Note: “planetary wear” refers to outfits which might be needed when visiting a planet with a breathable atmosphere, where a spacesuit is not necessary — for example, rainwear or scuba gear for Terra or Venus, or cold-weather gear for Mars or parts of Terra.
The biosphere is a special wing filled with a self-contained, self-sustaining Terran ecology — basically a nature preserve, including animals, trees and other plants, ponds, etc. It not only helps to recycle the station’s atmosphere [just as Earth’s air is recycled by its own ecosystem]: it also serves as a relaxation/recreation area for the team, not to mention providing opportunities for observation and study for Doc‘s research.
(The gates are specially built entryways designed to prevent wildlife from escaping into the rest of the station.)
For more info about utilities and shielding, see here.