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Big Bang Theory Briefly (youtube, ep. 1)The Big Bang Theory states that 13.7 billion years ago, a huge expansion of the universe occured due to its hot, dense state. This expansion caused the temperature to drop low enough to allow energy to convert into subatomic particles. Protons and Neutrons combined to form the first atomic nuclei only a few minutes after the Big Bang, but it took thousands of years for them to combine with electrons to form electrically neutral atoms. The first elements later formed stars and galaxies.
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Earth forms from a nebula in space orbiting the sun.
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By this point, the earth has formed and continantal shields have appeared. Stromatolites, formed by algae, are the most common organism.
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the cambrian explosionMarine invertebrates with shells appear and trilobites and brachiopods are common. This is where the first back-boned species appear. (vertebrates)
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Echinoderms appear and brachiopiods increase as trilobites fade out. Graptolites flourish and atmosphere becomes rich in oxygen; like it is now.
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During this period, the first true fish evolve and early land plants and animals come into existence. The Caledonian orogeny marks the end of the period.
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"age of fishes"- fish were the dominant animal species. The first forests appear along with ferns and seed-bearing plants. Also, amphibians start to pop up.
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MISSISSIPPIAN: Amphibians spread like the Black Death. Brachiopods are popular in oceans. Most of the land is covered by forests and swamps.
PENNSYLVANIAN: Giant cockroaches and dragonflies are prevalent. The first deposits of coal form and reptiles evolve. -
Pangaea forms and the end of the period is marked by a mass extinction including 96% of all marine species and 70% of all terrestrial vertebrate species. This is the only known mass extinction of insects.
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After the Permian extinction, dinosaurs AND mammals appear- not just dinosaurs. Ammonites, cyads, and conifers are popular.
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jurassic period article
NOW, dinosaurs are dominant and mammals are unimportant losers. Primitive birds come along as well as flying reptiles. -
First flowering plants ,or angiosperms, appear. Another mass extinction occurs marking the end of the Mesozoic Era. All dinosaurs go bye-bye and pop-goes-the-mammals.. (next era)
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"Age of mammals"- mammals are dominant now and the first primates appear
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Deer, pigs, camels, cats, and dogs evolve. The Himalayan mountains form. The global climate becomes dramatically cooler and drier causing many mammals to become extinct. But, many species benefit from the climate change and flourish. Marine invertebrates also flourish.
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New circumpolar currents cause modern antarctic icecap to form. The Mediterranean Sea fills and drains several times. The largest land mammals exist in this time period.
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Large carnivores such as bears, lions, etc. come to be. Herbivores like the giant ground sloth increase. Toward the end there is an "ice age' as continental ice sheets spread and ocean levels drop significantly. Many speciesmigrate across a couple new land bridges.
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Woolly mammoths, rhinos and, finally, HUMANS appear. Through the cold, some species survived with natural characteristics (like thick fur), some by migration, and others became extinct.
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The last ice age ends and complex human societies develop. (this epoch includes now) Humans get smarter and start using agriculture and invent tools made of bronze and iron.
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Horses, flying squirrels, bats, and whales come along. Small reptiles multiply. Toward the end of the epoch, the global temperature drops about 4 degrees celsius.
