Geology solar system

The History Of Life
Pre-cambrian (4600mya-540mya)

During this first period, life first appeared on Earth with a single celled bacteria which sometimes built pillow like colonies called stromatolites.  Later in the period primitive multicellular life appeared e.g. Jelly fish

Cambrian Period (540mya-490mya)

Evolution accelerated suddenly at the start of this period and complex life forms suchas trilobites which were the first creatures to see their world.  A giant shrimp called Anomalocaris was their main predator.

Ordovician Period (490mya-455mya)

Sea lillies first appeared during this period along with very often very large nautiloids closely related to modern squids which were the main predators of the time and trilobites were their main diet.  There was still no life on land.

Silurian Period (445mya-415mya)

In the sea, fish appeared for the first time, although most lacked proper jaws.  The land became colonised by primative plants for the first time during this period.  The main kind was called Cooksonia and was a few metres high.

Devonian Period (415mya-360mya)

Fish greatly diversified during this peropf and sharks appeared for the first time.  On land ther first small trees appeared and animal life, especially insects, started to become abundant.

Carboniferous Period (360mya-300mya)

During this period, there were dense forests of primitive looking trees over 40m tall and inhabited by giant insects and large predatory amphibians.

Permian Period (300mya-250mya)

Mammal like re

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second part to the history of life

The History Of Life

Permian Period (300mya-250mya)

Mammal like reptiles called therapsids dominated the land during this period and included snail backed forms.  They were almost entirely wiped out by a massive extinction event at the end of the period along with 95% of other species.

Triassic Period (250mya-200mya)

The permian extinction allowed true reptiles to evolve into many different forms during this period and they became the main predators in the sea and air as well as on land.  The first dinosaurs appeared towards the end of this period.

Jurassic Period (200mya-145mya)

During this period dinosaurs diversified into many different forms such as Stegosaurus and Brachiosaurus and dominated life on land.

Cretaceous Period (145mya- 65mya)

Dinosaurs continued to be very successful during this period with the appearence of large predatory forms such as Tyrannosaurus but at the end of the period they were wiped out possibly by meteorite impact.

Palaeogene Period (65mya-22mya)

The extinction of the end of the Cretaceous period allowed mammals to evolve into many different forms both on land and in the sea.  Birds were also very successful during this period dominating the skies.

Neogene Period (25mya-0mya)

Modern man first appeared towards the end of this period and spread over the World during the Ice Age.  In Northern Europe mammoths were a major source of food.

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