Th Origin species was published in year 1859 by Charles Darwin ,It introduced the theory that populations evolve over the course of generations through a process of natural selection,Darwin's book was the culmination of evidence he had accumulated on the voyage of the Beagle in the 1830s and expanded through continuing investigations and experiments after his return.
Darwin's theory is based on key observations and inferences drawn from them:
- Species have great fertility. They have more offspring than can grow to adulthood.
- Populations remain roughly the same size, with small changes.
- Food resources are limited, but are relatively stable over time.
- An implicit struggle for survival ensues.
- In sexually reproducing species, generally no two individuals are identical.
- Some of these variations directly impact the ability of an individual to survive in a given environment.
- Much of this variation is inheritable.
- Individuals less suited to the environment are less likely to survive and less likely to reproduce, while individuals more suited to the environment are more likely to survive and more likely to reproduce.
- The individuals that survive are most likely to leave their inheritable traits to future generations.
- This slowly effected process results in populations that adapt to the environment over time, and ultimately, after interminable generations, these variations accumulate to form new varieties, and ultimately, new species.
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