Final answer:
The total weight of the glass box and its contents likely increased because the tree absorbs carbon from the air through photosynthesis and converts it into organic material, thus adding mass to the system.
Step-by-step explanation:
Considering the scenario provided with a tree growing inside a glass box with a water supply and fertile soil, the total weight of the box and its contents likely increased. This increase is due to photosynthesis, whereby the tree absorbs carbon dioxide from the air and, using sunlight, converts it into organic material and oxygen. Most of the mass of the growing tree comes from carbon, which is derived from carbon dioxide, not the soil or the initial seed mass.
The hypothesis here is that as the tree grows larger through the process of photosynthesis, pulling in carbon from the CO2 in the atmosphere, the overall mass of the system (tree plus the box) will increase. Soil contributes a minor amount to the overall plant mass, as studies show that even when dry, plant matter retains significant mass. Therefore, the plant's growth predominantly adds to the total weight through carbon absorption.