Evolution

From Biology

Evolution is the theory of Lamarck completed by Charles Darwin and Wallace.

[edit] Theory of acquired characters (by Jean-Baptiste Lamarck)

Lamarck was prior to all this theory. His theory states that acquired characteristics transmit to the offspring. Thus, a giraffe that stretches its neck changes it and transmit longer necks to its offspring. It is a false theory, as has been found in genetics research. Nevertheless, in genetics there is a mild version of this found in retroviruses.

[edit] Main theory (by Darwin and Wallace)

It states that there are a lot of variations in living organisms (mutations) and these variations lead to changes in the offspring. These changes can be beneficial to the new organisms or can sometimes be lethal. The natural selection operates here because the organisms that cannot survive to have offspring make their characteristics disappear forever. So, it is the aptest (not the strongest) the one who survives. As the food resources are limited, there is a struggle for life as there is always more organisms that those who can live. These can be appreciated in rapid-replicating organisms like bacteria. Left alone, they would duplicate every 10 minutes. Theoretically, there would be 16'777.216 of them in 4 hours. In 10 hours they would be aproximately 590 millions. In real life, they are limited by resources and space and never get to be that big number.

Another key aspect to evolution is the formation of new species. As organisms vary over time, they tend to differ very much from the original species. If they are isolated, they can form a new variety which cannot interbreed with the original species, thus forming a new one. A species is the smallest unit of classification in which individuals can interbreed and can have viable offspring. That is the case of the mule, for instance. As horse and donkey come from different species, they interbreed but cannot have viable offspring (the mule is sterile).

These theory was submitted to the scientific community in a common work signed by Darwin and Wallace. Wallace had sent his work to Darwin while he was thinking about the theory. Darwin and his friends decided Wallace also deserved credit for the theory, because he was as discoverer as Darwin.

[edit] Origin of Species

See Origin of Species full article

Darwin published a joint writing along with Wallace about this subject. After some time, Darwin completed the theory in a long book called the Origin of Species.

In a pseudo-equation: Interbreed + Viable offspring -> Species