Once food has reached the sea floor, currents carry this food and organisms filter it without having to use their own energy to go and get food. Another way organisms use energy is by coming out at night and rising to feed on upper-level organisms.
Physical Science redirects here. It is not to be confused with Physics. Physical science is a branch of natural science that studies non-living systems, in contrast to life science. It in turn has many branches, each referred to as a physical science, together called the physical sciences.
Physical science is basically an umbrella term for the natural sciences that don't deal with living things or systems. We generally contrast physical science with the biological sciences. As we look at the sciences, we see many fields, such as biochemistry, where the biological and the physical sciences overlap.