Evolution and Natural Selection
Genetic Diversity, Relative Fitness and Population Shift
Dec 6, 2007
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.
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