The older the fossil, the more fluoride it contains so that the relative ages can be established. It is not possible to decide absolute ages using this method since the concentration of fluorine in ground water varies from place to place and from time to time.
There are many gaps in the fossil record because organisms have not been preserved. There are also a very small proportion of the fossils that do exist have actually been discovered. Some are buried too deep in the ground to be found or they are in inaccessible places. Others may have been inadvertently destroyed by human activity like agriculture or industry.
The dead organism must not decay - Soft parts of organisms decay because scavengers and decomposers eat them. If they can be kept away from the dead organism, it may become a fossil. Decay can be prevented by having unsuitable conditions for decomposers.
Fossils are the remains of living things. Artefacts are the objects that have been deliberately made by humans.
They are important because each radioactive element decays at a constant rate which is unique to that element. These rates of decay or known so it you can measure the proportion of parent and daughter isotopes in rocks, you can calculate when the rocks were formed.
They are of great value in this correlation work because they are widely distributed making relative dating of strata more precise.
The dead organism needs to be buried quickly - As soon as organism dies, it is covered in sediment. On land, it can be buried by sand or volcanic ash. In oceans and lakes, it can be covered by sand and mud which are being carried by rivers or currents. A quick burial usually involves the dead organism being covered by sediments.
A. Yes. Patterns in the distributions of fossils and living species are useful evidence of evolution.
A. Yes. Patterns in the distributions of fossils and living species are useful evidence of evolution.