C. Ecological Pyramids 1. Trophic structure can be diagrammed as a pyramid in which producers form a base for successive tiers of consumers above them. A pyramid of biomass makes provision for differences in size of organisms by using the weight of the members in each trophic level. A pyramid of energy reflects the trophic structure most accurately because it is based on energy losses at each level. An Overview A. Biogeochemical cycles influence the availability of essential elements in ecosystems.
Elements are available to producers as ions.
Nutrient reserves are maintained by environmental inputs and recycling activities. The amount of nutrients being cycled is greater than the amount entering or leaving. Environment inputs are by precipitation, metabolism, and weathering. Outputs are by runoff and evaporation. In the hydrologic cycle, oxygen and hydrogen move as water molecules.