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 an encompassing term for the branches of natural science and science that study non-living systems, in contrast to the life sciences. However, the term physical creates an unintended, somewhat arbitrary distinction, since many branches of physical science also study biological phenomena.