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