Shells and Fossils
Click the Play Button to Listen to the Text
Most of the “seashells” that we see on the beach are the empty shells of mollusks who have died. The empty shells that people like to collect play an important role in nature. For example, there are various crabs that are incapable of making their own shells that use empty shells as a mobile home and refuge.
Naturally, over time, the shells decompose, return to the ocean floor, and enrich it with calcium. Calcium is essential to young mollusks and a range of sea animals in order to grow, develop skeletons, and facilitate healthy metabolism. It is therefore clear that leaving seashells in their natural place is very important, and it is possible to understand the prohibition against collecting them from beaches and selling them.
The phylum Mollusca existed in oceans 550 million years ago. It is the second largest phylum in nature and includes a huge range of species. Many of them have a shell from the moment they hatch. The shell protects the mollusk and continues to grow with it throughout its life. There are three primary classes in the Mollusca phylum.
Snails - Most of them live in water, with a few living in freshwater or on dry land. Most have a spiral-shaped shell. Land snails are called terrestrial mollusks.
Bivalvia - These live in the ocean or freshwater and have a double shell with two equal parts.
Cephalopods - These live in the sea and include the octopus, squid, and nautilus.
Fossils are testimony to the past lives of animals and plants. The scientific field that studies fossils is a branch within geology that is called paleontology.
Most fossils are the remains of animals or plants that were buried on the ocean floor, and the hardened impression of their body was preserved, fully or partially, in the rock. There are thousands of types of fossils in the world that were formed by different processes over millions of years.
We can learn from them about animals and plants that lived in different periods, and they help geologists understand the ages of different layers of the Earth.
In this display window, there are a few types of fossils that were created by different processes.
Trace fossil - this was created by the external side of the animal, which was impressed into the soft sea floor or lake floor millions of years ago. Its shape is essentially a negative of the shell.
Mold and cast fossil - this shows the complete form of the shell.
A fossil is usually created from the hardened parts of the organism, such as the shells of mollusks, or the bones of vertebrates. Mold and cast fossils show the whole or partial shape of the shell or bone.
Impression fossil - A good example of an impression fossil is the white stone on which a fern leaf was impressed. The fossil was created when the fern rested on a rock, and over time, oxides from the rock penetrated the leaves. The oxides broke down the organic material of the plant very slowly, until a precise impression of the fern leaf was left on the face of the rock.