Well, for one, a dogs nose has 300 million olfactory receptors in their noses, whereas humans only have 6 million. Dogs primarily go about their life relying on their noses, whereas an animal such as a alligator may rely more on its sight. Animals like a snake rely on heat pits that line their upper lips to find food, and when eating they have a second nose called the glottis. About the dog again, a dogs hearing is WAY more sensitive than ours, they can hear sounds up to four times farther than we can, and are able to recognize the sound of your car and are able to pin point minuscule sounds like its nothing. Not to mention they can also hear many different frequency of sounds than we can. An animals senses are everything to its survival, if they didn't have the recourse and senses they have now, living in the wild or just everyday life would be incredibly harder for them.