Practice question

Optimal diet theory ranks prey by profitability, commonly energy obtained per unit handling time, E/h. A lower-ranked prey type should be accepted only when its profitability exceeds the expected rate of gain from rejecting it and searching for the preferred prey. The expression E2/h2 > E1/(h1 + S1) states precisely that condition: prey 2 yields energy fast enough to outperform the combined search and handling return associated with prey 1. As preferred prey becomes scarce, S1 rises and the right-hand rate falls, making prey 2 more acceptable. Energy alone or handling time alone cannot determine the decision because both enter the rate comparison. From an evolutionary perspective, traits persist when their net effects improve inclusive or direct fitness under prevailing conditions. The ecological terminology therefore summarizes both an immediate mechanism and its likely consequences across generations. A careful interpretation retains the assumptions of the underlying model and avoids extending it beyond available evidence. Within those assumptions, the keyed concept gives the most consistent account of the biological pattern and its expected outcome.