Human Body - Open or Closed?

     Open or Closed?  - TERRARIUM

POND - Open or Closed?    

Which is open? Which is closed? Why?

    You probably have guessed that the first picture, the one of the terrarium, is closed. Why? Because, as the plastic bubble surrounds it, matter is prevented from entering or exiting, but energy (such as heat, sunlight) can still penetrate the dome. However, a system doesn't need to have a restricting dome over it to be a closed system. Anything as simple as a swimming pool is a closed system. 
    The second picture, the one of the pond, is an open system. This means the both energy and matter can get in and out of the system. Whether this is by animals going in and out or simply human interaction, the pond is definitely an open system based on the number of matter and energy interactions that occur.

So what type is system is the human body? 

    The human body is an open system. Various inputs such as oxygen, food, and water are inputs whereas waste and carbon dioxide are outputs. Energy can also be transmitted in and out of the system, for example if one is throwing a ball, kinetic energy is passed from a human's hand to a ball, thus the exchange of energy. The human body can not be a closed system because that would require no food to be able to go in or out of the system, meaning nothing could be eaten, and no energy to go in and out, meaning that energies such as heat could not be transmitted, nor given off, ultimately leading to death.