Part 7 – Pyramids of Biomass
Part 7 – Pyramids of Biomass (Terrestrial Upright, Aquatic Inverted)
(25 MCQs with answers and detailed explanations, NCERT Class 12 + NEET UG level)
Q1.
The pyramid of biomass in a terrestrial ecosystem (e.g., forest, grassland) is generally:
a) Upright
b) Inverted
c) Cylindrical
d) Irregular
Answer: a) Upright
Explanation:
Producers (large biomass) → herbivores (less) → carnivores (least).
Q2.
The pyramid of biomass in an aquatic ecosystem is usually:
a) Upright
b) Inverted
c) Cylindrical
d) Irregular
Answer: b) Inverted
Explanation:
Phytoplankton biomass is less than zooplankton biomass at a given time.
Q3.
In a forest ecosystem, the biomass of producers is:
a) Less than herbivores
b) Greater than herbivores
c) Equal to carnivores
d) Negligible
Answer: b) Greater than herbivores
Explanation:
Plants (trees) form huge standing biomass compared to herbivores.
Q4.
In aquatic ecosystems, phytoplankton biomass is small because:
a) They are heavily grazed but reproduce very fast
b) They are large in size
c) They cannot photosynthesize
d) They lack nutrients
Answer: a) They are heavily grazed but reproduce very fast
Explanation:
Small standing crop but high productivity turnover.
Q5.
Which ecosystem shows inverted biomass pyramid?
a) Forest
b) Grassland
c) Pond
d) Desert
Answer: c) Pond
Explanation:
Aquatic ecosystems often show inverted biomass pyramids.
Q6.
Standing crop is measured in terms of:
a) Energy
b) Biomass or number per unit area
c) Nutrient concentration
d) Oxygen content
Answer: b) Biomass or number per unit area
Explanation:
Expressed as g/m² or kcal/m².
Q7.
What is the main reason for inverted biomass pyramids in aquatic systems?
a) Producers reproduce slowly
b) Herbivores are absent
c) Producers are small but have high turnover
d) No decomposers present
Answer: c) Producers are small but have high turnover
Explanation:
Phytoplankton biomass small but replaced rapidly.
Q8.
Which of the following shows upright pyramid of biomass?
a) Grassland ecosystem
b) Aquatic ecosystem
c) Pond ecosystem
d) Open ocean
Answer: a) Grassland ecosystem
Explanation:
Large plant biomass at base.
Q9.
In an inverted biomass pyramid, which trophic level may temporarily exceed producers?
a) Primary consumers
b) Secondary consumers
c) Tertiary consumers
d) Decomposers
Answer: a) Primary consumers
Explanation:
Zooplankton biomass can exceed phytoplankton at a given instant.
Q10.
Which unit is used for measuring biomass pyramids?
a) kcal/m²
b) kcal/m²/yr
c) g/m² or kcal/m²
d) kg per year
Answer: c) g/m² or kcal/m²
Explanation:
Standing crop measured as weight (dry mass) or energy equivalent.
Q11.
In which ecosystem is herbivore biomass sometimes greater than producer biomass?
a) Forest
b) Desert
c) Pond
d) Grassland
Answer: c) Pond
Explanation:
Aquatic → zooplankton biomass > phytoplankton biomass at a time.
Q12.
Which of the following is a limitation of biomass pyramids?
a) May be inverted in aquatic systems
b) Ignores productivity rate
c) Doesn’t represent energy flow accurately
d) All of the above
Answer: d) All of the above
Explanation:
Biomass pyramids don’t always reflect real energy dynamics.
Q13.
In a terrestrial ecosystem, herbivore biomass is:
a) Always greater than producer biomass
b) Always smaller than producer biomass
c) Equal to producer biomass
d) Independent of producers
Answer: b) Always smaller than producer biomass
Explanation:
Plants always outweigh herbivores in biomass.
Q14.
The inverted biomass pyramid in oceans is due to:
a) Low phytoplankton productivity
b) Small size & rapid turnover of phytoplankton
c) Absence of producers
d) Absence of decomposers
Answer: b) Small size & rapid turnover of phytoplankton
Explanation:
Phytoplankton reproduce rapidly but standing crop is low.
Q15.
Standing crop of biomass at a trophic level is measured at:
a) One instant of time
b) Whole year average
c) After decomposition
d) After nutrient cycles
Answer: a) One instant of time
Explanation:
Standing crop = biomass at a given time.
Q16.
Which ecosystem has the maximum standing biomass?
a) Grassland
b) Tropical rainforest
c) Desert
d) Ocean
Answer: b) Tropical rainforest
Explanation:
Huge vegetation stock → high biomass.
Q17.
In aquatic systems, the biomass pyramid is inverted because:
a) Producers are absent
b) Consumers eat producers faster than they reproduce
c) Decomposers dominate
d) Top carnivores are more
Answer: b) Consumers eat producers faster than they reproduce
Explanation:
But phytoplankton reproduce quickly, sustaining system.
Q18.
Biomass pyramids in terrestrial ecosystems usually resemble:
a) Upright triangles
b) Inverted triangles
c) Hourglass
d) Cylinders
Answer: a) Upright triangles
Explanation:
Large base (plants), narrow top (carnivores).
Q19.
The inverted pyramid of biomass was first observed in:
a) Forest ecosystem
b) Pond ecosystem
c) Grassland ecosystem
d) Ocean ecosystem
Answer: d) Ocean ecosystem
Explanation:
Zooplankton outweigh phytoplankton biomass.
Q20.
Which trophic level has least biomass in upright biomass pyramid?
a) Producers
b) Primary consumers
c) Secondary consumers
d) Tertiary consumers
Answer: d) Tertiary consumers
Explanation:
Least energy transfer upward → smallest biomass.
Q21.
Why are biomass pyramids more accurate than number pyramids?
a) They ignore energy content
b) They consider organism size and mass
c) They are always upright
d) They show species richness
Answer: b) They consider organism size and mass
Explanation:
Tree (one producer) has huge biomass compared to many insects.
Q22.
What is the major drawback of biomass pyramids in aquatic systems?
a) They ignore energy flow
b) They can be inverted
c) They exclude decomposers
d) Both a and b
Answer: d) Both a and b
Explanation:
Don’t reflect actual energy transfer.
Q23.
In terms of biomass pyramid, forest ecosystems differ from ponds because:
a) Forest biomass pyramid is upright, pond biomass pyramid can be inverted
b) Forest pyramid is inverted, pond is upright
c) Both show inverted biomass
d) Both show upright biomass
Answer: a) Forest biomass pyramid is upright, pond biomass pyramid can be inverted
Explanation:
Due to producers’ biomass differences.
Q24.
Which of the following correctly matches ecosystem with pyramid type?
a) Grassland – Inverted biomass pyramid
b) Ocean – Inverted biomass pyramid
c) Forest – Inverted biomass pyramid
d) Pond – Upright biomass pyramid
Answer: b) Ocean – Inverted biomass pyramid
Explanation:
Oceans show inverted biomass pyramids.
Q25.
Which ecological pyramid gives the most accurate representation of ecosystem function?
a) Pyramid of number
b) Pyramid of biomass
c) Pyramid of energy
d) All are equal
Answer: c) Pyramid of energy
Explanation:
Energy pyramids always upright and reflect true energy flow.
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