Scientific Methods

Friday, May 05, 2006


Fossilization is the process of change of matters into fossils. Fossils are the remains of animals, plants and organisms. They are many types of fossils which occur as result of different types of fossilization process. Fossil come in many different ways. They are different types of fossils and fossilization process fossils Each type of fossil is occurs as a results of different fossilization process and each tells scientist something about material conserve. Fossils consist of traces of remains of organism and mark left behind the organism while it was alive. E.g. footprint, trackways, bites marks and dwelling burrows. Fossilization is rare occurrence because most of the components of living things tend to decompose. Organism to be fossilized, the remains needs to be covered by sediments.

The term fossilization does not only refer to the remains of organism but also to the impressions in rock and traits form by organism when they are alive. Fossils are formed when living organism dies and the part of the body are kept safe. Burial prevents the destruction of organism by scavenger, bacteria or weathering and erosion. It is also important because oxygen is no longer available to bacteria that cause the decay. Fossilization favours the following organism: big organism with hard body parts, organisms that were widespread and organism that lived for a long time. It favours these because it is impossible to find the following: small fossils, soft bodied organism living in small areas that did not live for a long time, either because they become extinct or because they evolved quickly. Geological process such as erosion destroys many fossils.

Fossilization process start when living thing dies, flow down a river and lodges on a sandbar. The bone may get covered by mud or sand but the tissue and skin decomposed. In drier areas, animals may fall into a crack and be quickly covered by wind blown sand. Once burial has occurred the remaining process of fossilization can continue. During the period of some hundreds millions years sediments built up over the buried remains and the pressure drives water out and converts the sediments to rock.
During the life time of rock, water sort through it dissolves some minerals and deposit them at the other sites, and deposits different minerals at the original site of the fossil thus cause the fossil remains themselves become converted into different types of rock
The process of carbonization occurred in the process of fossilization, plant leaves, and some body parts of fish, and reptiles decompose going behind only the carbon. This carbon creates the idea in the rock giving the great details of fossil. Plants are commonly fossilised through carbonisation

Fossils are the main sources of information on the evolution. Without the information provide by fossil, we can not have no direct knowledge of timing of biological events such as the following: origin of life, the development of skeletons, the colonisation of the land, the appearance of mammals and the flowering plants, the development of flight and the major episode of extinction.

Fossils are the main source of information because it gives the history development and the evolutionary relationships of Morden flora and fauna. It also gives the knowledge and characteristics of extinct organism such as dinosaurs

Linette Netshiheni
CSIR Pretoria
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The mollusks constitute one of the largest phyla of animals, both in numbers of living species and in numbers of individuals. All mollusks have a soft body, which is protected by a hard, calcium- containing shell. Mollusks are triplobastic (ovum which has three primary germ layers-ectoderm (outer), mesoderm (middle) and endoderm (inner layer) protostomes. A significant characteristic of mollusks is their possession of a coelom, a fluid-filled cavity that develops within the mesoderm. The coelom functions as a hydrostatic skeleton which also provides space within which the internal organs can be suspended by the mesenteries. The body cavity is filled with blood. Mollusks have a mantle (fold of the outer lining of the shell and a muscular foot that is used for motion-movement). Many mollusks mantle produce a calcium carbonate-external shell and their gills extracts oxygen from water (1).

Phylum Mollusca are divided into different classes which have different types of shells:-

Class Gastropoda

Most of the approximately 40,000 living species of gastropods have shells, however there are quite a few groups that have either reduced or internal shells, or no shell at all. Although most Gastropods are marine, there are numerous forms in both freshwater and terrestrial environments. Most members have a shell which is in one piece and typically coiled or spiralled which usually opens on the right side (2). Some species have an operculum which operates as a trapdoor in order to close the shell.

Class Pelecypoda (Bivalvia )

They have two part shells with both parts being less or more symmetrical. The class include scallops, clams, oysters and mussels. Their shells are composed of calcium carbonate and the shells are very strong. In some bivalves the shell is made up of calcium carbonate known as aragonite which is not very strong (3).

Class Cephalopoda

This class includes species like squid, octopus and cuttlefish. Their shell is either internalized or is absent. The cuttlefish is the only modern shelled cephalopod. It occupies only the outermost portion of its elaborate and beautiful shell, the rest of which serves as a flotation chamber. In the squid and its relative, the cuttlefish, the shell has become an internal stiffening support, and the octopus does not have a shell entirely (4).

Class Monoplacophora

They have a single, flat, rounded bilateral shell which resembles chitons. Their shells are often thin and fragile and their shell apex is forward (5).

Class Polyplacophora

This class include the chitons which have seven or eight dorsal shell plates embedded in the tough muscular girdle that surrounds its body. Their calcareous armour shell that they carry dorsally acts as a protective measure. Their shell is made up of aragonite and colored (6).

Class Scaphopoda

They are also called the tusk shells because their shell is openly curved plan spiral tubular shell which opens at both sides and the shell resembles an elephant tusk. They have tapered, tubular shells that open at both ends (7).


1.Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 3:39 PTA [cited 2006 May 4]. Available from:

2.Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 3, 20:07 PTA [cited 2006 May 4]. Available from:

3.Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 3, 19:00 PTA [cited 2006 May 4]. Available from:

4.Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 03: 04:57 PTA [cited 2006 May 4]. Available from:

5.Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 22, 20:03 PTA [cited 2006 May 4]. Available from:

6.Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 04, 15:32 PTA [cited 2006 May 4]. Available from:

7.Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 23, 12:22 PTA [cited 2006 May 4]. Available from:

Lethabo Mosomane
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