2014 Reprint of Original 1962 American Edition. Exact facsimile of the original edition, not reproduced with Optical Recognition Software. This important introduction to theoretical biology is a classic work in its field. Already in the 1930's Bertalanffy formulated the organismic system theory that later became the kernel of the GST (General Systems Theory]. GST is an interdisciplinary practice that describes systems with interacting components, applicable to biology, cybernetics, and other fields. Bertalanffy proposed that the classical laws of thermodynamics applied to closed systems, but not necessarily to "open systems," such as living things. His mathematical model of an organism's growth over time is still in use today.