For a fish to be buoyant, or float, it must displace less water or the same amount of water as its own body mass. ... Many fish use swim bladders to help them with quick depth changes. These bladders fill with air to help fish rise or release air so fish can sink, often in conjunction with forward movement.
For the answer to the question above, the peripheral nervous system governs <span>all structures outside the brain and spinal cord. Peripheral nerves branch from the spinal cord through the foramen transversarium of each vertebrae. I suppose the structure it would not affect is the brain itself since cranial nerves are responsible for brain activity. Also, the spinal cord would also be unaffected since it is just a cylindrical bundle of nerve fibers that allow the connection of the peripheral nerves to the brain.</span>
Answer:
In a comparison of birds and mammals, the condition of having four limbs is a shared ancestral character
