Equation 3 · Part 9 · Comparing the Main Approaches to Evolutionary Biology and Ecology
Denominator: 1 + s p_t
What this part means
The complete quantity below the fraction bar; it must be nonzero for this division.
Its job in the formula
1 + s occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.
Full expression→Denominator: 1 + s p_t→Article meaning
The passage around this formula
A basic model of directional selection acting on a single locus, of the kind both the field and laboratory results above are ultimately interpreted against, describes how an allele’s frequency changes by one generation under a constant selection coefficient s favoring the allele at frequency p : . The equation exposes the model’s real content: selection is strongest while the favored allele is at intermediate frequency, where is largest, and weakens automatically as the allele nears fixation or loss, purely from the algebra of the denominator — a pattern of decelerating change that shows up empirically in both the Grants’ beak-size tracking and the LTEE’s…
Learn the underlying idea
A fraction a/b means a divided by b. The top number is the numerator; the bottom number is the denominator, and it cannot be zero.
Open the illustrated fractions: division written vertically guide →
Sources cited in the article section
- [3] E. coli long-term evolution experiment ↗
- [4] Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli ↗
These citations provide research context; check each source for the exact claim it supports.