Question

Which one of the following statements is FALSE?

• A. More than 80% of the solar energy incident on earth is captured by plants and photosynthetic bacteria.
• B. Only 10% of energy is transferred to each of the higher trophic levels in grazing food chain.
• C. All organisms of a trophic level should be included for estimation of energy content of that trophic level.
• D. The movement of energy is unidirectional in the ecological pyramid of energy.

Hint:

Plants are actually very inefficient at harvesting overall solar energy.
They capture only $2\text{--}10\%$ of the Photosynthetically Active Radiation (PAR), which is a tiny fraction of the total sunlight hitting the Earth.

Answer 1

The Correct Option is A

Step 1 : Understanding the Question:
The question asks to identify which of the given ecological statements is false.

Step 2 : Key Formulas and Approach:
The approach involves reviewing thermodynamic and ecological principles governing energy capture and flow through trophic levels in an ecosystem.

Step 3 : Detailed Explanation:

• Solar Energy Capture: Out of the total solar radiation incident on Earth, less than $50\%$ represents Photosynthetically Active Radiation (PAR).
Plants and photosynthetic bacteria capture only $2\text{--}10\%$ of this PAR.
This means they capture only about $1\text{--}5\%$ of the total incident solar energy, not "more than $80\%$". Thus, statement (A) is completely false.

• Ten Percent Law: According to Lindeman's $10\%$ law of trophic efficiency, only about $10\%$ of the energy in one trophic level is transferred to the next higher level, while the rest is lost as heat or used in respiration. Thus, statement (B) is correct.

• Trophic Level Estimation: To accurately calculate the total biomass, energy, or numbers of a trophic level, all organisms belonging to that level must be accounted for. Thus, statement (C) is correct.

• Unidirectional Flow: Energy flow in an ecosystem is strictly unidirectional, moving from primary producers to herbivores and then to carnivores. It can never flow backwards. Thus, statement (D) is correct.

Step 4 : Final Answer:
Therefore, the false statement is Option (A).