What is 'survival of the fittest?'

1. What is ‘survival of the fittest’?

- ‘Survival of the fittest’ is a phrase way to describe the principle behind the theory of evolution by natural selection, originally proposed by Charles Darwin in 1859

- According to the theory, life on Earth began from much more simple forms of organisms

- Organisms we see today are more complex because they have continually changed and diversified over millions of years through a process of evolution

- Evolution depends on natural selection. Survival of the fittest describes the process of natural selection because natural processes select the fittest organisms to survive and evolve
 

2. What is fitness and what is a fit organism?

- Fitness describes an organism's ability to survive in its environment (e.g. ability to find food and shelter, avoid getting eaten)

- To survive in its environment, an organism’s traits have to be well adapted to it

- Between members of any given species, there are differences in their traits (e.g. body size or camouflage), which means that some members will inevitably be better at surviving than others
 

3. How does this process lead to evolution?

- Differences in traits are due to differences in genes, which are passed down from parents to offspring in each generation

- Fitter organisms have a better chance of surviving, which also means a higher chance of successfully reproducing

- Therefore, fitter organisms will contribute more offspring to the next generation, whereas the individuals that are badly adapted to their environment will be less likely to survive and reproduce, and will contribute less offspring

- Since traits are inherited through genes, the next generation will be overall fitter than the last (i.e. through natural selection of traits that allow effective adaptation)

- If this process is repeated over many generations, species will gradually evolve