The theory of evolution describes how more complex organisms arrive from less complex organisms. This theory can be explained using natural selection.


Individuals within a species have natural genetic variation due to mutations. The individuals that have mutations that make them more adapted to their environment survive and breed, passing on their genes to the next generation.


Through genetic analysis, as well as looking at an organism’s characteristics, scientists are able to group organisms to find out how closely related they are to each other. Species that have a more recent common ancestor, are said to be more closely related.


The theory of evolution by natural selection was developed over time by many scientists. The scientist Lamarck thought that characteristics would become more developed if they were used to more often. However, the modern theory of evolution was developed by Charles Darwin in his book On The Origin Of Species.


The reasons why many disagreed with Darwin’s theory at the time was:


  • It went against common religious beliefs.
  • There wasn’t enough evidence to conclusively prove his theory.
  • Darwin could not explain how these useful characteristics spread to the next generation. It wasn’t until the scientist Mendel discovered genetics 50 years later that this could be explained.


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