As organisms are exposed to population pressure, successful variants accumulate across generations. Natural Selection is solely concerned with the preservation and accumulation of advantageous variants under the conditions to which each species is subjected.
Carbon dating and radioactive calculations are used to determine the age of fossils. Because all living things are made out of carbon, the relative age of fossils that formerly contained living animal or plant life can be determined by determining when the fossil was alive. When the sun's rays strike animals or plants and collide with nitrogen, Carbon 14, a radioisotope, is formed. The act of superimposing one object on top of another, especially so that they coincide, is known as superposition.
The geologic time scale serves as a record of the earth's key events and changes. This was established by scientists in order to keep track of the significant geographical events taking place on the planet. Relative dating was used to build the geologic time scale.
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