Who owns the dog?

The man. The tick is just a parasite with no concept of ownership.

One could argue then that the dog, too, is a parasite of man since it also derives its food from us, but this is not quite accurate, since we also derive something from dogs--love and companionship. Therefore it would be more accurate to say that dogs and humans are in a symbiotic relationship.

The tick contributes nothing of value to the dog, so it is purely parasitical.

Ownership, first lets assume such a thing, as the question is gesturing us to assume. It may be a trick question but what the hey.

By my conventions and beliefs the Man owns the dog because he bought it (if we assume that he did). If he did not buy it, he owns it because he looks after it (by feeding it).

If we want a more radical answer, we could say the man does not own it because its just a convention not a truth. However it can be argued that the concept of ownership is a convention by definition, so this truth business is irrelevant.

The tick is just a free loader(taking blood or what ever ticks do on dogs) who doesn't have ownership of the dog. I suppose if you want to take the Ticks point of view, you could say they own it, but I don't think they have the rational or thinking capabilities for it. I'm saying ownership is a belief convention, so this is the case.

The concept of ownership is a territorial construct best elucidated by George Carlin in his famous treatise on "stuff." If you have not read it I recommend "Brain Droppings". Although a dog may not fall into the category of "stuff" I still believe that the human would in fact be the only entity capable of understanding the concept of owner.

The tick, on the other hand, is a parasite.

As the man pays for the food and the tick eats for free I suppose the man does...but try telling my dog that!

The man that feeds it for in so owning the dog, the man also can get ride of the tick, KILL it. As I do, so I own my dog and I kill that sucker flea.

I forget who, but your question reminds me of a salient observation by some comedian who asked, who's in charge, the dog being walked or the person following and picking up the poo?

Neither, the dog owns himself. That he consents to be fed, and bears the tick is choice.

definitely the man

The supplier of nurishment.

no one owns him, dogs own the world and we just live in it.