Universality in bio-rhythms: A perspective from nonlinear dynamics.

Bio-rhythms are ubiquitous in all living organisms. A prototypical bio-rhythm originates from the chemical oscillation of intermediates or metabolites around the steady state of a thermodynamically open bio-chemical reaction network with autocatalysis and feedback and is often described by minimal kinetics with two state variables. It has been shown that notwithstanding the diverse nature of the underlying bio-chemical and biophysical processes, the associated kinetic equations can be mapped into the universal form of the Lie´nard equation which admits of mono-rhythmic and bi-rhythmic solutions. Several examples of bio-kinetic schemes are examined to illustrate this universality.