Evolution


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Agenda Spring 2001
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Geologic Time Scales

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Time Periods In Evolution

Millions of years ago (mya)

 

Major Events in the History of Life on Earth

Millions of years ago (mya)

Precambrian

4,600-544

     

Hadean Eon

4,600-3,800

 

The Earth formed as a solid planet

4,600

Cryptozoic Eon

3,800-544

 

Formation of atmosphere and oceans

3,800

Archaean Era

3,800-2,500

 

Life (the first bacteria) formed

3,500

Proterozoic Era

2,500-544

 

Oxygen began to build up in atmosphere

2,500

Vendian Period

650-544

 

First cell with a nucleus (called "eukaryotes")

1,400

Phanerozoic Eon

544-Today

 

First organism with many cells (= multicellular algae)

1,000

Paleozoic Era

544-245

 

First soft-bodied animals (like jellyfish and simple worms)

680

Cambrian Period

544-505

 

First animals with hard shells

(= marine invertebrates)

540

Ordovician Period

505-440

 

First animal with a backbone, vertebrates (= a jawless fish)

510

Silurian Period

440-410

 

First land plants, (like ferns, NOT flowering plants!)

440

Devonian Period

410-360

 

First land animals (= insects)

400

Carboniferous Period

360-286

 

First amphibians, (like frogs)

360

Mississippian Epoch

360-325

 

First reptiles, (like lizards)

300

Pennsylvanian Epoch

325-286

 

First dinosaurs

235

Perimian Period

286-245

     

Mesozoic Era

245 to 65

     

Triassic Period

248-213

 

First mammals, (small rat-like insect-eaters)

225

Jurassic Period

213-144

 

First birds

150

Cretaceous Period

144-65

 

First flowering plants

140

Cenozoic Era

65-Today

     

Tertiary Period

65-1.8

 

Mass extinction of many kinds of life, including dinosaurs

65

Paleocene Epoch

65-55

 

First primates (similar to tree shrews)

65

Eocene Epoch

55-40

 

Primative Apes appear, Elephant, horse, and camel develop.

40

Oligocene Epoch

40-26

 

First monkeys

35

Miocene Epoch

26-14

 

Grasslands spread

26

Pliocene Epoch

14-1.75

 

Modern sea life appear.

14

Quaternary Period

1.8-Today

 

The beginning of human-like animals (hominids)

4

Pleistocene Epoch

1.75-0.025

 

The Ice Ages being, mammals dominate Earth

1.75

Holocene (Recent) Epoch

0.025-Today

 

Modern humans (Homo sapiens sapiens)

0.05

  • The Geologic Time scale provides a relative measure of time. · The Geologic Time scale is based on the fossil record.



 


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