 In this short module, we are going to continue our discussion about dynamic systems within the context of their environment. Many types of systems require both a continuous input of resources from their environment and the capacity to export entropy back to the environment in order to maintain a specific level of functionality. An example of this might be a tractor that must receive a periodic input of fuel and be able to export heat and gases back to its environment for it to maintain its functionality. A business organization is another example requiring a continuous revenue stream to pay its employees and suppliers while also producing a certain amount of waste material that it must externalize and the same can be said of many other types of systems. Thus, in order for these systems to maintain their intended level of functionality, what we might call their normal or equilibrium state, they must have an environment that is conducive to providing them with these required conditions. Within ecology and biology, the term homeostasis is used to describe this phenomena. The word homeostasis derives from the Greek word meaning homos or similar and stasis meaning standing still. It is the state of a system in which variables are regulated so that internal conditions remain stable and relatively constant, despite changes within the system's environment. In order for systems to maintain homeostasis, there needs to be some kind of regulatory mechanism, what we also call a control system. This control mechanism has to regulate both the system's internal and external environment to ensure that the environmental conditions are within the given set of parameters that will enable the internal processes of the system to function at a normal or equilibrium state. Cybernetics is the area of systems theory that studies these regulatory mechanisms. Cybernetics again comes from a Greek word which means to steer or guide and this is exactly what a control system is designed to do. It is designed to guide the system in the direction of the set of environmental parameters that are best suited for it to maintain homeostasis. So let's take some examples of this. In order to maintain the environmental condition best suited to the physiology of a human being, we have invented the thermostat. Thermostats are classical examples of control systems that operate by switching heaters or air conditioners on and off in response to the information given by a temperature sensor. Thus, they regulate the environment in order to maintain a stable or equilibrium condition best suited to the internal workings of the human body. Another example might be the process control system in a chemical plant or oil refinery which maintains fluid levels, pressure, temperature and chemical composition within just the right parameters required for the desired chemical process to take place. There are many more examples of how adaptive systems maintain homeostasis but the essential characteristic of this phenomenon is to maintain a stable state conducive to performing a set of internal dynamic processes and this is done by monitoring information from feedback loops. If the system is in a homeostatic condition it will simply continue with its previous course of action but if one or more of the parameters it is designed to monitor are outside of these parameters it will perform some operation in order to affect the state of its environment. The control system then waits for a feedback of information from its environment in order to analyze how this previous activity has adjusted the desired parameters. Depending on whether this information signals the system moving away or returning to homeostasis it will again react accordingly. An example of this is a person driving a car. When we are cruising nicely along the road we simply continue doing what we have been previously doing whilst also continuing to monitor feedback loops but as soon as this information signals us approaching the limit of a homeostatic parameter such as getting too close to the side of the road we react by adjusting the steering wheel. We then wait a fraction of a second to monitor how this action has affected our status within the environment. Once this information is fed back to us and we have processed it we then once again react. All the time with the aim of returning to our desired homeostatic condition that enables the desired function of the car that is our transit from one location to another. We can then see how this concept of homeostasis can be a powerful model for capturing the development of any adaptive system as their course of development is the product of this continuous acting and reacting to feedback loops. Another thing we may note is how complex a system may become given two or more of these adaptive systems acting and reacting to each other's behavior as the system develops through an evolutionary like dynamic. We may also notice how this model captures a lot of dynamics underpinning the development of social systems such as international politics, free market economies and almost all types of social relations. But this is getting into a whole new area of complex adaptive systems that is the subject of another course.