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The geologican time calendar - Referat

Perhaps you know that our earth isn't very young . Almost she's about 4,6 billion
years old. At this time the earth crust was still liquid. This time is called Precambria.
It persists till about 570 million years before our time. So it's the most longest era of the geologic calendar.
The next time is the Paleozoic era. It persists about 320 million years and it is partitionated in 6 periods:
Cambria:(60million years): The oxygencontent of the air increased. First oxygen dependet organisms. In the end: simple organisms like worms

Ordovician(75 Million years): Invertebrate marine animals and primitive type of fish.

Silurian(30 million years): On the dry land: Scorpions millipedes
In the water: First fish with jaws

Devonian(50million years):.
In the end of the devonian the shores were settled by amhpibians

Carbonifereus(65 million years): Exuberant swamp forest vegetation
In the sea: Bones-and-gristle-fish like sharks

Permian(60million years): The first and only time in the history the hole cotinents were united in one giant continent called Pangaea. because the two great continents Euramerica and Gondwanaland collided.
Cryptogams like ferns withdrew in favour of seed plants.
The reptiles made some great evolutions

In the end of the Permian there was probably the most devastating catastrophe in the worlds history:
The sciencist Robert Berner found out that in the end of the perm there were much carbon maturing in the seas. After some examinations he found out that some
scenarios probably were getting together: Great sediments of the instable
chemical compound Methanhydrate on the seafloor became gaseous and leaked in the atmosphere. Also some volcanos in Siberia were active. Perhabs there was also an astronomic actuator like the strike of an asteroid which made the Methanhydrate instable,and let the volcanos erupt. Also he would have killed many animals and their rotting bodys also would have generated carbon.
After this 90% of all seacreatures were killed, completly extincted were for example the Trilobites, a kind of crayfish. Also 70% % of all Land creatures died but they regenerated quickly
In the end the carbon cyrculation had to organize completly new.

Althought very much animals died the fauna regenerated relative quickly
After the faune regenerated a new era began:

The mesozoic.It persists about 180million years and it's partitionated in 3 periods:
Triassic:(45million years): In the sea: Ichtyosaur. On the dry land: First dinosaurs
The giant Continent Pangäa broke
up and built the two Continent Laurasia which was put together of most of the continents wich are today on the northern Hemisphere: europ, north americ and asia
and the continent Gondwana wich was put together of south america, Africa, antarctica, austrailia and the subcontinent India.

I thing the next periods name you have already heard because its part of the name of a film:
Jurassic (65 million years): the jurassic was the evolutionary top of the reptilles.
Also here were the first mammals, they were predators and had the size of rats.

Cretaceous(70 million years). Here there was again a devastating catastrophe,
but this one wasn't as devasting as the first I were talking about:
The most popular explication is that a big asteroid struck on the earth.
But this theory isn't disproven or proven.

The next era is called kenozoic era it persist from 65 million years before us till today
It consists of the Tertiary (a bit more than 63 million years)and the Quartenary.
The tertiary (and generally the kenozoic era) was the age of the mammals.
A great variety appeared. Among others, predators, hoofed mammals and our direct ancestors the primacies.

Quartenary(for about 2 million years) the quartenary is the period where the evolution of the humans transpired. During the ice ages the humans sattled on all continents except the antarctica. They made some great evolutionatry steps and before 200000 years they were educed to the second most educed animal the homo sapiens.
And today's people are called "homo sapiens sapiens".

Dieses Referat wurde eingesandt vom User: Major_Milford

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