Welcome   |   Login   |   Sign Up   |

BIOSPHERE/ The Slime Mold Parable

Pierluigi Assogna comments on the evolution of the biosphere and how changes in individual species affect it, focusing on the example of the dictyostelium discoideum, or slime mold.

Dog Vomit Slime Mold Dog Vomit Slime Mold

The biosphere is the most complex environment that we know. Experts tell us that it evolved in roughly 3 billion years, starting from the first relatively simple components. This evolution is mainly due to one factor: finiteness of resources.

Complex systems find in their context the resources needed to maintain their configuration, and while those resources are available, there is no reason (excluding random events) to change the configuration. But when resources become scarce, and this is inevitable in a finite space and in the presence of the peculiar habit of organisms to reproduce and multiply, each species has two options: re-organize or perish.  Change is forced by the context.

Resource scarcity has another positive effect on evolution because of competition. Each single organism has to find the best ratio between resources used and effort spent in their search and utilization, resulting in an ever better living performance.

When scarcity becomes dramatic, another mechanism becomes vital: cooperation. This strategy enables different systems (organisms or aggregations of them) to devise new ways of using the same resources, or of using new ones, by coordinating their behaviors, that is by re-organizing.

Neither of these behaviors is substantially bad or good, both are fundamental for evolution, and have to be dynamically balanced according to the situations.

These drivers have shaped the ecosystem, promoting on the one hand the selection of the most efficient organisms occupying overlapping niches (that is competing for the same resources), and on the other hand, the organization of effective super-systems able to occupy new niches by combining the behaviors of different organisms.

Probably the most innovative example of cooperation is the endo-symbiosis of chloroplasts (in plants) and mitochondria (in animals). Both were originally competing prokaryotes (relatively simple unicellular micro-organisms), and at a certain evolutionary stage have been incorporated into the cells of advanced multi-cellular organisms, where they found a stable, competition-free and favorable environment, in exchange of which they provide vital services to their hosts.