What does organisms have to respond to stimuli? How is the regulation of body functions?

Due to irritability, organisms have the ability to adapt. Adaptation is understood as the process of adaptation of an organism to certain environmental conditions.
This is achieved by regulation, carried out in all organisms with the help of chemicals, and in multicellular animals also thanks to nerve impulses coming from the organs of the nervous system.

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.