ABSTRACT
Cyclic phenomena, sometimes regular and sustained, sometimes complex, almost chaotic, are as ubiquitous in the biological world as they are in the physical. Cytoplasmic and cell surface oscillations such as those found in metabolic pathways, cellular respiration, and the propagation of action potentials, fall into a relatively narrow band in the high frequency end of the spectrum. The simplicity of circadian cycles is in sharp contrast to the complex cell population dynamics observed in many human disease states such as cyclic neutropenia, or in the immune response to antigenic challenge in experimental animals. The origins of complex, endogenous oscillations can be relatively simple. The most common example of an oscillatory biological system is a predator — prey feedback loop. The actual dynamical pattern depends upon whether a particular parameter entering the theory — a parameter involving cellular birth and death rates, exceeds certain thresholds.
