Fossils and its Types - Body, Molecular, Trace, Carbon Fossil

 

Fossils  and  Its Classification

Introduction 

Fossil

Fossils are the remains or traces of ancient life that have been preserved by natural processes, from spectacular skeletons to tiny seashells. Imprints, tracks and trails can also become fossilised, like dinosaur footprints or worm burrows. 

Fossilization

The preservation of animal or plant parts is called fossilisation. This process involves all the fossil's physical, chemical, and biological aspects. A hard petrified form is obtained from the rock that has the bones of animals or plants part impression.

Types of fossils 

1. Body Fossils

The first type, body fossils, are the fossilized remains of an animal or plant, like bones, shells, and leaves. These can be mould and cast fossils, like most of the fossilized dinosaur skeletons and big bones we see, replacement fossils, like petrified wood, or whole-body fossils – mammoths caught in the ice, or insects trapped in amber.

2. Molecular Fossils

Molecular fossils are often referred to as biomarkers or biosignatures and represent products of cellular biosynthesis that are incorporated into sediments and eventually into a rock. Many of these chemicals become altered in known ways and can be stable for billions of years.

3. Trace Fossils

Trace fossils are marks left by an animal or plant that has made an impression. These fossils include nests, burrows, footprints or any other markings of the animal’s time on the earth. The structure of the animal or plant remains as a mineral form. The colours of the minerals that replace the form can be dazzling. Sometimes they are made into art and jewellery.

4. Carbon Fossils

All living things contain an element i.e. carbon. When an organism dies and is buried in sediment, the materials that make the organism break down and eventually only the carbon remains. The thin layer of carbon left behind can show an organism’s delicate parts like leaves or plant e.g. fern fossil 300 million years old.

5. Pseudo fossils

Sometimes watery solutions of various minerals speed through the sediments and it takes the shape of some plant part or animal. Their study shows that they are neither plants nor animals. Such fossils are called pseudo fossils.

6. Amber fossil 

 Fossil resin from trees that has achieved a stable state after the loss of volatile constituents and chemical change after being in the ground, is called amber. It has been appreciated for its natural beauty and colour for a very long time. Although it is primarily used in jewellery as amber gemstone, it also has several medicinal uses.

7. Petrified fossils 

Petrified fossils result from permineralization, the replacement of once-living matter by minerals. Solutions containing silicates, carbonates, iron or other minerals seep into the gaps and spaces between the cells, first encasing the cells and eventually replacing the cells themselves. Over time, minerals entirely replace the organic material, creating a petrified fossil.

8. Mold and Cast  Fossil 

Fossil molds and casts preserve a three-dimensional impression of remains buried in sediment. The mineralized impression of the organism left in the sediment is called a mold. The mineralized sediment that fills the mold recreates the shape of the remains. This is called a cast.

There are two types of molds. They are:

External Mold:

It is a mold of the outside of the shell. Each time we break a shell or bone out of the rock, an external mold is left behind.

Internal Molds:

Molds of the underside of the shell may be left on the surface of rock that formed when sand or mud filled the inside of the shell.

9. Compression Fossil 

 A compression fossil is a fossil preserved in sedimentary rock that has undergone physical compression. While it is uncommon to find animals preserved as good compression fossils, it is very common to find plants preserved this way. The reason for this is that physical compression of the rock often leads to distortion of the fossil.

10. Impression fossils 

 Impression fossils are similar to compression fossils in that they are both two-dimensional, but these fossils are not remnants of the plant itself and do not contain organic material. Impression fossils essentially leave an imprint of the plant material in some fine-grained or soft sediment, such as clay or silt. Once the plant matter decays, the impression remains to be fossilized.

Conclusion 

Fossils are crucial evidence of evolution because they provide a direct window into Earth's past, revealing how life has changed over millions of years. By studying fossils, scientists can trace the development of species, identify extinct organisms, and understand the connections between ancient and modern life forms. Fossils demonstrate the gradual changes in anatomy, structure, and function, supporting the theory of evolution proposed by Charles Darwin. They also help establish timelines for evolutionary events and show how environmental changes influenced the survival and adaptation of species.