Question

Why do biologists assign each organisms a universally accepted name?

Answer 1

So every organism is individually classified without the worry of mixing up two organisms like a fly and nat. 

Answer 2

It is important for scientists to assign a single scientific name to each organism so that people who speak different languages or dialects are not confused over different names for the same animal. Common names, such as dog or cat, can be misleading.

This might help: http://animaldiversity.org/animal_names/scientific_name/