If humans did not need organisms to consume the dead skin on our skin, the organisms who perform this task would not exist. Diversity would be less if mutualistic relationships between organisms did not exist. To explain the process in a simplistic manner, if one organism in the second trophic level is to be supported, then 10 organisms are needed in the first trophic level. The island ecosystem is more susceptivel to large changes in its ecosystem if a non-native species is introduced because an island ecosystem is simplier than an ecosystem found on a continent. Those ecosystems with less diversity are less able to maintain a dynamic balance.
Biodiversity is decreased when non-native species are introduced for several reasons.
Some organism are eliminated by direct competition. Therefore, the exotic species not only replaces one species with itself but it also eliminates many other species because the role of the species that it eliminated has been abolish. Think about the parasites and mutualistic relationships that exits between species. When a species is eliminated all these relationships cease. Circle the ONE question you are answering.