Why is it important for living things that ice is less dense than water

It is important because without ice being able to float Antarctica would be under water, resulting in water levels higher than they are now which then makes states like Florida and California (and all states that border the ocean) have less land than they do now.

It is called the medulla oblongata or people usually call it medulla. it is the lower half of the brain stem continuous with the spinal cord.