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Question #46162
The Question
A zoologist is analyzing the phylogenetic placement of three exclusively marine taxa: Balanoglossus, Ascidia, and Branchiostoma. Which of the following statements is INCORRECT regarding their anatomical and evolutionary relationships?
Options
- A.
Balanoglossus was historically grouped with chordates, but its 'notochord' is actually a stomochord, which is a buccal diverticulum lacking a mesodermal origin.
- B.
Ascidia exhibits retrogressive metamorphosis, meaning the mesodermally derived notochord present in its larval tail is completely lost in the adult stage.
- C.
Branchiostoma represents a primitive chordate where the notochord extends from head to tail and persists throughout life, alongside a ventral solid nerve cord.
- D.
While Ascidia and Branchiostoma are grouped under Protochordata, only Branchiostoma retains the complete fundamental chordate trio in its adult form.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Notochord|Pharyngeal_gill_slits|Dorsal_hollow_nerve_cord|Hemichordata
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often focus so heavily on the complex notochord variations (larval tail vs. head-to-tail persistence vs. stomochord) that their attention is diverted from the other fundamental chordate characters.
The trap exploits this 'attentional blindness' by perfectly describing the Cephalochordate notochord but subtly swapping the chordate 'dorsal hollow nerve cord' with the non-chordate 'ventral solid nerve cord'.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Chordata Fundamental Trio |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |