What defines an ecosystem's carrying capacity?

The carrying capacity of an ecosystem is fundamentally defined as the maximum population size of a species that the environment can sustainably support over time, given the available resources such as food, water, shelter, and space. This concept emphasizes the balance between resource availability and the needs of the organisms residing within that ecosystem.

The carrying capacity is crucial in ecology as it helps predict how populations can grow, stabilize, or decline based on the availability of resources. It takes into account not just the size of the population but also the interaction among different species, such as competition and predation, which can influence population dynamics.

In contrast, while the balance of predator and prey does impact population sizes and health, it does not directly define the carrying capacity itself. Maximum environmental stress refers to the limits an ecosystem can endure but is not a precise measure of carrying capacity, nor does total biomass directly equate to carrying capacity since different species have varying resource needs and tolerances. Therefore, option D accurately encapsulates the concept of carrying capacity in the context of sustainable population support.