A Fossil - The preserved remains of a once living organism, a body fossil is usually the skeletal remains or the "hard parts" of a fossil. Although some conditions allow for the soft part to also be preserved. Another type of fossil is a trace fossil, the tracks, trails and burrows of past organisms.
Some factors affect fossilisation, these include:
Orginal Composition - This is where a fossil is made of calcite or aragonite, these can be easily altered. Whereas silca fossils (e.g. Radiolaria) can be preserved unaltered
Energy Levels - High energy…