F2.8 Vs. F16

1. What part of the body should we closely relate aperture: Are pupil because that is the part of the body that i guess focuses or you see out of.
2. Finish this sentence - the smaller the Aperture OPENING, the higher the Aperture NUMBER.
3. In your own words tell me how aperture impacts Depth of Field? The size of the aperture has a big affect of the depth of field.