 a self-organizing biological event that maintains the organism’s complex internal structure. The materials that organisms are made up of are intrinsically unstable and must therefore be constantly repaired and renewed, or else the organism dies and its remains decay. An organism must constantly take in new particles, reconfigure and assimilate them into its living fabric, and expel those that are no longer useful to it. An organism’s life enables it to persist and retain its characteristic structure despite constant material turnover. (Olson 2007: 28)