How can DNA profiling be used to determine the number of organisms from a specific species that is within a certain area?
The general process of DNA profiling (I prefer calling it "DNA fingerprinting", but that's just me) generally involves developing PCR primers specific for a particular region surrounding some sort of highly polymorphic region. So in this case one would need primers surrounding VNTRs (or other polymorphic regions, have a look at the wikipedia article for an overview of some other methods). Presuming the PCR primers are specific for bears (one could blast them to get an idea of this), then regardless of what other animals were mixed in, the resulting bands would predominantly be from bears (after all, PCR results in an exponential amplification of favored species). This would be answer part (1).

For part 2, one needs to find a sufficient number of sufficiently variable regions for profiling to work. A single site might not be informative enough, but a couple of them together will be.

Part 3 is the logical outcome of parts 1 and 2. If you can amplify a bunch of mixed samples together and the repeats are of variable length (thus the use of VNTRs or similar repeats), then you'll see those as different sized bands on a gel.