Life’s Timeline

Earth is Born aka The Precambrian Era

The First 100 million years Cosmic junk hits Giant collisions melt the planet Density stratification

The First Atmosphere –Hydrogen cyanide –Carbon Dioxide –Carbon Monoxide –Nitrogen –Hydrogen Sulfite –Water –Hydrogen cyanide –Carbon Dioxide –Carbon Monoxide –Nitrogen –Hydrogen Sulfite –Water TOXIC!!!

4 b.y.a. 1 st solid rocks Lots of volcanos Cosmic junk bombards surface Too hot for liquid H 2 O! 1 st solid rocks Lots of volcanos Cosmic junk bombards surface Too hot for liquid H 2 O!

3.8 b.y.a. Cool enough for liquid water Storms cover Earth in water Oceans form Lots of dissolved iron in oceans Cool enough for liquid water Storms cover Earth in water Oceans form Lots of dissolved iron in oceans

3.6 – 3.5 b.y.a. Bacteria-like life forms common in oceans –Evidence: microfossils! Bacteria-like life forms common in oceans –Evidence: microfossils!

2.2 b.y.a. Photosynthetic bacteria producing Oxygen –Oxygen + Iron in oceans = RUST appears! –Rust falls to ocean floor = oceans turn blue-green –Oxygen builds up in atmosphere… Photosynthetic bacteria producing Oxygen –Oxygen + Iron in oceans = RUST appears! –Rust falls to ocean floor = oceans turn blue-green –Oxygen builds up in atmosphere…

Atmospheric O 2 Accumulates Ozone forms protective layer! Sky turns blue! Cells DIE OR MOVE to oxygen-free habitats (Their descendants are still there!) New cells use oxygen! Ozone forms protective layer! Sky turns blue! Cells DIE OR MOVE to oxygen-free habitats (Their descendants are still there!) New cells use oxygen!

Prokaryotic cells evolve interior membranes e.g. nuclei!!! Endosymbiosis leads to Eukaryotic cells with –Mitochondria –chloroplasts Prokaryotic cells evolve interior membranes e.g. nuclei!!! Endosymbiosis leads to Eukaryotic cells with –Mitochondria –chloroplasts 2 b.y.o

Eukaryotic cells continue to evolve Sexual Reproduction!!! –Evolution SPEEDS UP!!!, as sexual reproduction allows allele shuffling so that offspring are not identical to their parents. Eukaryotic cells continue to evolve Sexual Reproduction!!! –Evolution SPEEDS UP!!!, as sexual reproduction allows allele shuffling so that offspring are not identical to their parents. Later…

A few hundred-million years later… Evolution of MULTICELLULAR ORGANISMS!!! Evolution of MULTICELLULAR ORGANISMS!!!

Earth as a Toddler The Paleozoic Era

The Cambrian Period: m.y.a. Diversification Firsts: –Tough body parts (outer skeletons, shells) –Animals Invertebrates: jelly fish, worm, sponge Brachiopods: (2 shells) Trilobites Diversification Firsts: –Tough body parts (outer skeletons, shells) –Animals Invertebrates: jelly fish, worm, sponge Brachiopods: (2 shells) Trilobites

The Ordovician and Silurian Periods: m.y.a. Firsts: –Backbones!!! first vertebrates: jawless fishes –Insects! (invertebrates) –Land Plants! (low to ground in damp areas) Firsts: –Backbones!!! first vertebrates: jawless fishes –Insects! (invertebrates) –Land Plants! (low to ground in damp areas)

The Devonian Period: m.y.a. –Ferns and dry-land plants –SHARKS!!! jaws, bones, and scales –LAND ANIMALS! 1st AMPHIBIANS!!! –Ferns and dry-land plants –SHARKS!!! jaws, bones, and scales –LAND ANIMALS! 1st AMPHIBIANS!!!

The Carboniferous and Permian Periods: m.y.a. –REPTILES!!! –Huge Winged Insects! –Vast Forests! (giant ferns) –REPTILES!!! –Huge Winged Insects! –Vast Forests! (giant ferns)

The Permian MASS EXTINCTION: End of the Paleozoic Extinct: –95% of ocean life –Many amphibians, land animals and plants Survivors: some fish and reptiles… Extinct: –95% of ocean life –Many amphibians, land animals and plants Survivors: some fish and reptiles…

The Mesozoic Era Age of the Reptiles

The Triassic Period: m.y.a. Mass Extinction of –fishes, insects, reptiles, cone-bearing plants DINOSAURS!!! (225 m.y.a.) MAMMALS! (late Triassic) Evolved from reptiles Very small Mass Extinction of –fishes, insects, reptiles, cone-bearing plants DINOSAURS!!! (225 m.y.a.) MAMMALS! (late Triassic) Evolved from reptiles Very small

The Jurassic Period: m.y.a. Dominant Players: Dinosaurs (on land) BIRDS!!! –Archaeopteryx Evolved from dinosaurs Dominant Players: Dinosaurs (on land) BIRDS!!! –Archaeopteryx Evolved from dinosaurs

The Cretaceous Period: m.y.a. –Land: Dinosaurs (T. rex) –Air: Birds, Flying Dinosaurs –Water: Turtles, Crocodiles, Dinosaurs, Fish, Invertebrates Firsts: –Leafy Trees, FLOWERS!!! (fruits) –Land: Dinosaurs (T. rex) –Air: Birds, Flying Dinosaurs –Water: Turtles, Crocodiles, Dinosaurs, Fish, Invertebrates Firsts: –Leafy Trees, FLOWERS!!! (fruits)

The Mesozoic MASS EXTINCTION –Over 50% of all plants and animals –All Dinosaurs –Over 50% of all plants and animals –All Dinosaurs

The Cenozoic Era The Age of Mammals

The Tertiary Period: m.y.a. Warm, mild climate –Whales, Dolphins –Grazing mammals –The earliest Human Ancestor (3.5 m.y.a.) Warm, mild climate –Whales, Dolphins –Grazing mammals –The earliest Human Ancestor (3.5 m.y.a.)

The Quaternary Period: 1.8 m.y.a. - Present ICE AGES –oceans falls 100m –20 k.y.a. – warms up – oceans rise again Firsts: HUMANS (~150 k.y.a.) ICE AGES –oceans falls 100m –20 k.y.a. – warms up – oceans rise again Firsts: HUMANS (~150 k.y.a.)

Life’s Timeline