WEIT 2012 Chap2

WRITTEN IN THE ROCKS

What is a fossil?

A fossil is an animal or a plant which has been preserved by time. {co|not precise enough. You should give here a very precise description of what is a fossil.}--Pierre.brawand 15 mars 2012 à 17:22 (CET)

A fossil is really useful. Scientists consider them as a record, in the way that it gives to the scientists a lot of indications about the ancestors of species and about evolution.

How are fossils formed?

An animal or a plant can be fossilized only with very specific circumstances. First, they must find their way into the water, then sink to the bottom and get covered by sediments. After this, the hard parts of fossils become infiltrated or replaced by dissolved minerals to be then compressed into rock by the pressure of sediments piling up on top.

be more precise about the process of fossilization--Pierre.brawand 15 mars 2012 à 17:22 (CET)

Where do scientists find fossils?

Scientists must brave a lot of dangers to hope finding fossils. Finding them demands a lot of time, it's expensive and risked. Indeed, scientists must face diseases, political troubles and inhospitable places, where the fossils are usually found, such as the Sahara Desert. They need also a lot of luck to find the place where a fossil is. Furthermore, once the scientists have discovered them, they must then extract, prepare and describe them.
Fossils are found in the Sahara Desert, because in the time of the prehistory, there were a lot of lakes and swamps in this place, what facilitated the creation of fossils. To form a fossil, an organism needed some water, this is why a lot of fossils are found near oceans, lakes or rivers.

Why are fossils so important for Evolution?

"The story of life on earth is written in the rocks."
Thanks to fossils, scientists can understand the evolution of species and know how a common ancestor of a specific fossil looks like. Without them, we will only know relationships between species through similarities in form, development ans DNA sequence, but not when a species appeared on earth or which is its common ancestor Advances in sciences have provided and will provide precious insights from the past.

References

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