MPPSC 2020 Prelims Paper-I · Question 87 of 100

Correct — A, always upright. The pyramid of energy is always upright, because at each higher trophic level a large part of the energy is lost (as heat in respiration), so the energy available decreases from producers upward. Unlike pyramids of number or biomass, it can never be inverted.

• (b)May be upright and inverted — Pyramids of number or biomass may invert, but the energy pyramid cannot — it is always upright.
• (c)Always inverted — Energy always decreases upward, so the pyramid is upright, never inverted.
• (d)None of the above — The correct description — 'always upright' — is available as option (a).

Energy flow in an ecosystem is one-way and diminishing: only about 10% of energy passes to the next trophic level (the '10% law'). Because energy is lost at each step, the pyramid of energy is invariably upright.

Contrast the three ecological pyramids: number and biomass can invert (e.g. a tree supporting many insects; ocean plankton), but energy cannot. Always upright = pyramid of energy.

• Energy pyramid: producers at the base hold the most energy.
• Roughly 10% of energy transfers to each higher trophic level ('10% law').
• Energy is lost as heat in respiration at every level.
• Pyramids of number/biomass may invert; the energy pyramid never does.

• Thinking the energy pyramid can invert like number/biomass pyramids
• Confusing the three pyramid types

Concept recall — pyramid of energy is always upright.

No directly related past PYQ was found.

• practice — not a real PYQ

  Roughly what fraction of energy is transferred to the next trophic level ('10% law')?

  • (a)About 10%
  • (b)About 50%
  • (c)About 90%
  • (d)About 1%

  Answer(a) About 10%.

• practice — not a real PYQ

  Which ecological pyramid can sometimes be inverted?

  • (a)Pyramid of biomass
  • (b)Pyramid of energy
  • (c)Neither
  • (d)Only the energy pyramid

  Answer(a) Pyramid of biomass (and of number).