Darwin noted four things from his observations:
1. All organisms produce an abundance of offspring, many more than is necessary
2. There is a fairly constant population size over time for any particular organism
3. Within a species there is a wide range of features, due to different alleles
4. Some variations are passed on and inherited by the offspring
From these Darwin decided that all organisms struggle for survival and so have to produce many offspring to ensure that some do survive.
He also concluded that for a species to survive, the best (or ‘fittest’) of them must survive long enough to reproduce and pass on their genes.
It has three essential parts:
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It is possible for the of an organism to occasionally change, or mutate. A mutation changes the DNA of an organism in a way that affects its offspring, either immediately or several generations down the line.
- The change brought about by a mutation is either beneficial, harmful or neutral. If the change is harmful, and then it is unlikely that the offspring will survive to reproduce, so the mutation dies out and goes nowhere. If the change is beneficial, then it is likely that the offspring will do better than other offspring and so will reproduce more. Through reproduction, the beneficial mutation spreads. The process of culling bad mutations and spreading good mutations is called natural selection.
- As mutations occur and spread over long periods of time, they cause new species to form. Over the course of many millions of years, the processes of mutation and natural selection have created every species of life that we see in the world today, from the simplest bacteria to humans and everything in between
During the 19th century, the Austrian monk laid the foundations of , although his work, published in 1866, was not recognized until after the century had closed. But the British scientist towers above all other scientists of the 19th century. His publication of On the Origin of Species in 1859 marked a major turning point for both biology and human thought. His theory of by natural selection (independently and simultaneously developed by British naturalist ) initiated a violent controversy that still has not subsided. Particularly controversial was Darwin’s theory that humans resulted from a long process of biological evolution from apelike ancestors. The greatest opposition to Darwin’s ideas came from those who believed that the Bible was an exact and literal statement of the origin of the world and of humans. Although the general public initially castigated Darwin’s ideas, by the late 1800s most biologists had accepted that evolution occurred, although not all agreed on the mechanism, known as , that Darwin proposed.
