Stepping back from a complexity argument for a moment, the article makes mention of bacterial chemotaxis.
Eukaryotic chemotaxis is particularly interesting;
“Due to their small size and other biophysical constraints, E. coli cannot directly detect a concentration gradient. Instead, they employ temporal gradient sensing, where they move over larger distances several times their own width and measure the rate at which perceived chemical concentration changes.”
https://en.wikipedia.org/wiki/Chemotaxis
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Several mathematical models of bacterial behaviors: (shown in Wiki):
Migration (e.g., basic differences of bacterial swimming, movement of unicellular eukaryotes with cilia/flagellum and amoeboid migration)
Physico-chemical characteristics of the chemicals (e.g., diffusion) working as ligands
Biological characteristics of the ligands (attractant, neutral, and repellent molecules)
Assay systems applied to evaluate chemotaxis (see incubation times, development, and stability of concentration gradients)
Other environmental effects possessing direct or indirect influence on the migration (lighting, temperature, magnetic fields, etc.)
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