What is a fossil and how are they formed ?

What is Fossil

The word Fossil is simply known as the physical evidence of the previous life of a period of time prior to recorded human history. This prehistoric evidence includes the fossilized remains of living organisms and impressions of their physical form, and marks/traces created in the sediment by their activities.

For Example: Ancient Fossil groups such as the dinosaurs, ammonites and trilobites.

fossil foot prints

How do Fossils Forms

The formation of fossils also known as fossilization as it happens very rarely. Here the plant or animal continually preserved from the time of its death until discovery in case of they didn’t decay completely, like the hard parts and bones left behind.

The heat &  pressure from being buried in sediment can sometimes cause the tissues of organisms  including plant leaves and the soft body parts of fish, reptiles and marine invertebrates to release hydrogen and oxygen, leaving behind a residue of carbon. This  process is termed as carbonization, or distillation. Carbonization yields a detailed carbon impression of the dead organism in sedimentary rock. Fossilization also called permineralization or petrification. Minerals fill the cellular Spaces and crystalize. The shape of the original plant or rock is preserved as rock. Sometimes the original material is dissolved away and leaving the structure. But, none of the organic material remains. Fossils are also formed by volcanic ash, peat bags and paraffin deposits.

fossil head

Types of Fossils

  • Actual remains

The body of an organism, with all the parts intact. Usually preserved in ice, amber, or tar.

  • Petrified wood

When minerals replace wood or stone to create either petrified wood or a mineralized fossil.

  • Fossil fuels

Fuels formed by the remains of dead plants and animals.

  • Cast fossils

When minerals fill in the hollows of an animal track, a mollusk shell, or another part of an organism.

  • Mold (imprint) fossils

When a leaf, feather, bone or even a body of an organism leaves a trace in the sediment, which hardens and turns into rock.


types of fossils


  • Fossils are one of the best evidence of evolution(means shape) which remains of living organisms from the past.
  • It helps to find how organisms are changed for through the time.
  • Used to compare anatomy
  • Fossils helps to reconstruct the patterns based on the history of life.


  • DNA is unobtainable from fossils, and comparing with living organisms is difficult to make.
  • DNA is more accurate but limited to living organisms. You can’t get DNA out of a fossil.


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