Why are biological systems called open?

Open biological systems are systems that are stable only if they continuously receive energy and substances from the environment and release them back into the environment.
Green plants use solar energy to synthesize the organic substances that make up their bodies. Other organisms receive energy as a result of the breakdown of complex organic substances of food into simpler ones. Thus, living organisms exist as long as they receive energy (solar or chemical) and nutrients from the outside.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.