Example of how the current fitness component, b ( x
- x ), relates to final parental mass, x. Here, b(x0 - x) is a simple linear function of x. Shown are the fitness functions for parents that start off with high (heavy) and low (light) values of x0 – the resulting offspring fitness at any final mass (such as that at which future reproductive success fitness is maximised, x
) is greater for the parent that starts off with higher reserves, as it has allocated a larger amount of reserves to the offspring to reach this mass.