Q.Justify the statement, ''Pyramid of energy is always upright, and can never be inverted.''
You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.
Start your 14-day free trial to unlock the full solution →Energy pyramids are always upright because energy transfer between trophic levels obeys the second law of thermodynamics—each level loses most energy as heat, so producers must always contain more energy than herbivores, herbivores more than carnivores, and so on.
The pyramid of energy represents the amount of energy present at successive trophic levels in an ecosystem at a given time. Unlike pyramids of number or biomass, which can sometimes be inverted depending on the ecosystem, the energy pyramid maintains a consistent upright shape across all ecosystems—terrestrial, aquatic, forest, grassland, without exception. This universality stems from fundamental physical laws governing energy flow.
When sunlight strikes a green plant, only about 1–2% of that solar energy is captured through photosynthesis and converted into chemical energy stored in organic compounds. This is the base of every food chain. Now, when a herbivore eats that plant, it does not receive all the energy the plant stored. A substantial portion—roughly 90%—is lost. Some energy was already used by the plant for its own respiration, growth, and maintenance. Some remains locked in parts the herbivore cannot digest (cellulose in cell walls, for instance). Some is lost as heat during metabolic processes in the herbivore's body.
The herbivore, therefore, receives only about 10% of the energy that was present in the plant tissue it consumed. This is the famous "10% law" articulated by Raymond Lindeman. When a carnivore preys on that herbivore, the same principle applies—another 90% loss, another 10% transfer. Each step up the food chain sees this dramatic energy drain.
The second law of thermodynamics dictates that every energy transformation involves loss of usable energy as heat. Biological systems cannot escape this law—energy flows one way through an ecosystem and steadily dissipates.
Because of this unavoidable energy loss at each trophic level, the amount of energy available must decrease as we move from producers to primary consumers to secondary consumers to tertiary consumers. Mathematically and physically, it is impossible for a higher trophic level to contain more energy than the level below it. You cannot get more energy out of a system than you put into it.
Consider why pyramids of number and biomass can be inverted. In a forest, one large tree (small number) supports thousands of insects (large number)—an inverted pyramid of numbers. In an ocean, the biomass of phytoplankton at any instant might be less than the biomass of fish feeding on them, because phytoplankton reproduce so rapidly that their total productivity over time is enormous even if their standing crop is small—a partially inverted biomass pyramid. But energy? Energy is not stored and accumulated over time in the same way. It flows through and dissipates. The energy passing through phytoplankton in a year is always greater than the energy passing through the fish that eat them, even if the fish outweigh the phytoplankton at a snapshot in time. …
Unlock everything free for 14 days
- Full step-by-step solutions
- Concept-first explanations
- Methods, shortcuts & mistakes
- PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.