FOSSILISATION AS A PROCESS AND ITS SIGNIFICANCE IN INTERPRETATION OF EVOLUTIONARY EVENTS
The term fossilisation refers to the deposit of inorganic processes which allow the remains of a past living creature to be after its death. This word is derived from the Latin word meaning dug up. On the beginning of ancient Greeks it was used to describe different objects or materials found underneath the ground or found lying on the surface of the earth including mineral ores, rocks, stone implements and organic remains.
Fossils are formed when a living organism dies and the body or part of the body is preserved in a different way but usually by being buried rapidly in sediments. Burial prevents destruction of organisms by scavengers, bacteria or weathering. In most cases burial can occur in different places like on the bottom of the sea, in rivers or in Lakes. Shells bones, teeth, husk and skeleton are the only hard parts which are preserved usually and they are can survive even if subjected to traumas such as impact fracture, disintegration or dispersal caused by atmospheric phenomena . In some instances soft parts such as mammoths are also preserved but it is hard for them to survive because they are vulnerable to predation and decomposition.
The importance of fossils is in interpreting the evolutionary events, like in the case of dinosaurs. If it was not of fossils the generation of today would not even have a clue on how it use to look like. Fossilisation as a process can only take place when certain conditions are present. This process depends on the chemistry of an environment and on the biochemical make-up of the organisms. There are different processes through which fossils can be preserved:Pertrification is the crystallization of minerals inside cells. One of the best known forms of Pertrification is silicification, a process in which silica-fluids enter the plant’s cell and crystallize, making the cells appear to have turned to stone. Pertrification can also occur in animals when minerals such as calcite or silica fill the pores and cavities of fossil shells and bones. Carbonization plants are mostly fossilised through this process. The mobile oils in the plant’s organic matter are leached out and the remaining matter is reduced to a carbon film. Plants have an inner structure of rigid organic walls that maybe preserved in this manner, revealing the framework of the original cells. Animal soft tissue has a less rigid cellular structure and is rarely preserved through carbonisation. Recrystallization animal shells are composed of mineral aragonite, a form of calcium carbonate that breaks down over millions of years to form the more stable mineral calcite. This method of preservation destroys the microscopic details of the shell but does not change the overall shape.
Mummification may occur in hot arid climates which can dehydrate organisms before their soft tissue are fully decayed. The skin itself is preserved for only a short time but the impressions of the skin in the surrounding sediment turns to rock.There are other different methods for preserving but they all perform different functions. Everything which happened in the past is discovered through fossilisation and it is compared to the present evidence if such species still exist.
1. Wikipedia contributors, the free encyclopedia [internet] [cited 2006- May- 02] Available from: http://palaeo.gly.bris.ac.uk/communication/harrison/fossil.html
2. Wikipedia contributors, the free encyclopedia [internet] [cited 2006- May- 02] Available from: http://www.musei.unina.it/Paleontologia/eng/184.108.40.206.htm
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