Evolution and Natural Selection

Genetic Diversity, Relative Fitness and Population Shift

Dec 6, 2007
Tami Port

Charles Darwin: Natural Selection & Evolution - public domain

We've all heard the phrase 'survival of the fittest' but how does it actually work? This article explores the basics of evolutionary theory and natural selection.

Although Charles Darwin had been recording his thoughts on natural selection since his voyage on the HMS Beagle, his ideas didn’t become widely known until 1858, when he and Alfred Wallace released a joint scientific paper introducing the concept of evolution by means of natural selection. This paper, along with Darwin’s subsequent publication, “The Origin of Species,” transformed the way science and society explained events in our natural world.

Others, such as John Lamarck, George Cuvier, James Hutton and Charles Lyell had thrown their hats in the ring asserting their thoughts on evolutionary theory, but Darwin was the first to describe the mechanism by which new forms and species could arise or evolve – natural selection.

Difference between Evolution and Natural Selection

Evolution

In biology, evolution can be defined as inheritable change in a population that ultimately results from the interaction of individuals with their environment. And its action over very large stretches of time explains the origin of new species, occasionally the elimination of existing species and ultimately the vast diversity of the biological world.

Today’s species are related to each other through common decent (ancestors that they share) and are products of evolution over billions of years.

Key concepts of evolution:

Any change must be inheritable (able to be passed on to the next generation).
These changes are regulated by natural selection.

Natural Selection

Natural selection is the mechanism of evolution, the process in nature by which only the organisms that are best adapted to their environment tend to survive and transmit their genetic characteristics to the next generation. Individuals less well adapted to their environment tend to be eliminated, where environment represents the combined biological and physical influences.

biological influences: include things like disease, competition, and predation
physical influences: include things like drought, fire, flood

Genetic Diversity, Relative Fitness and Population Shift

Three essential components of evolution via natural selection include:

Genetic Diversity: Populations of individuals are genetically diverse. Even members of the same species have characteristics that very from one individual to the next.
Relative Fitness: In any given environment, some individuals have characteristics that put them at an advantage over individuals who do not possess those characteristics.
Population Shift: In any given environment, those individuals who have advantageous characteristics will generally be healthier, live longer, and leave more offspring than individuals who do not possess those characteristics. The population will, over time, contain more and more individuals with the advantageous characteristic, and fewer individuals who do not possess the characteristic.

The Power Is in Natural Selection over Time: Reproductive Isolation & Extinction

Over time, natural selection can make sub-populations within a species genetically different enough so that they are no longer able to reproduce with each other, creating separate species (reproductive isolation). Two organisms are of the same species if they can produce fertile offspring with each other.

Natural selection does not always result in new forms or species. Natural selection may also result in the elimination of species from the environment (extinction).

The Selfish Gene: Whoever Passes on the Most Genes Wins!

The “goal” of all organisms is to live long enough to produce reproductive offspring. Individuals that can locate, harvest and utilize the resources from their environment the most efficiently, while minimizing the influence of limiting factors acting upon them, will be the most successful in continuing their genes to the next generation.

More Information on Evolution

For more information on evolution and general biology see the science website Science Prof Online or the Suite101 articles Pre-Darwinian Evolutionary Theory, Evolution as Theory & Fact and Natural and Artificial Selection.

Sources

Brown, Bryson (2007) Evolution: A Historical Perspective. Greenwood Press.

Campbell & Reece (2005) Biology, 7th Edition. Pearson.

Tami Port - Tami Port is a college professor of cell and microbiology and creator of ScienceProfOnline.com, a free science education website.

Comments

Jan 22, 2009 6:30 PM

Guest :

CrEaTiOnIsM

Apr 18, 2010 10:48 AM

Guest :

not very helpful! doesnt tell you about
:Fitness
:Adaptations
:Struggle for Existance
:Survival of fittest

Nov 1, 2010 9:32 PM

Guest :

It's a good basic introduction, explaining how microevolution can result from natural seleaction, although it does not explain corroboration of natural selection resulting in macroevolution.

Aug 11, 2011 1:43 PM

Guest :

Natural selection seems to be eliminating males in modern times although in humans, males do a very good job at this themselves as most murderers are male and males are their target most of the time. Than wars kill even more males. For example, the American Civil War killed 660 thousand males and 60 women. Even than, I would rather have seen a few thousand more males killed if it meant that NO women were killed.

One of the greatest con games in history is males making women think that we males are the superior sex. In reality, women and males are not even equal. Women are far superior to the males. Many things in your article shows this Although you may not agree that women are superior to male I believe that out of 100 good points, women have at least 90 of them We are tied in another 5 and males have the rest of the good points.

All of nature has a focus on the female and the male is just a supporting the female. This is true for humans too, women are the stars of this play called life and males are but supporting actors.

Antlers serve only to allow combat between males, and to get the males killed during hunting season.

Brightly colored or patterned plumage on male birds only puts them on display so the female just stands by to watch her counterpart be picked off by predators as she remains safe.

You mentioned male combat. Many species have males fighting often until one or both are dead and if both males are dead, the female just moves on to the next male.

I have seen birds whereby the male is chasing the female and she flies just in front of a moving car. The male does not notice and flies into the car. I cannot help but think that the female did this to get the male killed. No I do not think all animals are that smart but I do think females are. I have seen a female rabbit kill a male rabbit buy burning him in a hole he entered. Also I think if we check about 90% of the road kill would be, male.

Human males win almost all of the Darwin Awards, awards given to those who kill them self doing stupid things. It took several years and several hundred males before the first woman made the runners up list.

In humans it is the woman that chooses. Almost any woman can and does have sex with the male or males of her choice yet there are a great percentage of males that have never had nor ever will have sex with a woman. SHE calls the shots. Yes some males may force sex upon a woman (and in which case even though I am a male, to put it bluntly, that male should be hung by his balls in public after being stripped naked and having women tie the rope or better yet, thin wire around his nuts).

So in all of this agree or not, your article does again show that the female of every species is superior to the male and women (I will not call women a female as she is superior) are superior to the males. Because I am a male, do I regret that women are superior to us? Not in the least nor do I resent women are vastly superior to males. I am glad they are because when I look at most of the males around me, I would hate to think males are superior!
It is the male who gets down on his knee ( a sign that he knows she is superior to him) and ask her to marry him which she can refuse.

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