Cyclic processes in biology are ubiquitous: they can be found in nearly every organism on earth. The time-scales of these processes vary from microseconds, in the case of Ca2+ oscillations, over hours, in the case of the circadian rhythm, to years in the case of insect eclosion rhythms. Furthermore, the spatial scale is huge: it ranges from cyclic molecular processes within one cell, for example in single cell circadian clocks, over complex oscillator networks of thousands of neurons in the mammalian circadian pacemaker, to population wide predator-prey oscillations. This thesis picks out three examples from this enormous spectrum of biological oscillations and analyzes properties and advantages of these rhythms in a theoretical manner.