In the trophic structure, classification of organisms in an ecosystem occurs through the energy source and consumption of food by an organism. The trophic structure represents the relationship between species and food sources.
Scientists place organisms into levels, though some organisms cross more than one level. The categorization of food sources is from the hierarchy of the food chain. As trophic levels increase, the energy that organisms require for food consumption decreases. The extinction or vast reduction of a species changes the structure. The groups break down into producers, consumers and decomposers. Within each group, there is a level contingent upon the consumer group.