The Fossil Record and Theories of Evolution.
In general, the term 'evolution' can imply a drastic orgradual change from a very broad perspective. Life on earth, the universe,galaxies, as also the earth in general have evolved through millions of years.In this essay we consider only one aspect of evolution emphasizing on evolutionas a biological tool for change among species and consider fossil record assupportive of both evolution theories and also the other theories contrary toevolution. Evolution is the central unifying concept, a theory thatsuccessfully connects biology, paleontology and other branches of science.Evolution is a gradual descent of organisms accompanied by ...view middle of the document...
Most popular definitions ofevolution however highlight not the transmission of heritable traits andchanges but the processes of diversity that has given rise to millions ofspecies from the most primitive organisms. Here however we move on to theevidence for and against evolution theories and the role of fossil record inthis context. Some researchers claim that the theory of evolution has beensupported by four primary sources that serve as evidence (Zimmer, 2002; Allenand Briggs, 1989):
1. The fossil record that tracks changes in early andprimitive forms of life
2. The anatomical and chemical similarities in theconstitutions of different species.
3. The genetic changes observed and recorded in severalliving organisms over several generations
4. The geographical spread and distribution of species thatseems to suggest a definite pattern, and
The Fossil Record
Fossils are buried in rock layers as indentations of dead plantand animal materials. The totality of these artifacts and their impressions onthe rock formations is considered a fossil record. Fossil record as we havebriefly mentioned is the primary source of evidence supporting the theory ofevolution and the gaps in these records ironically also forms the bone ofcontention taken up by anti-evolution theorists. Fossil records are used byscientists to understand the process of evolution in general, and thesubsequent changes in several species at several times of the earth's existence(Donovan and Paul, 1998).
The Fossil Record seems to provide an important clue to thechanges in primitive and even now extinct species and this definitely helps usto frame a conceptual graph on how evolution has taken shape. Fossil and rockrecord forms the primary source of evidence collected by scientists for nearly400 years and the consequent database obtained is mainly observational. Thefossil record among all other evidence gives a large database of documentedchanges in past life on earth. The use of Fossil record to study life forms onearth dates back to pre-Darwinian times and the changes in life forms could bestudied from a sequence of layers of sedimentary rocks and fossils of differentgroups of species were found in each of these successive layers (SA, 1982).Sedimentary rocks are found widely across the earth's surface and are formedwhen small particles of sand, mud or gravel, shell or other materials witheredoff by water or wind accumulates in seabeds and oceans. As these sediments pileup they bury shells, leaves, bones, and parts of living organisms. Layers ofsediments are thus formed for every large period of time and all these layersbecome subsequently cemented to each other to become different layers of sandstone,limestone, shale and so on. Within these layers of sedimentary rocks the plantand animal remains become buried as fossils and are later revealed as fossilrecords (Allen and Briggs, 1989). From these fossil records several specieshave been identified, some of which are extinct and some of...