Evidence of Evolution as Seen in Comparative Morphology

Evidence of Evolution As Seen In Comparative Morphology

Introduction

Conclusive understanding of evolution in developed plants and animals relies on the relative studies on morphological composition of observable structural components. Scholars have tended to analyze the internal and external structures of varying body parts of relatively similar groups of organisms in order to classify them based on their ancestry. Evolutionists have noted that morphological observations account for the polygenetic lineages of organisms since evolution is a series of splits or speciation events. Evolutionary evidence asserts that information is contained within the morphology and the ancestry of the organism, verification that can be inferred to offer conclusive accounts of an organism's ancestral lineage, (Sastri, 2007 and Gingerich, 1984).

Theoretical Analysis of Comparative Morphology

Arising from the Greek word morpho meaning body forms comparative morphology can be described as the study of body forms and structures of major groups of organisms most notably vertebrates and flowering plants (Starr, 2007). Existent similarities in either internal or external body structure may be evidence of common ancestry, with the structures being referred to as homologous structures. Theoretically, comparative morphology is defined by two key concepts, which further offer clarification between comparative morphology and evolution. The concepts inlcude morphological divergence, which asserts that body parts acquired from a common ancestor are modified and specific to given lines of descent; i.e. different lines of descent attain different modification. Conversely, morphological convergence asserts that body parts that look alike were devoid of common ancestry but evolved independently in different lineages (Starr, 2007).

Comparative Morphology as Evidence of Evolution

The majority of scholars attest to the fact that comparative morphology is valid evidence of evolution since the existence of similarities in internal structures of body part(s) could be presented as evidences of common ancestry between any comparable groups of organisms (Marzke & Shackley, 1986). An exemplification of the five- toe limb can be noted as evidence for evolution since the limb has primarily evolved into different kinds based on their relative functions. This dominance is on the basis of continued use and structural demand for the particular limb. For example, in elephants the five-toed limb has evolved into a pillar like structure based on the organism's weight. In penguins it has evolved into flippers owing to the way penguins flip their wings (Starr, 2007).

A closer look at the differences in corresponding structures in terms of size, shape, or function within organisms reveals an inherent relationship, a proof of common ancestry. The structural composition of individual body parts in higher order animals for example, bone arrangement offers evidences to the evolution theory. The perpetuation of genes with the ability to function in similar ways across different lineages forms evidence of common ancestry. In animals, the genetic evidence is clear as studies indicate that embryos of different species have developed in similar ways for a number of years. This may however, be a justification for individuals opposing the concept of evolution who suppose that, if specific genes have guided the development of specific organisms, then the concept of evolution is invalid.

An explanation based on the theoretical predisposition of comparative morphology asserts that dominant changes across the years resulting from non uniform developmental rates may account for the difference. Notably, the variation seen in adult vertebrates results from mutations of genes that tend to control growth rates leading to non uniform growth in different patterns of development (Gingerich, 1984). Mutations have also been noted to accumulate the DNA used to enhance the divergence of species. The variation can be illustrated by the human genome where Begun (1997) estimates that 5% of human genome could affect the expression of certain genes in developing tissues further leading to variations that cumulatively causes differences within the species.

Comparatively, embryonic studies between varied species of vertebrates reveal a generally similar pattern of bone development, and tangible evidence of common ancestry. It is common knowledge that both plant and animal life constituted by multiple cells are formed by a fertilized egg. Therefore, the aspect in which different organisms tend to show similarities in morphologies during their embryonic stage is conclusive evidence of evolutionary relationship. Early embryos of vertebrates strongly resemble one another resulting from continuous inheritance of the same ancient plan for development.

Similarities at different stages of varied organism's development form evolutionary evidences. One illustration of changes occurring in the timing of development is the similarity in size of the skull bones of humans and the chimpanzees at the time of birth, (Begun, 1997). As the two develop in age, dramatic differences are observed. Starr (2007) asserts that for humans, the sizes of the bones of the face and the brain chamber increases as individuals grow from infancy to adulthood. However, for chimpanzees there is an imbalance as the facial bones grow faster comparative to the brain chamber bones. This results into the relatively dissimilar facial structures.

Morphological evidences based on biochemical similarities also attest to the theory of evolution. Protein comparisons form a primary defining factor as they form the basic constitution of genes. Since genes dictate the sequence of amino acids in protein, protein analyses have provided evidences of the existence of similarities between species. Rhesus monkeys and chimpanzees have similarities in amino acid sequencing processes, and strong evidence of common ancestry (Begun,

...