Final draft Essay 3

Influential factors for evolution: Environment, Mutations and Inheritance

Long before the science of genetics formally began with the great work of Mendel, many intellectuals wondered about patterns of similarities seen in nature. Scientists observed that there were certain resemblances among groups of organisms, but there was a common belief that all beings were made by God, and that He brought them to Earth the way they are today.  People believed that God’s creations were perfect, and that they would never change from the original form designed by the Creator.  The theory of evolution brought great controversy to this belief.  Evolution refers to the genetic changes in a population that can lead to the development of new species throughout time.  This major scientific theory explained to those, who were searching for answers, why there were groups of organisms that looked alike.  The theory of evolution provided a mechanism that demonstrated how the species changed.  Environment, mutations and inheritance are factors that drive natural selection and other evolutionary forces to cause evolution.

For each species there is a proper habitat.  The space, or niche in which species live, contains favorable conditions that allows them to survive.  All of the organisms living within such space are adapted to the conditions that are present there, i.e. temperature, light, nutrients (Pidwirny, M.).  For instance, the point of reproduction for a species of birds, the great tits, is affected by the change in temperature. If the temperature is too cold, it causes the birds to lay the eggs earlier, but if the conditions are too warm, it causes them to delay laying eggs (Visser et. al).  Changes that occur in conditions favorable for a certain species can greatly affect the way it develops.  Constant adaptation to these changes in the environment is critical for the survival of a species.  The great 19^th century naturalist, Charles Darwin, in his book The Origin of Species wrote: “As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form” (5).

Although Darwin did not know much about the mechanisms of inheritance, in his studies, he observed that certain characteristics were more frequent than others.  In order for new characteristics to appear, genetics changes, known as mutations, must occur first.  There are always some mutations arising, so the genetic material is constantly provided with variation.  Genetic changes are critical for the propagation of species: a species must be variable to adapt to the fluctuations in the environment.  The frequency of mutations that accumulate in a species is a key factor that determines the rate by which the species is adapting and therefore evolving (Stebbins and Ayala).  A species that contains the same genetic material for many generations will most likely become extinct, since its gene variants may no longer be favored by the new environmental conditions.  One of the leading evolutionary biologists of the 20^th century, G.L. Stebbins, along with Professor Francisco J. Ayala of the University of California point out the importance of mutations in an evolutionary aspect: “Genetic changes underlie the evolution of organisms; mutations are the ultimate source of the genetic variation that makes possible the evolutionary process” (967).

Mutations that occur in genes create new forms called alleles. These new forms are passed down through generations.  Most new alleles carry detrimental effects, but the inheritance of some new alleles can benefit survival of the species.  For example, research showed that 46,880 years ago dogs carried a mutation for black coat color and recently, scientists have found that wolves that live in forested areas inherited the allele from interbreeding with dogs (Anderson et al.).  Acquiring this melanistic allele benefited wolves who hunted in dark forests.  Dr. Anderson from Stanford University addresses the benefit of melanism in wolves:  “The potential selective value of dark versus light coat color has been suggested to include concealment during predation and/or indirect effects due to pleiotropy, but remains unresolved because the underlying gene(s) have not been identified”.  The inheritance of black coat allele has propagated quickly in wolf populations across North America.  Natural selection increased the frequency of the allele, but the value of this adaptation is still not well understood (Anderson et al.).

The environment provides the pressure on the genetic material (the DNA), and during cellular division, mistakes happen in DNA replication (mutations).  These mutations can be passed on to the next generation (inheritance).  While some of them are harmful, others can provide advantages and increase survival and reproduction of the species (selection).  Natural selection works on mutations that already exist in the population.  Evolution occurs when mutations are selected and passed on through generations.

Work Cited

Anderson, T. M., et al. "Molecular and Evolutionary History of Melanism in North American Gray Wolves." Science 323.5919 (2009): 1339-43.

Pidwirny, M. (2006). "Concept of Ecological Niche". Fundamentals of Physical Geography, 2nd Edition. Date Viewed. http://www.physicalgeography.net/fundamentals/9g.html

Stebbins, G. L., and F. J. Ayala. "Is a New Evolutionary Synthesis Necessary?" Science 213.4511 (1981): 967-71.

Visser, M. E., L. J.M. Holleman, and S. P. Caro. "Temperature Has a Causal Effect on Avian Timing of Reproduction." Proceedings of the Royal Society B: Biological Sciences 276.1665 (2009): 2323-331. Print