A trophic level represents a step in the dynamics of energy flow through an ecosystem. The first trophic level is made up of the producers, those within the ecosystem that harvest energy from an outside source like the sun (or deep-sea thermal vents) and stabilize or “fix” it so that it remains in the system and is accessible to others within the system. The second level would comprise those who consume the producers, also known as the primary consumers. The next level would contain the secondary consumers (those who consume the primary consumers), and so on. Because of the limited amount of energy available to each level, these trophic pyramids rarely rise above a third or fourth level of structure. R. Lindeman (1915–1942) was one of the first ecologiste to refer to the “trophic dynamics” of ecosystems, doing so in 1942.