Natural Selection

Chapter Summary

1. Much of the research on evolution by natural selection done since Darwin relies on a solid and ever-expanding understanding of the process of genetic transmission.
2. Evolution by natural selection is the inevitable consequence of three simple conditions: variation, inheritance, and differential reproductive success.
3. Natural selection does not act directly on genotypes: It operates on phenotypic differences among the individuals in a population.
4. Evolution by natural selection is a process by which the characteristics of a population—not those of an individual—change over time.
5. The relative fitness of a trait or gene is defined as the expected reproductive success of an individual with that trait or gene, relative to other members of the population.
6. An adaptation is an inherited trait that makes an organism more fit in its abiotic and biotic environment, and which has arisen due to the direct action of natural selection for its primary function. An exaptation is a trait that serves one purpose today, but served a different function in the past.
7. Evolutionary processes can be observed, and manipulated, in real time in the field and in the laboratory.
8. The process of natural selection operates on physical structures in the material world, and as such is constrained by the same physical and mechanical laws that limit the realm of possibility for human engineers.
9. The process of natural selection has no way of anticipating the future, nor can it plan ahead by multiple steps. Selection favors changes that are immediately beneficial, not changes that may be useful some time in the future.