Natural Selection Part One

Foundations and History Darwin was a British scientist who laid the foundations of the theory of evolution and transformed the way we think about the natural world. Darwin himself initially planned to follow a medical career, and studied at Edinburgh University but later switched to divinity at Cambridge. In 1831, he joined a five year scientific expedition on the survey ship HMS Beagle. On the voyage, Darwin read Lyell's 'Principles of Geology' which suggested that the fossils found in rocks were actually evidence of animals that had lived many thousands or millions of years ago. Lyell's argument was reinforced in Darwin's own mind by the rich variety of animal life and the geological features he saw during his voyage.

The breakthrough in his ideas came in the Galapagos Islands, 500 miles west of South America. Darwin noticed that each island supported its own form of finch which were closely related but differed in important ways. On his return to England in 1836, Darwin tried to solve the riddles of these observations and the puzzle of how species evolve. He proposed a Theory of Evolution occurring by the process of natural selection: The animals (or plants) best suited to their environment are more likely to survive and reproduce, passing on the characteristics which helped them survive to their offspring. Gradually, the species changes over time!

Darwin worked on his theory for 20 years Darwin worked on his theory for 20 years. After learning that another naturalist, Alfred Russel Wallace, had developed similar ideas, the two made a joint announcement of their discovery in 1858. In 1859 Darwin published 'On the Origin of Species by Means of Natural Selection'. The book was extremely controversial because the logical extension of Darwin's discovery was that homo sapiens was simply another form of “animal”. It made it seem possible that even people might just have evolved and destroyed the prevailing ideas on how the world was created. As in the cases of other such brilliant scientists (Newton, Galileo, Kepler Copernicus, etc..) Darwin was continuously attacked. However, (like his earlier counterparts) his ideas soon gained support and have since become the new system of understanding.

Evolution – The process that is responsible the progression of life forms on the planet. FACT FILE Evolution -All life on our planet shares a common ancestor -Life has a “history” – it has changed over time -Certain traits or modifications are inherited through reproduction, eventually branching species further apart -The first and only attempt to scientifically explain the diversity life The most important development in biology and related scientific fields The basis for many fields like genetics, medicine, psychology and agriculture just to name a few… Certain traits or modifications are inherited, branching species off from one another

The Mechanisms of Evolution How does it work? The major mechanism of evolution is Natural Selection, a process causing traits that are helpful for survival and reproduction to become more common in a population, and harmful traits to become more rare. 4 circles are born in ”Red Land” … 3 are blue and, for some reason, one is not… Example: A monster that loves to eat circles eats the circles that are the most noticeable… The remaining circle pairs up with the only other circle it can find – the remaining circle of another family. This circle survived because it was different too…not blue. Most of their children were blue, orange, purple, but one ended up a reddish color – a sort of mix of their two colors. Alas the monster returns it ate all but the one it could not find… Because Red Land was so huge and eons had passed, such circles thrived and reproduced with other such circles. The circles were still eaten by the monster (especially the “less” red circles) but not as many.

The “redness” of some of these circles was passed on from generation to generation so well that the way they eventually matched their environment seems almost “designed”. It is however only allowed because that trait increased chances of survival. This occurs because individuals with advantageous traits are more likely to reproduce, so that more individuals in the next generation inherit these traits. Over many generations, adaptations occur through a combination of successive, small, random changes in traits, and natural selection of those variants best-suited for their environment.