evolution

The purpose of this post is to introduce the readers to the concepts of evolution. Its purpose is to discuss this most important issue in simple terms and give information about the theory of evolution and its processes. Overall, concepts regarding the following image will be discussed.

Picture 1. Cliché “evolution” image (1)

The theory of evolution was first introduced by Charles Darwin in his book called “The Origin of Species” in 1859. The main idea discussed in the book is that populations evolve over the course of generations through a process of natural selection, which is the gradual, non-random process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers. (Natural selection will be further discussed later on.)

The idea of evolution was not a new concept. On the contrary, the concept of evolution can be traced as back as the philosopher Aristotle (4th century BC) and even the philosopher Empedocles (5th century BC). However, Darwin’s work is crucial because of the fact that not only did he discuss the concept of evolution in depth, but he also provided scientific evidence to support his theory.

The ideas of Charles Darwin challenged the idea that man was created by God and, as it was expected, were initially rejected from the scientific public of mid 19th century England. However, despite its initial rejection, Charles Darwin made concepts such as the evolution of species known to the wider public and sparked discussions in scientific circles.

Anyway, enough with the history of the theory of evolution. For more information about the life and work of Charles Darwin, you can watch the following video (3 parts), which narrates the biography of Charles Darwin in a humoristic manner.

Part 1

For parts 2 and 3 click on the links below:

Part 2 (8:35)

Part 3 (7:17)

So, what is evolution?

Evolution can be defined as the gradual development of something. Given that this “something” is a living organism, we refer to the process of its evolution as biological evolution, which is the change in the inherited characteristics of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules, such as DNA. 

This simply means that there is a difference between the genetic information an individual receives from his ancestors and the genetic information this individual gives to its descendants (heredity). Naturally, this difference (mutation) is very small and its consequences can’t be seen. However, considering that this process is repeated for some million years, adding up these small differences may result to something completely different from the initial individual.

The main reason that this process occurs and that determines these small genetic differences that are passed on to our descendants is adaptation. Simply, we need to adapt to our environment and in order to do so we change bit by bit (variation). Naturally, the more drastic these changes are and the greater our need for adaptation are, these differences become bigger and changing more evident.

The most important means of evolution is natural selection. It is t he process by which genetic mutations that enhance reproduction become and remain, more common in successive generations of a population. Natural selection is often described as “survival of the fittest”, however “fittest” in the specific context refers to the best adapted to the environment species.

The concepts of natural selection, variation and mutation are explained in the following diagram.

Picture 2. Evolution through natural selection(2)

For a more detailed explanation of the concepts mentioned above, you can watch the following video:

Similar to the natural selection is the process of artificial selection. However, instead of nature taking care of the process of adaptation, humans intervene and actually create new breeds, or even species, that have desired traits of other species. Well, one might think of a mad scientist experimenting and creating monsters, however these “monsters” are really familiar to us, yet not everyone knows that they are a result of artificial selection. Some examples of such “monsters” are:

Picture 3. A Great Dane, a Pug and a Chihuahua (3)

Well, surprisingly enough, Chihuauhas, Pugs and Great Danes, as well as numerous other dog breeds, are a result of artificial selection.

So, concluding on evolution, species tend to adapt to their environment. This process, however, can take millions of years and if we don’t actually intervene, meaning the artificial selection process, we do not interfere in this process.

Well, not really. But actually, does the human impact on the environment affect the evolution of species?

Well, the answer is quite simple. Not only does our impact on the environment affect the evolution of species, but also we have accelerated this process, making its consequences immediate and easily identifiable. It would be easy to discuss the evolution of a microorganism as a result of environmental changes, however it would be as easy to forget it. So instead, the case of the Grolar Bear will be discussed.

Picture 4. A Grolar or Pizzly bear(4)

As the name suggests, the Grolar or Pizzly bear is a hybrid between a Polar and a Grizzly bear. They have a gray color and their size is between this of a Polar and a Grizzly bear. Generally, their characteristics are a mixture of the characteristics of both species, which differ significantly.

It was first observed in 2006 in the far north territories of Canada. At first scientists paid no attention. However, after some more appeared, they checked their DNA and they reached the conclusion that the Grolar bear is a mixture of the two species.

