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Question #46874
The Question
Pheretima possesses a closed circulatory system where blood is circulated by the rhythmic contraction of specific pulsatile structures. If a severe homeostatic imbalance causes a drastic depletion of Ca2+ ions in the earthworm's tissues, which of the following represents the most accurate and immediate consequence on its cardiovascular dynamics?
Options
- A.
The blood glands in segments 4, 5, and 6 will immediately cease the production of phagocytic blood cells and plasma-dissolved haemoglobin.
- B.
The muscular walls of the lateral and lateral oesophageal hearts will fail to contract due to the absence of Ca2+-mediated exposure of myosin-binding sites.
- C.
The valves within the dorsal blood vessel will actively lock in an open position, leading to the pooling of blood in the posterior segments.
- D.
The diffusion of gases across the moist body wall will stop because Ca2+ is a required cofactor for the binding of O2 to haemoglobin in the plasma.
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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
Earthworm Circulatory Closed System|Calcium Homeostasis|Chemical Coordination
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question forces the integration of invertebrate structural anatomy (earthworm circulatory system) with universal physiological principles (Ca2+ dependent muscle contraction).
Students often compartmentalize NCERT chapters, memorizing earthworm heart segments (7, 9, 12, 13) without applying the mechanism of muscle contraction (Chapter 20) to non-human muscular structures.
The trap lies in confusing the unique features of earthworm blood (plasma-dissolved haemoglobin) with the universal requirement of Ca2+ for muscular pumping.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Structural Organisation in Animals - Class 11 |
| Concept | Earthworm Circulatory Closed System |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |