Wednesday, March 11, 2015


Introduction to the Theory of Evolution
by
Adyatma Irawan Santosa
(Doctoral Candidate of Ankara University, Turkey)

 1.    Introduction
            Life, as we know it, is never statics but instead is always changing. The next generation in a population is always differs slightly (both appearances and genetics) from the previous ones. Those differences, over a very long periode of time, actually accumulate into changes of the said population. The phenomena of slowly change of all form of life over generations is what we call as Evolution.
            Offspring differs from their parent in minor ways due to addition of new genes via mutation and/or mixing of available genes via sexual reproduction. If the resulting changes are beneficials, the individual is more likely to survive and reproduce. By this means, organisms will have better adaptation to their living environments. Isolated populations, which reproduces among themself, experience greater effects of this changes and eventually can emerge into new species (speciation).
The idea of some species changed into other species is not something new in human history. Philosophers from ancient Greek, Roman, and Chinese had proposed that plants, animals, even human, was descendant of other tpe of organisms. However, modern definition of evolution only recently began with Charles Darwin's works and the subsequent publication of his book On the Origin of Species in 1859. Furthermore, Gregor Mendel's experiments also contributed to explain the hereditable traits via genetics. Nowadays, Evolution is one of the principal scientific theories that biologists use to study life and is applied in many disciplines.

2.    Evolution Mechanisms
Natural selection
Traits that provide better chance in survival and reproduction become more and more common in a population after successive generations because individu that posses advantages over their competitors is more likely to pass their traits to the next generation than those who does not posses such advantages.
Biased mutation
            Mutations that occurs more frequent among two different mutations is the one that more likely fixed in a population and leading to an evolution. The other mutation was usually eliminated because either there is no benefit to keep it or it is too costly to be kept.
            Genetic drift
            Allele frequency differs from one generation to other because allele are subject to sampling error. By chance, this mechanism able to remove some alleles from a population and thus leading to evolution.
            Genetic hitchhiking
            A set of alleles usually grouped together into a haplotype and they are also inherited together. If an allele is particulary beneficial, it can also make other alleles in their haplotype to become more common in a population through natural selection.
            Gene flow
            With the absence of gene flow between them, two isolated populations of the same species will eventually developed into two different species.

3.    Samples of Evolution
Peppered moth
The dark-colored variety of this moth (Biston betularia f. carbonaria) was only found in a very small number compared to the white-colored variety (Biston betularia f. typica). But, they become more common and eventually surpassed the number of white-colored variety during industrial revolution in England. This happened due to dark color was an effective camouflage which provides defense mechanism against their bird predators in industrial revolution polluted enviroments. Birds more easily caught white-colored variety and thus significantly reduced their number. This phenomena is considered as the most direct and the most simple example of theory of evolution.

            Antibiotics resistance in bacteria
            The use of antibiotics in human and veterinary medicine increases selective pressure in bacteria populations. Antibiotic applications kill off all susceptible bacteria and leave resistant bacteria to survive and thrive. In this case, it can be said that the particular species of bacteria evolved: individual with better advantages (resistance to antibiotics) passes their traits to the next generation and eventually become more common individuals in a bacteria population.

4.    Application of Theory of Evolution in Agriculture
Selective breeding of plants and animals
            Individual plants and animals with more beneficial traits (in human views) are selected to breed for generations in thousand years by human. As results, important species like rice, wheat, maize, cow, horse, and dogs have significantly different appearances and traits than their ancestors. Modern maize for example, after millenias of selective breedings, has very large kernels compared to its wild ancestor, toesinte. Extremely muscular Belgian Blue cows which actually suffer from defective heritable condition called “double-muscling” is another example. They were selected to pass the defective condition to their offsprings since it make their meat low in fat, thus increase their economic value.
Plant resistance to diseases
            Individual plants with higher resistance to diseases caused by bacteria, fungi, and or virus were selected and breed so that their offsprings inherit the traits and even have higher resistance to diseases. These processes enable individual with higher resistance to diseases to become more common in a plant population, thus can be said that the particular plant species evolved.

5.    Theory of Evolution Weakness
Theory of evolution is so complex because it observes processes that happened since the beginning of life on earth, hundred millions years ago. No wonder, since the birth of this theory by Charles Darwin, it has raised controversies and its validity has been heavily debated. Many ‘weaknesses’ of this theory has been proposed by the critics, which mainly relied on the lacks of available evidences and data at that time. With more evidences gained and better understanding in ecology, genetics, medicine, etc., eventually some of these ‘weaknesses’ have been rebutted by scientific community. Assumption that theory of evolution violates the 1st and 2nd Law of thermodynamics, as well as Law of biogenesis have been proven as false. The idea that theory of evolution is not observable was also proven to be false with the discovery of Transisional fossils. As result of these foundings, theory of evolution currently has gained widely acceptance among scientific community.
However, theory of evolution and scientists that support it still have not found the answer of some questions. How life developed from non-life has yet to be understood. Other problem includes the fact that currently available evidences so far only indicated small changes in organisms structure, but observable fully functional significant changes has yet to be found. Futhermore, the odds that random changes (as suggested in theory of evolution mechanisms) would produce million complex organisms in perfect shape is very small.

6.    Closing
With the overwhelming evidences, wide acceptance by scientific community, and vast applications of this theory we can conclude that this theory is valid and useful to understand some aspects of life. However, to which extent the validity of this theory is still a subject for discussions. Wheather we need to add other factors (such as God) as the real ‘inteligent designer’ behind this theory mechanisms is also a matter for further discussion.

References
Agrios, G. N. 2005. Plant Pathology. Academic Press: New York.
Antibiotic Resistance. sciencedaily.com. Retrieved 12 March 2015.
Essential List of Scientific Weaknesses of Evolution Theories. strengthsandweaknesses.org. Retrieved 12 March 2015.
Introduction to Evolution. Wikipedia.com. Retrieved 12 March 2015.
Understanding Evolution: Gene Flow; Sex and Genetic Shuffling. evolution.berkeley.edu. University of California, Berkeley. Retrieved 12 March 2015.

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