Terrarium and Earth Comparison A terrarium is a simple example of an organized group of parts that work together to form a whole. To understand a system, you need to see how all its parts work together. What are the parts of Earth’s system and what are the matching parts in the terrarium? Both a terrarium and Earth are closed systems. What does it mean when it says they are a closed system? The system may be closed, but energy can flow into or out of the system. Explain how this happens in the terrarium and on Earth. The Biosphere 2 is a giant example of a terrarium. Explain what went wrong with the initial experiment and how that could be important knowledge if you were setting up your own terrarium. Within Earth’s system there are four connected parts. Each of these parts is an open system because both matter and energy move into and out of it. The four open systems work together to form one large, closed system called Earth. How do these parts work together? Look closely at this terrarium. Notice that the bowl and its cover form a boundary between the terrarium and the outside world. What might happen to the entire terrarium if any part were taken away? What might happen if you placed the terrarium in a dark closet? How are either of those questions relevant to Earth? How is the possibility of people living on Mars and giant terrariums related?