Chapter 3 of 10All chapters
Chapter 3 of 10
Selection
Filtering, not striving.
Fitness
Fitness means reproductive success in a specific environment, not strength or health. Being smaller, duller or more cooperative raises fitness whenever it leads to more surviving offspring.
- Survival of the fittest is a poor phrase, since survival is only a means to reproduction.
- A trait that helps in one place can be fatal in another.
Kinds of selection
Directional selection pushes a trait one way, stabilising selection favours the middle, and disruptive selection favours both extremes. Sexual selection can push traits that survival alone would not.