Final answer:
The most useful measure of tolerance is standard deviation, as it quantifies the variation of conditions a species can withstand. Habitat is critical to a species' survival, with some being generalists and others specialists. Ecosystem ecology plays a role in identifying new species and understanding pollutant effects.
Step-by-step explanation:
The most useful measure of tolerance in the context of Biology is standard deviation. Standard deviation is a statistical measure that quantifies the variation or dispersion of a set of values. In the study of ecology, standard deviation can indicate the range of conditions (such as temperature, pH, salinity) under which a species can survive, hence showing the tolerance of a species to environmental changes.
Habitat is another crucial aspect, which refers to the natural environment in which a species lives. In ecological studies, the habitat includes both biotic and abiotic factors and is critical to a species' survival and reproduction. Generalists, like the small white butterfly (Pieris rapae), can thrive in various habitats, whereas specialists, such as the large blue butterfly (Phengaris arion), may have very specific habitat requirements. Lastly, the rapid identification of new species and understanding the effects of pollutants are significant functions in ecosystem ecology, aiming to understand how ecosystems function and support biodiversity.