Theories of Evolution Essay Example

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Introduction

In general, the term ‘evolution’ can imply a drastic or gradual 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 evolution as a biological tool for change among species and consider fossil record as supportive of both evolution theories and also the other theories contrary to evolution.

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Evolution is the central unifying concept, a theory that successfully connects biology, palaeontology and other branches of science. Evolution is a gradual descent of organisms accompanied by changes that help the organisms to adjust and adapt to the surroundings. ‘Descent with modifications’ as Darwin contended implies changes in organisms in successive generations (Mayr, 1976). These changes are triggered by the derivation of new species and there is a change in the properties of populations of organisms and these properties tend to transcend the lifetime of any single individual. Newers pecies are modified versions of older species. Although, individual organisms do not biologically evolve,populations evolve when heritable genetic materials are transmitted from one generation to another. Biological evolution can range from very limited changes to drastic transformations on a large scale changing the entire special together and bringing in new forms. Evolution can thus be defined as inheritable changes in populations of species that are spread and transmitted over many generations (Zimmer, 2002). It is also more scientifically defined as changes in the frequency of alleles within a gene pool carried through different generations as understood in the Darwinian version of the theory(Dawkins, 1989). Evolution studies are supported by detecting changes in gene frequency within a population and the fact that the theory of evolution emphasizes on a common ancestor, only indicates that two or more species show successive heritable changes in populations since they are separated from each other as distinct forms (Allen and Briggs, 1989). Most popular definitions of evolution however highlight not the transmission of heritable traits and changes but the processes of diversity that has given rise to millions of species from the most primitive organisms. Here however we move on to the evidence for and against evolution theories and the role of fossil record in this context. Some researchers claim that the theory of evolution has been supported by four primary sources that serve as evidence (Zimmer, 2002; Allenand Briggs, 1989):

  1. The fossil record that tracks changes in early and primitive forms of life
  2. The anatomical and chemical similarities in the constitutions of different species.
  3. The genetic changes observed and recorded in several living organisms over several generations
  4. The geographical spread and distribution of species that seems to suggest a definite pattern, and

The Fossil Record

Fossils are buried in rock layers as indentations of dead plant and animal materials.

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