Question

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In a food pyramid, there is typically less biomass at the top (i.e., there are very few individual tertiary consumers,
whereas there are numerous individual producers). In three to five sentences, explain this phenomenon, citing
evidence relating to energy flow and how plants support ecosystems. (4 points)

B

Answer 1

Plants (primary producers) capture solar energy by photosynthesis and convert it into chemical energy that fuels all other trophic levels. Because energy is lost at each step to respiration, maintenance, movement and heat, typically only about 1–20% (commonly ~10%) of the energy at one trophic level is incorporated into the next. As a result there is much more biomass in producers than in herbivores, and much less biomass in top predators: less available energy means fewer individuals can be supported at higher levels. This energy-flow constraint explains the narrow top and wide base of food pyramids.