The reason that led to interbreeding is the environmental change, the result of which are evident in the Arctic. As the Arctic ice cap disappears, the two species have come to contact. The decreasing population of Polar bears has led the populations move to the southern territories of the Arctit. At the same time, the rising temperature has led Brown bears towards the northern territories of their habitat and thus the two species have come to contact.

Although this may seem harmless, or even good for the well-being of the species, it is actually quite dangerous and may even lead to the extinction of one of the species (most possibly the Polar Bear, as it is fewer in numbers). In similar cases in the past, one specie became subsumed to the other, with the rarer specie becoming extinct eventually. Moreover, scientists claim that as a consequence of this crossbreeding polar bears will adapt to higher temperatures, thus not being able to survive in their natural habitat.

The fact that this whole procedure has taken place during the past couple of decades can be at least concerning. The fact that we have accelerated a process that would ,under normal circumstances, last for hundreds of years so much that it took place in just 20 is at least frightening. Finally, the fact that except for the Grolar bear another 34 potential hybridizations have been listed, can only make us think of the consequences of our lifestyle and fortunately change it.

Citation:

  1. Hall, B. K.; Hallgrímsson, B., eds. (2008). Strickberger’s Evolution (4th ed.). Jones & Bartlett. pp. 762.
  2. “11 Amazing Hybrid Animals.” Mother Nature Network. N.p., n.d. Web. 15 Nov. 2012. <http://www.mnn.com/earth-matters/animals/photos/11-amazing-hybrid-animals/mixing-things-up&gt;.
  3. “Biology Reference.” Natural Selection. N.p., n.d. Web. 15 Nov. 2012. <http://www.biologyreference.com/Mo-Nu/Natural-Selection.html&gt;.
  4. “Science Online Seminar: Examining Natural Selection in Humans.” Science Online Seminar: Examining Natural Selection in Humans. N.p., n.d. Web. 15 Nov. 2012. <http://science.cnpg.com/lsca/webinar/sabetischaffner/20060626/&gt;.
  5. “Natural Selection Has Strongly Influenced Recent Human Evolution, Study Finds.”ScienceDaily. ScienceDaily, 23 Oct. 2005. Web. 15 Nov. 2012. <http://www.sciencedaily.com/releases/2005/10/051023115936.htm&gt;.
  6. “Introduction to Human Evolution.” Human Evolution by The Smithsonian Institution’s Human Origins Program. N.p., n.d. Web. 15 Nov. 2012. <http://humanorigins.si.edu/resources/intro-human-evolution&gt;.

Pictures

  1. The New Diplomacy. N.d. Photograph. : The Evolution of Diplomacy. Web. 12 Nov. 2012. <http://thenewdiplomacyg.blogspot.gr/2010/10/evolution-of-diplomacy-write-about-what.html&gt;.
  2. Mutation and Selection Diagram.N.d. Photograph. Wikipedia. Wikimedia Foundation. Web. 12 Nov. 2012. <http://en.wikipedia.org/wiki/File:Mutation_and_selection_diagram.svg&gt;.
  3. – Get It Right 3rd Time around. N.d. Photograph. Get It Right 3rd Time around. Web. 12 Nov. 2012. <http://joicemaduaka.blogspot.com/&gt;.
    Dog Breed Info Center®, DBI. N.d. Photograph. Dog Breed Info Center®, DBI. Web. 12 Nov. 2012.                                                  <http://www.dogbreedinfo.com/index.htm&gt;.- Pictures of Cute Puppies and Dogs. N.d. Photograph. Pictures of Cute Puppies and Dogs. Web. 12 Nov. 2012. <http://www.pictures-of-puppies-and-dogs.com/&gt;.
  4. Grolar Bears and Narlugas: Rise of the Arctic Hybrids | OnEarth Magazine. N.d. Photograph. Grolar Bears and Narlugas: Rise of the Arctic Hybrids | OnEarth Magazine. Web. 12 Nov. 2012. <http://www.onearth.org/article/grolar-bears-and-narlugas-rise-of-the-arctic-hybrids&gt;.
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