__10% Rule __
Approximately 10% of the energy “harvested’ at a lower tropic level is transferred up to the next higher tropic level.
Organisms such as bacteria, earthworms, and fungi are heterotrophic organisms that obtain nutrition by feeding on dead, decomposing organic plant and animal matter and helping recycle nutrients.
Organisms such as cyanobacteria, phytoplankton, and plants encompass the first trophic level. They are autotrophs; they prepare their food by photosynthesis by utilizing radiant energy from the sun.
The second trophic level includes herbivores such as rabbits, sheep, and cows that consume the producers and their products to gain energy.
The third trophic level is occupied by the primary carnivores or meat eaters and omnivores such as snakes and bears that eat the herbivores.
The fourth trophic level is occupied by the secondary carnivores and omnivores that eat the primary carnivores. Examples of tertiary consumers include hawks and turtles.
Eagles, sharks, and alligators, along with us humans, comprise quaternary consumers. It includes predators who eat a lot of prey but are usually not preyed upon themselves.