not common on Earth There was also an increase in volcanic activity in India

Cenozoic Era Periods: Paleogene: 65 - 23 mya Neogene: 23 mya – today Diversity of mammals, birds and insects Flowering plants become dominant Origin of Primate groups Neogene: 23 mya – today Origin of genus Homo Ice Ages Modern Day