What factors determine if animals and plants will form fossil?

The presence of high temperature and pressure, soil as a medium and also microbes are the factors that determine if animals and plants will form fossils.

Explanation:

As plants as well as animals dies in moist condition, and when buried inside the mud or silt. The soft tissues present starts degrading leaving behind the hard bones and also shells. Over the period of time various layers gets formed over it. As a result of high pressure and temperature fossils are formed. In case of animals the mineralized shell i. e. trilobite and ammonite form the fossils. It takes around 10,000 years for the formation of fossils the time period is minimum it may vary according to the species.