Palaeontology : It is the study of fossils or the remains or organisms of past geological age. This includes palaeobotany (dealing with botanical fossils) and palaeozoology (dealing with zoological fossils).
Fossils : Fossils are preserved remains of animals, plants or their parts found in the various layers of the earth’s crust or rocks. The word fossil (Latin-Fossilium-something dug out) means anything dug out of the earth. The importance of fossils was first recognised by the Leonardo da Vinci in 1800.
Types of Fossils : Generally fossils are found in three different forms :
1. The actual organic remains.
2. The petrified fossils.
3. Moulds and casts.
1. Actual Organic Remains : After the death of the animals the original hard parts of the animals such as bones, teeth, shells are preserved in salt water. They are buried and covered with sediments e.g., in Siberia 50 huge fossil elephants-Wooly Mammoths which lived 20,000 years ago were preserved in ice.
2. The Petrified Fossils : The replacement of organic matter by minerals is called petrification. In this type of animal fossils, parts of the body or the whole body itself are replaced by minerals like silica, calcium carbonate, iron pyrites, sulphur, dolomite, gypsum etc. The petrification is classified into the following types:
(i) Silicification : Original matter of the dead body is replaced by silica e.g., fossil sponges.
(ii) Phyritization : Original matter of the animal’s body is replaced by iron pyrites.
(iii) Carbonization : This is another kind of fossilisation where carbon compounds are deposited in the place of original material. e.g., chitinous skeletal parts.
(iv) Dolomitization : It is the replacement of original material by double carbonate of calcium and magnesium with magnesium predominating its composition. Dolomitized fossils occur on the sea floor. Delicate parts cannot be fossilized by this method.
3. Moulds and Casts : When animals and plants die, the disintegration of their body might leave indelible impressions on the soft mud which later becomes hardened into stones. Such impressions are called moulds. The moulds can give information about the size, shape and the nature of the parts of the prehistoric animals. Casts are similar to moulds. Here the disintegrated animals may leave cavities. Casts are formed when by these cavities are filled up by hard minerals.
Other methods of fossilization are preservation of foot prints or trails, preservation of body such as in resins and ambers, or preservation in ice etc.
Determination of Age of Fossils : To get the idea of evolution, it is necessary to find out the age of fossils. This study is called dating of fossils or determination the age of fossils. This can be studied by Radioactive Clock method, Radioactive Carbon dating, Potassium Argon method, Lead Uranium method etc.
Importance of Fossils
1. Fossils contribute a lot to know about the ancient earth’s geography, and about the prehistoric life.
2. The presence of land bridges between certain continents is understood by fossil records.
3. Fossils tell about the age of the earth.
4. Fossils give an indication of connection between certain groups of animals e.g., Archaeopteryx tells the relationship between reptiles and birds.
5. Fossil records are very helpful in assessing the climatic.
Shopping Cart
