As you go up the trophic levels, biomass decreases, which explains why there is less biomass at the top of a food pyramid. Through a process called photosynthesis, producers like plants transform solar energy into usable energy. Mostly because of respiration and other metabolic processes, they lose energy, so only a small amount of that energy is stored in their tissues. Since energy is lost during metabolism, herbivores only retain about 10% of the energy from the plant when they eat it. When herbivores are eaten by carnivores, the same thing happens.
This energy loss continues as you move up the trophic levels, resulting in less biomass being present at each level. At the top of the food pyramid, there is not enough energy remaining to support a large population of organisms, which is why there is less biomass at the top compared to the bottom. This also explains why there are usually fewer top predators in an ecosystem, as there is simply not enough energy available to support a large population of them.
Additionally, as you move up the trophic levels, there is also a decrease in the efficiency of energy transfer. This means that more energy is lost as heat or in other metabolic processes as you move up the food chain. This contributes to the lower biomass at higher trophic levels.
Overall, the concept of energy flow through an ecosystem helps to explain why there is less biomass at the top of a food pyramid. This natural inefficiency in energy transfer plays a key role in shaping the structure and dynamics of ecosystems.