Tree falls in a forest...

Haven't posted in a while so I thought I would finally raise a philosophical issue. I'm reading George Berkeley right now for a class and like every other philosopher he's addressing the problem of senses - more specifically how easily they can be deceived.

So here's the question in many forms: Does an object need to exist before it can be perceived? Or can it be said to exist only after it has been perceived?
What if all of mankind has died out- does the physical universe still exist? What about the concept of "odor"? Does it exist if no one with a nose is around?

Update: If a post gets no comments does it mean no one read it? It is so ironic that as I question whether something needs to be perceived to exist, seemingly no one has perceived my question. Well my question does exist on this server so lets say it's been answered and move on.