Why do species live where they do? As discussed in Chapter 46, a population persists only in places where its members can tolerate the physical environment. Plants, for example, are sensitive to rainfall, freezing, and nutrient levels in the soil. The habitat occupied by a species usually contains other species, and the distribution of each species will also reflect interactions with the others, as the example of cacao illustrates. Competition between species can occur when different species use the same resources in the same place. Distinct species can coexist within shared habitat only if they use different resources, if they are active at different times, or if the local populations of one or both have so few individuals that resources are not limiting to their survival and reproduction. In other cases, like cacao, species persist only when other species that benefit their growth or reproduction are also present.