In the small scale, deterministic factors are usually dominant, though some types of unpredictable behavior are present, for instance when deterministic chaos is involved. In the large scale, however, continuous, random changes in the trophic links move the system towards a critical state characterized by a high unpredictability and sensitivity to small perturbations. Here is worth emphasizing that spatial degrees of freedom can play a very important role. This situation allows a given ecosystem to explore a wide range of interactions and, in the long run, eventually triggered by external causes, extinction can occur. Because of the intrincate network of couplings obtained at the critical state, the problem of which species will be gone is essentially unpredictable.
Power laws are the statistical counterpart of punctuated equilibrium.
The global pattern is emergent, resulting from the generation of complex correlations among species. To sum up, we have shown that our model of large-scale evolution is able to recover the observed evolutionary patterns. The main consequence of our study is that the network complexity of a given ecosystem always grows in time leading to essentially random nets of connections. In this sense, the Red Queen picture, where changes are made in order to adapt the system to the biotic environment, should be replaced by an always changing system were species are gone as a consequence of the unpredictable web of biotic relations. The observed fractal properties of the fossil record would be a direct result of this unpredictability in the critical state.