Ecological pyramids: upright or inverted?

• Food or energy relationships between trophic levels, drawn as bars, give a pyramid shape: broad at the base, narrow at the apex.
• The base stands for producers (first trophic level) and the apex for the top consumers.
• Three kinds are usually studied: the pyramid of number, of biomass and of energy.
• In a grassland, the pyramid of number shows only three top carnivores supported by the production of nearly 6 million plants.
• The pyramid of biomass usually falls sharply at higher trophic levels.
• In most ecosystems all three pyramids are upright: producers outnumber and outweigh herbivores, which outnumber and outweigh carnivores.
• Exceptions: counting the insects on one big tree, and then the small and larger birds that depend on them, gives an inverted pyramid of number.
• The pyramid of biomass in the sea is generally inverted: a small standing crop of phytoplankton supports a much larger biomass of zooplankton and fishes.
• The pyramid of energy is always upright and can never be inverted, because some energy is lost as heat at every transfer. Producers convert only about 1 per cent of the sunlight available to them into NPP.

Teaching this idea? Put the simulation on your own page or LMS with this code.