The type of diagram used to show the flow of energy in an ecosystem is called a food pyramid or a trophic pyramid. These diagrams illustrate the distribution of energy across different trophic levels, from producers at the base to top-level consumers at the apex. Each level represents a specific group of organisms in the food chain, highlighting the decrease in available energy as it moves up the pyramid. By using a triangular structure, these diagrams visually demonstrate the energy transfer efficiency and the interconnectedness of various species within the ecosystem.