Example Biology Essay:The Fossil Record

Example Biology Essay: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 which have traitstransitional between different major groups of organisms. Fossils oftransitional forms actually give considerable evidence of species evolutionover time. However there is not enough evidence through fossil records toconclusively prove evolution, as there are still talks of 'missing links' asvery few and according to some, no transitional forms have been actuallydiscovered. The Fossil record data available to us is incomplete and inconclusiveat present.

During the late eighteenth and early nineteenth centuries,William Smith, a British Engineer observed different assemblages of fossilspreserved at different levels and different ages of rocks. These assemblagessucceeded one another in a regular and determinable order (cited in, Wikipedia,2004). This was further bolstered by the fact that rocks collected fromdifferent locations showed similar fossil formations according to the differenttimes they represented. Smith named this correlation of rock fossil data as theprinciple of faunal succession. The occurrence of faunal succession was one ofthe primary arguments of Darwin who used fossil evidence as supporting thetheory of evolution.

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Various modern approaches to the theory of evolution havebeen recently developed. Mayr claims that the theory of Punctuation forinstance has two basic points that

1. most or all evolutionary change occurs during speciationevents, and

2. most species usually enter a phase of total stasis afterthe end of the speciation process (which involves formation of new species).

Speciation thus involves transformation of species ingeological time (Erwin and Anstey, 1995). Formation of new species is explainedeither by phyletic gradualism or a gradual steady transformation of species byphyletic evolution highlighting the deficiency of the fossil records, or bysympatric saltational speciation that highlighted punctuational equilibria andbranching of species rather than transformation as lineages as the real explanationfor evolution (Mayr and Provine, 1998). Biologists like Gould and Eldredge havealso supported punctuation theories. Richard Dawkins on the other hand stresseson the principle of gene multiplication where genes as replicators seems to bethe focal point of defining evolution (Sterelny, 2001).

In quite an important paper Volkenstein (1987) suggeststhat there can be no contradiction between punctuated equilibrium and phyleticgradualism if synergetics and theory of information are incorporated within thetheory of evolution. Punctualism can be seen as phase transition maintainingthe directionality of evolution. Volkenstein argues that Punctualism, non-adaptationism and neutralism form the triad ofinternally connected features of evolution.

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