Part 8 – Pyramids of Energy
Part 8 – Pyramids of Energy (Always Upright, Ecological Significance)
(25 MCQs with answers and detailed explanations, NCERT Class 12 + NEET UG level)
Q1.
The pyramid of energy is always:
a) Upright
b) Inverted
c) Cylindrical
d) Irregular
Answer: a) Upright
Explanation:
Energy decreases with each trophic transfer → cannot be inverted.
Q2.
Which law explains why the energy pyramid is always upright?
a) Hardy–Weinberg law
b) Lindeman’s 10% law
c) Gause’s law
d) Law of limiting factors
Answer: b) Lindeman’s 10% law
Explanation:
Only ~10% of energy passes to next trophic level.
Q3.
In an energy pyramid, energy flow is:
a) Bidirectional
b) Cyclic
c) Unidirectional
d) Random
Answer: c) Unidirectional
Explanation:
Sunlight → producers → consumers → lost as heat, not recycled.
Q4.
Which ecological pyramid best reflects the functioning of ecosystems?
a) Pyramid of number
b) Pyramid of biomass
c) Pyramid of energy
d) All equal
Answer: c) Pyramid of energy
Explanation:
Shows actual energy transfer and is always upright.
Q5.
In a pyramid of energy, the base represents:
a) Herbivores
b) Producers
c) Carnivores
d) Decomposers
Answer: b) Producers
Explanation:
Energy enters ecosystem via producers at the base.
Q6.
Why can energy pyramids never be inverted?
a) Producers always have maximum energy
b) Energy is lost as heat at each transfer
c) Energy is not recycled
d) All of the above
Answer: d) All of the above
Explanation:
Energy input is highest at base and decreases at higher levels.
Q7.
In an ecosystem with 10,000 kcal at producer level, energy available to primary consumers is:
a) 100 kcal
b) 1000 kcal
c) 10 kcal
d) 5000 kcal
Answer: b) 1000 kcal
Explanation:
10% of 10,000 kcal → 1000 kcal to herbivores.
Q8.
Energy pyramids are expressed in:
a) kcal/m²/year
b) g/m²
c) Number of organisms
d) Tons of biomass
Answer: a) kcal/m²/year
Explanation:
Measured as rate of energy flow per unit area per unit time.
Q9.
Who introduced the concept of energy flow in ecosystems?
a) Lindeman
b) Odum
c) Elton
d) Tansley
Answer: a) Lindeman
Explanation:
Raymond Lindeman (1942) → energy flow studies in Cedar Bog Lake.
Q10.
Energy transfer efficiency between trophic levels is typically:
a) 1%
b) 5%
c) 10%
d) 50%
Answer: c) 10%
Explanation:
On average, ~10% of energy is passed upward.
Q11.
Which pyramid can never be inverted in any ecosystem?
a) Number
b) Biomass
c) Energy
d) None
Answer: c) Energy
Explanation:
Due to unidirectional loss of energy.
Q12.
Energy decreases at higher trophic levels because of:
a) Heat loss during respiration
b) Incomplete assimilation
c) Excretion
d) All of the above
Answer: d) All of the above
Explanation:
Multiple pathways cause energy loss at each transfer.
Q13.
Which is the most reliable pyramid for comparing ecosystems?
a) Number pyramid
b) Biomass pyramid
c) Energy pyramid
d) All equal
Answer: c) Energy pyramid
Explanation:
Energy pyramids always upright and depict functional efficiency.
Q14.
If secondary consumers receive 100 kcal, energy at producer level was:
a) 1000 kcal
b) 10,000 kcal
c) 100 kcal
d) 1,000,000 kcal
Answer: b) 10,000 kcal
Explanation:
Producers (10,000) → herbivores (1000) → secondary consumers (100).
Q15.
In energy flow, decomposers obtain energy from:
a) Sunlight
b) Dead organic matter
c) Herbivores
d) Carnivores
Answer: b) Dead organic matter
Explanation:
Decomposers recycle matter by feeding on detritus.
Q16.
Why are energy pyramids better than biomass pyramids?
a) Never inverted
b) Show actual energy transfer
c) Represent ecosystem function
d) All of the above
Answer: d) All of the above
Explanation:
They avoid misleading results and always upright.
Q17.
At each trophic level, most energy is lost as:
a) Fecal matter
b) Respiration heat
c) Excretion
d) Biomass storage
Answer: b) Respiration heat
Explanation:
Respiration → major energy loss pathway.
Q18.
Which ecosystem has the highest energy fixation rate per unit area?
a) Desert
b) Grassland
c) Tropical rainforest
d) Tundra
Answer: c) Tropical rainforest
Explanation:
Warm, moist conditions → maximum productivity.
Q19.
Energy captured by producers but lost in respiration is part of:
a) GPP
b) NPP
c) Secondary productivity
d) Standing crop
Answer: a) GPP
Explanation:
GPP includes total energy fixed before respiration losses.
Q20.
Energy available to herbivores in an energy pyramid is:
a) GPP
b) NPP
c) Respiration
d) Secondary productivity
Answer: b) NPP
Explanation:
NPP = energy available to consumers.
Q21.
Which statement is TRUE about energy flow?
a) Energy can be recycled
b) Energy flow is unidirectional
c) Energy is conserved across trophic levels
d) All energy reaches top carnivores
Answer: b) Energy flow is unidirectional
Explanation:
It moves one-way and is lost as heat.
Q22.
Top carnivores receive approximately how much energy of producers?
a) 0.1%
b) 1%
c) 10%
d) 50%
Answer: a) 0.1%
Explanation:
10% law → 10,000 → 1000 → 100 → 10 kcal (0.1%).
Q23.
Pyramid of energy best illustrates:
a) Biomass distribution
b) Energy loss between trophic levels
c) Population size
d) Nutrient cycling
Answer: b) Energy loss between trophic levels
Explanation:
It clearly shows energy decline at each step.
Q24.
What limits the length of energy pyramid?
a) Nutrient cycles
b) Energy loss at each transfer
c) Reproductive rate of producers
d) Presence of decomposers
Answer: b) Energy loss at each transfer
Explanation:
Chains rarely exceed 4–5 trophic levels.
Q25.
Energy pyramids highlight the principle that:
a) Energy transfer is 100% efficient
b) Energy decreases at higher levels
c) Decomposers produce energy
d) Biomass is constant
Answer: b) Energy decreases at higher levels
Explanation:
Due to respiration and heat loss.
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