Recently after watching a BBC Earth documentary, I had a dream that I was standing in a vast African prairie, being soaked up in the sunset glow, breathing the hot but fresh air with faint dung smell, being watched by a group of giraffes that are eating leaves on the sparse trees, afraid of being attacked by hungry lions, and feeling the insects and microbes in the grass by my naked feet. I felt joy, fear, insignificance and real, as part of this vastness.
Distinct ecosystems are found at all levels of biological organization. Prey, predators and decomposers interact within a habitat; microbes cross-feed and compete for resources within artificial culture or natural community; different types of cells interact by exchanging metabolites within the body, etc. We may ask, are there any basic properties of ecosystems? Could we create an artificial ecosystem in which these phenomena emerge spontaneously?
The artificial ecosystem: 'Number Soup'
Our artificial ecosystem is a 'number soup', where we represent resources/metabolites by integers, and organisms by addition operations on those integers. The underlying mechanism is extremely simple.
Here is an example of evolution in the 2-metabolite system, where S11, S12 and S22 represent the populations of different species,
Below is a movie of the interactions of different species for the same time period.
In the number soup, we observed a rich variety of phenomena that are related to natural ecosystems:
1) The system always self-organizes to consume up all the available resources. We think this should be a general trend for all natural ecosystems.
2) The origin of what is known as "cross-feeding". Imagine you encounter two species in the wild that require each other to survive. A question that may come to you, and is often asked by researchers, is which of the species came first. The observation of number soup gives you the insight that reciprocal cross-feeding evolves in a number of stages.
4) The very simple interactions in the system produce rich biodiversity. It provides insight into the question of why in a certain natural ecosystem, the number of coexisting species is neither much more nor much less than what has been observed.