Biologists have long been worried about the possible effect of the extinction of species on whole ecosystems. A. Conservation biology studies indicate that the loss of a single important species may bring temporary change to an ecosystem but it seldom results in lasting damage. B. Ecosystems having species with similar functions but different responses to adverse conditions can survive environment disturbances. C. The Minnesota grassland study by Tilman and Downing presented evidence that the greater the diversity of species in an ecosystem, the more stable the ecosystem. D. The absence of sea otter predation in a Pacific kelp bed ecosystem dramatically changed the entire ecosystem by stabilizing the total kelp population. E. The findings of the Minnesota grassland study by Tilman and Downing indicated an equal number of drought-resistant and drought-tolerant plant species in species-rich plots. F. More research is needed on the relationship between species diversity and ecosystem stability, though a simple explanation is unlikely.