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Equation 3 · Part 1 · Comparing the Main Approaches to Evolutionary Biology and Ecology

Symbol p_t+1

pt+1=pt(1+s)1+s ptp_{t+1} = \frac{p_t (1 + s)}{1 + s\, p_t}
pt+1p_{t+1}

What this part means

ptp_t+1 is the next indexed value computed from the current indexed quantity and the update terms shown on the right.

Its job in the formula

ptp_t+1 is the next indexed value computed from the current indexed quantity and the update terms shown on the right.

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 : pt+1=pt(1+s)1+s ptp_{t+1} = \frac{p_t (1 + s)}{1 + s\, p_t}. The equation exposes the model’s real content: selection is strongest while the favored allele is at intermediate frequency, where pt(1−pt)p_t(1-p_t) 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…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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Sources cited in the article section

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