Thermodynamics is a branch of physics that studies thermal energy and the principles of its distribution over the entire volume of a substance or a certain medium. This discipline is based on some general universal principles and uses the experimental data of many other sciences. Thermodynamic equilibrium is the cornerstone of this field of scientific knowledge.
One of the most important and, possibly, the most specific property of living organisms is their unique ability to convert energy and store it in a variety of forms. Thermodynamic equilibrium is a state of the system in which its parameters and characteristics cannot change over time without the influence of any external factors.
That is: a theoretically isolated physical system consisting of one or more physical objects can endlessly remain in a state of balance. If the thermodynamic equilibrium is disturbed, any system will tend to return to its stable state independently. This is one of the fundamental principles of physics, on which too much has been built both in our life and in nature.
It is easiest to imagine thermodynamic equilibrium by the example of such a natural human attribute as a thermos with hot tea, which is the very isolated system. Of course, the temperature at any point in the substance (in this case, tea) will be the same. But if you drop an ice cube into a thermos, the thermodynamic equilibrium will be immediately disturbed, since there will be a temperature difference in different parts of the liquid.
In this case, heat transfer will occur from the region of higher temperature in the direction of the colder sections, until the uniformity of the thermal regime is established in the entire volume. When this happens, stability will be restored. This is how any thermodynamic system works, regardless of its scale and the number of objects of which it consists.
The main condition for equilibrium, which is the same temperature indicator at all points of the system, is especially important for living organisms. All biological objects to maintain normal functioning require a regular supply of energy. All biological processes also need stable heat transfer and its uniform distribution.
For example, plants, accumulating solar energy, convert it into chemical bonds of organic substances through photosynthesis. In animals, everything happens exactly the opposite - organic substances obtained from food are converted into energy. All such processes (in representatives of both the plant and animal worlds) occur in strict accordance with the principles of the thermodynamic system.
The basic concepts of thermodynamics are universal and unshakable both for living biological systems and inanimate nature. The principles of thermodynamics say that any set of related objects can be called a thermodynamic system. The difference is only in the scale and number of objects. Examples of such systems are the cells of our body, the heart, or other internal organs. The whole organism is also in a sense a thermodynamic system. Even such gigantic objects as the biosphere, oceans also belong to this category. And they are subject to the same laws of thermodynamic equilibrium.