Genesis 2:7 And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.
A living soul is that animation force in which the body moves and is directed to act in response to observation, understanding, reasoning, and desire. All living animals have a soul if they have a developed central nervous system. We can observe that in the actions of animals, and prolonged observation which bring about understanding to their particular nature, design and capability.
Animals can be singular in action, loners who have the highest level of selfish interests. Others can and do take on a communal personality, finding survival is served best in cooperative efforts. These animals have a form of communication which is not always understood by speech, but by posture, and actions. Some species develop complex communication skills which we can observe but only have an observers understanding.
Still other pack animals seem to be able to find a roll within the unit to serve the pack and seem to silently move in unison with the whole without any communication, as if they have a knowing which we have a hard time understanding.
Man however has developed the most complex soul functions. The mind of man, a function of the physical body, has developed the highest degree of complexity in observation and reasoning skills. The soul of man makes one distinction above that of animal and that is awareness of things greater than self-awareness. We seek our creator.
Now the soul is physically tied to the body in design. Without the living brain, the soul has no connection to the body. The soul is subject to the workings of the body, is aware of the bodies needs and desires, which are natural and without flaw. How the soul chooses to satisfy those needs and desires is however not determined by design intent but rather by selfish interests of the soul in reason and interests.
The body needs fuel but a steady diet of ice cream is not by design but rather selfish desire.