2. Identify each of the following as either an open, closed, or isolated system: a. Reef ecosystem:
b. Nitrogen cycle:
c. Earth:
d. Biosphere:
e. Solar system:
f. Digestive system:
g. A national park:
h. A large lake:

the answer to your question is tooth decay.

maybe because its impossible for balloons to lift a whole entire house.

only about ten percent of the energy at one trophic level is passed on to organisms at the next trophic level. the remainder of the energy is used in life processes or lost as heat.