ENERGY can enter a biological system from only a few sources called primary producers:
Algae can harness light energy and convert it to new biomass through a process called PHOTOSYNTHESIS. The new biomass has a energy density that is ~70% of coal (lots of energy). That density of energy makes it a target for predators. A grazer is a consumer of primary producers.
The copepods are found in nearly all aquatic environments from the oceans to lakes and streams. They serve as a conduit to transfer energy from primary producers to other heterotrops (organisms that eat other organisms). Copepods along with other small grazers are are the basis of trophic energy transfer to the macro-organism that we all love.