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Question #46064
The Question
An indigenous forest ecosystem experiences a severe invasion by the alien weed Lantana camara. Ecologists observe that while the Gross Primary Productivity (GPP) of the ecosystem remains high, secondary productivity drops to near zero, leading to a collapse of higher trophic levels. Which of the following best explains this 'trophic bottleneck'?
Options
- A.
The weed's biomass is unpalatable to native herbivores due to secondary metabolites, trapping energy at the producer level and severely reducing ecological efficiency.
- B.
High respiratory losses (R) in the invasive weed reduce the Net Primary Productivity (NPP) to zero, leaving no available biomass for primary consumers.
- C.
The invasion induces an inverted pyramid of biomass, where the rapid turnover of the weed fails to support a larger standing crop of herbivores.
- D.
Allelopathic chemicals secreted by the weed biomagnify across trophic levels, causing toxicity and top-down collapse of carnivore populations.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Nile Perch|Lake Victoria|Ecosystem Stability
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume that high Primary Productivity (GPP/NPP) automatically translates to high Secondary Productivity.
This question tests the understanding that 'palatability' and 'assimilation efficiency' are absolute prerequisites for energy transfer between trophic levels.
It also traps students who confuse allelopathy (plant-plant chemical inhibition) with biomagnification (toxin accumulation in food chains).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biodiversity and Conservation - Class 12 |
| Concept | Alien Species Invasion Impacts |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |