- Evolution by natural selection takes place when some individuals survive and reproduce better than others in a particular environment and the heritable characteristics of a population change from one generation to the other due to that.
- Fitness is measured by the number of descendants left by individuals in a population.
- Evolution is not perfect: Evolved individuals might have characteristics that are suited to the environments of their ancestors but not so much to their current environments.
- Fitness is relative: evolved individuals can be the best fit for their current environments but not the perfect fit.
- Precise matches between an organism and its environment may equally be seen as constraints making such organism dependent on such specific environment.
- Does fitness depend on the number of offspring only and why?
- What is the ultimate fitness?