The Theory of Evolution
Charles Darwin and Natural Selection
CHARLES DARWIN proposed the theory of EVOLUTION BY NATURAL SELECTION after his ROUND-THE-WORLD EXPEDITION.
During this EXPEDITION, he made THREE observations:
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Individual organisms within a particular SPECIES show a wide range of VARIATION for a characteristic.
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Individuals with characteristics MOST SUITED to the environment are more likely to SURVIVE and BREED successfully.
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The characteristics that have enabled these individuals to survive are then PASSED ON to the next generation.
Using his observations from this EXPEDITION and years of knowledge of GEOLOGY and FOSSILS, he proposed the THEORY OF EVOLUTION by NATURAL SELECTION.
He detailed these ideas in his work, “On the Origin of Species” which was published in 1859.
Acceptance and Controversy
When Darwin’s theory was first proposed, it was CONTROVERSIAL because:
- The theory challenged the idea that GOD made all the animals and plants that live on Earth.
- There was INSUFFICIENT EVIDENCE at the time the theory was published to convince many scientists.
- Knowledge of genetics, including INHERITANCE and VARIATION was not known until 50 years AFTER the theory was published.
Lamarck's Theory
Jean-Baptiste Lamarck proposed a DIFFERENT theory which said that CHANGES of characteristics in an organism occurred DURING ITS LIFETIME rather than gradually through several generations.
He said that if a characteristic was used A LOT by an organism, then it would become MORE DEVELOPED during its lifetime, and these developed characteristics were PASSED ON to the organism's OFFSPRING.
For example: If an animal used its leg muscles a lot to escape predators, its legs will develop to get stronger and longer. The offspring of this animal would then also inherit these stronger and longer legs.
We now know that this is NOT true and in the vast majority of cases this type of inheritance CANNOT occur.
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