Week 1 - Human Body Is A Living System

A living system can be big or small. Our planet Earth is a living system, and a single cell is also a living system. What, in deed, is a living system? A living human body has a composition of all the biochemical  elements, such as carbon, hydrogen, oxygen, phosphate, nitrogen, sulfur, etc., which are making connections and reactions according to Laws of Physics, is that enough to define a living system?

The descriptive definition of life has been a challenge since life is process not a substance, and our knowledge of life is limited to the known living entities on planet Earth. Life has most or all of the following characters:

A living system has a capability to store, retrieve, transmit, and respond to information essential to life processes, such as being able to maintain homeostasis, regulating the internal environment to maintain a constant state. A living human body is able to regulate the internal temperature according to external environmental changes. 

https://sites.google.com/site/rosecransclassroom/homeostasis

A living system is organized in a structured way and has the capability of transforming energy. A living human body is composed by organized cellular structures, and it requires energy to maintain internal organization and to produce other phenomena associated with life.

A living system can grow, adapt, and reproduce. A living body can grow cells in size and numbers, be able to response to the environment and stimuli, and be able to reproduce its own cells as well as new individual organisms. 

According to living system theory, a living thing is an open self-organizing system that interact with the environment. Such system is maintained by flows of information, energy, and matter. In 1974, Varela, Maturana, and Uribe proposed that living beings are autopoietic systems that can reproduce and maintain itself. 

https://www.sciencedirect.com/science/article/pii/0303264774900318