You will lose a pound if you burn 3500 more calories than you take in. This is one of the bottom lines in weight loss but whether or not you are actually burning 3500 calories varies from person to person with the same activity.
A dog can survive without eating for 14 days, procided day wouldn't be in good shape and health.
The question of how long you can go without food depends on a lot of factors. Will and determination definitely play a part. Political prisoners on hunger strikes and fasting religious leaders have been known to go for weeks at a time without any food. Gandhi fasted for 21 days while in his 70s. People lost in the wild have also survived for long periods of time without eating. Medically speaking, most doctors agree that healthy humans can go up to eight weeks without food as long as they have water. People have gone longer and been fine, and people have starved to death in less time. Being strong and in good physical shape can help you survive longer, but so does having extra body fat.