A fossil is the remains of an organism that lived long ago. These organisms can be plants or animals.
A fossil is the remains of an organism that lived long ago. These organisms can be plants or animals. Fossils can help us to better understand what life was like thousands, and even millions of years ago. Some fossils provide evidence of living things that have gone extinct, which means they can no longer be found alive anywhere on Earth today. In this lesson, we will examine 4 different types of fossils.
The first kind of fossil is a trace fossil. Imagine an animal steps in some mud and leaves a footprint. If that mud hardens and is not disturbed over a long period of time, it can turn into rock. This type of fossil is called a trace fossil because we can see a trace of part of the organism that left it. Trace fossils are not the organisms themselves, but rather evidence leftover from a plant or animal.
Another type of fossil is known as preserved remains. While rare, it is possible to find the body of an organism from a long time ago. For this to happen, something must keep the soft tissues of the body protected over thousands of years. Some examples of materials that might protect the remains of an organism are sap, tar, or even ice. Here is an example of a spider that may have become trapped in some sap. The sap hardened and protected the remains of the spider’s body so that it did not decompose over time.
A third type of fossil is known as a mold or cast. This type of fossil is formed when an organism is buried in layers of sand or mud but is not completely protected from the environment. Slowly, water and minerals seep into the ground and break down the living organism so that its remains are no longer there. However, the space that is leftover is still in the exact shape of the organism that was once there. This space is called a mold. Sometimes, the empty space is filled with new material that hardens and, when uncovered, can take on the shape of what the original organism once looked like. This type of model is known as a cast.
Finally, a fourth type of fossil is known as a stone fossil. Stone fossils are often mistaken for the leftover parts of living organisms. When the soft parts of a dead organism decays over time, all that may remain are teeth and bones. Gradually, minerals replace the bones that are left. The newly formed rock takes on the same shape and size as the original animal’s bones or teeth. Many of the fossils you see in museums are in fact stone fossils and not the actual bones from the dead organism.
Fossils take an extremely long time to form. They can be shells, bones, skin, fur, leaves, stone, or even footprints. Fossils form in many ways and can help us to better understand what life was like on Earth long before we were here.