Theory of evolution

The contemporary theory of evolution, according to Nardo (2009), was developed by a proletarian English naturalist known as Charles Darwin, in the 19th century. Darwin proposed that all living things evolved slowly from a common ancestor through natural selection over billions of years. The principle behind this theory, as illustrated by Scotney (2009), was that individuals passed on their best adapted character traits to their offspring. This theory proposed that random mutations on the gene occur over time within the organisms genetic code leading to development of beneficial character traits that are retained since they support survival. Over time, as asserted by All About Science (2010), these beneficial character traits accumulate and transform individuals into a species completely different from their ancestors. Darwins theory presumes that life developed from non-living things and stress that organisms evolve naturally from simple ancestors over time. Ancient Greek philosophers hypothesized the development of life from non-living things as well as the evolutionary descent of man and other living organisms from a certain ancestor. Darwin contributed to this philosophy by bringing in a plausible mechanism known as natural selection. Natural selection according to Darwin acts to accumulate and retain minor beneficial genetic mutations. Darwin claims that if a member of a certain species develops a certain character trait that helps it to survive, that trait will be inherited by its offspring and passed on to their offspring. According to natural selection members of a particular species that do not have the advantageous character traits would eventually die out, leaving on the members of the species that have the advantageous traits. Natural selection allows for the preservation of beneficial character traits thus allowing species to struggle better in the wild. This can better be explained by looking at the work breeders have done over the centuries. By selecting the good looking animals, breeders are able to eliminate undesirable traits over time while retaining the desirable ones.

Evolution evidence can also be obtained from categorizing the similarities between organisms living on distant locations. Biogeography was one of the central themes of Darwins reason when he summed up his findings of evidence collected around the globe. Darwin realized that, though diverse, plant and animal species from the same continent had structures as well as character traits that were very similar. Species from different continents were however different (Buehler, 2009). Geographic diversity was also realized when species from islands were compared to those from the mainland. Darwin finches were the principal exhibit in devising the theory of evolution. According to Buehler (2009), Darwin stated that changes in different species over time occur in different direction if they are isolated and live away from each other over a long period of time. Times in evolution are very long and are measured in geological time for example, billions of years. The theory of plate tectonics, fossil records, and continental drifts support the principle of speciation as an outcome of long periods of geographic separation.

Comparative anatomy and comparative embryology also provide evidence for diversity and similarity. Analogous anatomical features that are used for the different purposes are often found in different living organisms. A good example is the human hand used for holding. The hand has got a skeletal anatomy identical to the fore limb of a cat used for walking. This skeletal anatomy is also similar to that of a whales flipper used for swimming as well as the wing of a bat used for flying. The skeletal structure of the four limbs of these animals suggests that they are all descendants of common ancestral animal. The process of evolution of modern animals, as stated by Buehler (2009), occurred independently of all other animals leading to development of a limb structure that fits the diverse usage. Modern animals have, however, not changed totally and as a result their structures are referred to as homologous structures. The principle of homology directs a structural likeness of body parts that are used to perform different activities. Based on the same fact organisms that are not related in any way have evolved similar body parts to carry out the same task. This likeness of structures for the sake of the same task is the outcome of convergent evolution. Structures such as these are referred to as analogous, indicating that their similarity is not an outcome of descent with modifications.

Contemporary molecular biology also provides some of the most convincing evidence of evolution. Modern molecular biology demonstrates that similarities at the molecular level can be used to verify evolutionary relationship. Molecular evidence supports the theory of evolution in a unique way. Based on the power of molecular analysis it can be concluded that the modifications Darwin referred to are the outcome of unsystematic alteration of genes. The instructions of making proteins in the body are stored in the genes. Physical traits, which are developed by proteins, are the ones that are modified through natural selection. This modification determines the ability of an organism to live in a particular environment and have as many offspring as possible. It is the number of fertile offspring, but not the survival for the fittest, that is used to measure Darwins fitness. Many organisms are very sensitive to climatic changes and if they do not adapt to climatic changes they become extinct.


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