Biology
Energy Pyramid
Quick fact
The 10% rule means that to gain 1 kilogram of body mass, a top predator like a lion requires about 10,000 kilograms of grass (through the food chain).
Why this is interesting
You eat a burger for lunch, but where does all that energy actually go? Surprisingly, only about 10% of the energy from the cow's grass makes it into your meal.
Read the full explanation
Understanding Energy Pyramid
An energy pyramid is like a stack of blocks, each block representing a trophic level—a step in the food chain. The bottom layer consists of producers (plants and algae) that capture sunlight through photosynthesis. Above them are primary consumers (herbivores) that eat the plants, then secondary consumers (carnivores) that eat herbivores, and so on. With each step, most of the energy is used for the organism's own life processes (movement, growth, reproduction) and lost as heat. Only a small fraction, roughly 10%, is passed on to the next level. This is why each layer of the pyramid is smaller than the one below it. You can picture it as a game of pass-the-parcel where each person keeps most of the prize before handing a tiny piece to the next.
A deeper explanation
The energy pyramid's shrinking shape is a direct consequence of the second law of thermodynamics: energy transfers are inefficient because some energy always dissipates as heat. In biological terms, organisms are not perfect at converting food into new biomass. Most ingested energy is spent on cellular respiration (maintaining body temperature, muscle contraction, nervous activity) or is excreted. This energy cannot be recycled by the same food chain—it leaves the ecosystem as heat. The pyramid concept matters because it explains critical ecological patterns: why there are far fewer predators than prey, why food chains rarely exceed four or five levels, and why humans get more energy by eating plants directly (as in a vegetarian diet) rather than by consuming animals higher up the pyramid. It also helps in designing sustainable fisheries, managing wildlife populations, and understanding the impact of removing top predators.