1: Introduction

Age of the universe: 10-16 billion yearsAge of the solar system: 4.6 billion yearsAge of earth: 4.5 billion yearsAge of life: 3.5 billion yearsAge of eukaryotes: 1.8 billion yearsAge of multicellulars: 900 million yearsAge of chordates: 500 million yearsAge of mammals: 240 million yearsAge of primates: 60 million yearsAge of apes: 30 million yearsAge of genus Homo: 2.5 million yearsAge of Homo sapiens: 100,000 yearsWritten history: ~5,000 years

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solar system

oldest known rock (possibly with organic carbon)

nothing was living during the Hadean

earth

bacteria

eukaryotes

multicellular organisms

chordates

end of dinosaurs

The very beginning: -4500 millions years ago (mya).

The period between the creation of the solar system, and our time is divided in two:

(1)Precambrian Time (4.5 to 543 mya).(2)Phanerozoic Eon (543 mya to present).

http://www.ucmp.berkeley.edu/exhibit/geology.html

Hadean time:

•4.5 to 3.8 billion years ago.

•This is not a geological period as such. No rocks on the Earth are this old - except for meteorites.

• During Hadean time, the Solar System was forming, probably within a large cloud of gas and dust around the sun.

Oldest stones: zircon crystal 4.4 billion years

The boundary between the two eons (Hadean and Archaean) is defined because rocks appeared and with them - fossils

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oldest known rock (possibly with organic carbon)

Archaean time

•3.8 to 2.5 billion years ago

•The atmosphere was reducing, composed of methane, ammonia, and other gases which would be toxic to most life on our planet today.

•Earth's crust cooled down enough that rocks and continental plates began to form.

It was early in the Archaean that life first appeared on Earth.

Our oldest fossils date back to roughly 3.5 billion years ago, and consist of bacteria microfossils.

In fact, all life forms during the more than one billion years of the Archaean were bacterial.

Spheroids representing bacteria microfossils (1.8 to 3 billion years ago). Hoyt Lakes Mine (USA).

These microfossils are found within Banded Iron Formation (BIF).

Spherical objects, identified as microfossils and named Isuasphaera isua (Pflug), were reported in 1978 from Greenland stones 3.7-3.8Ga old.

However the nature of these objects is questioned.

gigaannum, usual symbol Ga, is a unit of time equal to 109 years.

Extensive banded iron formations (BIF's) on the western shores of Lake Superior, indicate that photosynthesis was occurring and oxygen was being produced

Modern stromatolites Australia

stromatolites

Pre-cambrian stromatolites Australia 1.6 billion years old

Pre-cambrian stromatolites South Africa 3.5 Ga

The boundary between the two eons (Archaean and Proterozoic) is defines because oxygen appeared

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•With the beginning of the Middle Proterozoic comes the first evidence of oxygen build-up in the atmosphere.

•This global catastrophe spelled doom for many bacterial groups, but made possible the explosion of eukaryotic forms. These include multicellular algae, and toward the end of the Proterozoic, the first animals.

Proterozoic = the O2 pollution

Proterozoic Era: The first Eukaryotes

(1.6 - 2.1 Ga)

The exact origin of eukaryotes is unknown. But few signs allow to differentiate Eukaryotes fossils from bacteria

The size of the cell.

The presence of tetrades (4 cells together)

Grypania spiralis was a coiled, spaghetti-like organism up to half a

meter in length found in ~1.3 Ga shales from Montana, China, and

India.

Shales = צפחה

Proterozoic Era: The first Eukaryotes

(1.6 - 2.1 Ga)

The exact origin of eukaryotes is unknown. But few signs allow to differentiate Eukaryotes fossils from bacteria

The size of the cell.

The presence of tetrads (4 cells together)

Tetrad: ~ 555-590 Ma China.

A widely distributed group of soft-bodied marine organisms

(First discovered in 1868 but only seriously considered in 1957 !)

Proterozoic Era: the first animals (635 to 542 Ma)

Dickinsonia (south Australia and north Russia)

Cyclomedusa radiata, (Australia)

Proterozoic Era: the first animals (635 to 542 Ma)

Proterozoic Era: the first multicellular algae

Doushantuophyton 555-590 Ma China.

The boundary between the two eons (Proterozoic and Phanerozoic) is defined because animal fossils appeared

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The presence of fossils in the “Primordial Strata” was noted as early as the mid 19th century

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Phanerozoic

Cambrian explosion

The Cambrian explosion (543-490 MYA)

Almost every metazoan phylum with hard parts, and many that lack hard parts, made its first appearance in the Cambrian.

Anomalocaris: A giant predator of the Cambrian (some specimens grew up to 2 metres)

Hallucigenia: wormlike 0.5 to 3 cm-long animal.

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Phanerozoic

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Paleozoic

Cambrian explosion

First land plant

First jaw fish

First land vertebrateFirst seed plantFirst insects

Mass extinction

First reptiles

•At the other end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species. The causes of both these events are still not fully understood and the subject is still under much research and controversy.

•Roughly halfway in between, animals, fungi, and plants alike colonized the land, the insects took to the air.

5 mass extinctions

Paleozoic Mesozoic

Permian-Triassic crisis

Foraminifera (plankton)

97%

Radiolaria (plankton)

99%

Antozoa (sea anemones, corals, etc.)

96%

Bryozoans 79%

Brachiopods 96%

Bivalves 59%

Gastropods (snails)

98%

Ammonites (cephalopods)

97%

Crinoids (echinoderms)

98%

Blastoids(echinoderms)

100%

Trilobites 100%

Eurypterids ("sea scorpions")

100%

Ostracods(small crustaceans)

59%

Graptolites 100%

The boundary between the two eons (Paleozoic and Mesozoic) is defined because there was a big change in fauna (e.g., Dinosaurs)

End of dinosaurs

Cambrian explosion

First land plant

First jaw fish

First land vertebrateFirst seed plantFirst insects

Mass extinction

First reptiles

First dinosaurs

First birdsFirst flowering plants

Mammalian reptiles

First placental mammal

Mesozoic Era

•248 to 65 millions years ago.

•The Mesozoic is divided into three time periods: the Triassic, the Jurassic, and the Cretaceous

•Mesozoic means "middle life", and is the time during which the world fauna changed drastically from that which had been seen in the Paleozoic.

•Dinosaurs, which are perhaps the most popular organisms of the Mesozoic, evolved in the Triassic, but were not very diverse until the Jurassic.

Except for birds, dinosaurs became extinct at the end of the Cretaceous. Some of the last dinosaurs to have lived are found in the late Cretaceous deposits of Montana in the United States.

The boundary between the two eons (Mesozoic and Cenozoic) is defined because there was a big change in fauna (e.g., non avian Dinosaurs extinct, Mammals explosion)

Cenozoic

Cenozoic Era:

65 millions years ago to the present

The Cenozoic is sometimes called the Age of Mammals, because the largest land animals are mammals since that time.

The term “the Age of Mammals, is a misnomer for several reasons:

First, the history of mammals began long before the Cenozoic began.

Second, the diversity of life during the Cenozoic is far wider than mammals.

The Cenozoic could have been called:the "Age of Flowering Plants" or the "Age of Insects" or the "Age of Teleost Fish" or the "Age of Birds"

just as accurately.

If Earth was created 24 hours ago,

Life appeared at 02:45.

Eukaryotes at 16:00.

Humans at 23:59:59