Final answer:
In a closed system, the total amount of energy remains constant due to the law of conservation of energy, although energy can change form within the system, typically increasing entropy overall.
Step-by-step explanation:
The total amount of energy in a closed system remains the same as per the law of conservation of energy. This is because in a closed system, energy cannot be created or destroyed. Examples of energy transfer within such a system include heat transferring from a high to a lower temperature, which generally increases the entropy of the system. Similarly, when energy is inputted into a living system, it can fuel catabolic reactions or decrease entropy within the system.
With regards to pressure and volume changes, when heat adds energy to a system, the pressure and volume of the system may both increase. However, this depends on the specifics of the system and the process conditions. For instance, adding a large amount of energy could also result in decreasing the volume and increasing the pressure if the system's capacity to hold energy is reached.