In
ecology,
trophic dynamics is the system of
trophic levels (
Greek t??f?,
trophe, food or feeding), which describe the position that an organism occupies in a
food chain — what an organism eats, and what eats the organism.
Most ecosystems ultimately rely upon the Sun for energy and upon photosynthetic organisms to harness that energy. There are only a few exceptions to this, such as chemosynthetic archaea which derive energy from the break down of sulfur rich compounds around deep sea hydrothermal vents and acid mine drainage.
In terrestrial ecosystems, plants such as grass are the primary producers and form the first trophic level. Next are herbivores (primary consumers) that eat the grass, such as rabbits. Next are carnivores (secondary consumers) that eat the rabbits, such as a bobcat.
Every time there is an exchange of energy between one trophic level and another, there is quite a significant loss due to the fundamental laws of thermodynamics. This means so many units of grass can only support a much smaller number of units of rabbits, who can only support a smaller group of bobcats, who can only support a smaller group of mountain lions. This is why trophic levels are usually portrayed as a pyramid, one that places grass on the bottom and mountain lions on top—the top is always much smaller than the bottom. Each level implies a loss of energy and efficiency and less life that can be supported by the sun.
