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Basic timeline

2014-3-16 17:48| view publisher: amanda| views: 1002| wiki(57883.com) 0 : 0

description: In its 4.6 billion years circling the sun, the Earth has harbored an increasing diversity of life forms:for the last 3.6 billion years, simple cells (prokaryotes);for the last 3.4 billion years, cyano ...

In its 4.6 billion years circling the sun, the Earth has harbored an increasing diversity of life forms:

for the last 3.6 billion years, simple cells (prokaryotes);
for the last 3.4 billion years, cyanobacteria performing photosynthesis;
for the last 2 billion years, complex cells (eukaryotes);
for the last 1 billion years, multicellular life;
for the last 600 million years, simple animals;
for the last 550 million years, bilaterians, animals with a front and a back;
for the last 500 million years, fish and proto-amphibians;
for the last 475 million years, land plants;
for the last 400 million years, insects and seeds;
for the last 360 million years, amphibians;
for the last 300 million years, reptiles;
for the last 200 million years, mammals;
for the last 150 million years, birds;
for the last 130 million years, flowers;
for the last 60 million years, the primates,
for the last 20 million years, the family Hominidae (great apes);
for the last 2.5 million years, the genus Homo (human predecessors);
for the last 200,000 years, anatomically modern humans.
Periodic extinctions have temporarily reduced diversity, eliminating:

2.4 billion years ago, many obligate anaerobes, in the oxygen catastrophe;
252 million years ago, the trilobites, in the Permian–Triassic extinction event;
66 million years ago, the pterosaurs and nonavian dinosaurs, in the Cretaceous–Paleogene extinction event.
Dates are approximate.

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