Before You Begin
Question #46168
The Question
In Urochordates like Ascidia, the notochord is restricted to the larval tail and is lost during retrogressive metamorphosis. Suppose an environmental endocrine disruptor completely inhibits the hormonal pathways governing this metamorphosis. Which of the following represents the most likely phenotypic and ecological outcome for the affected individuals?
Options
- A.
They will exhibit neoteny, retaining a dorsal hollow nerve cord and notochord, while remaining free-swimming.
- B.
They will undergo progressive metamorphosis, converting the retained notochord into a rudimentary vertebral column.
- C.
They will successfully transition to a sessile adult form but retain the post-anal tail as a vestigial structure.
- D.
They will fail to develop a branchial basket and pharyngeal gill slits, losing their primary chordate characteristics.
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
Urochordata|Abscisic_Acid_Antagonism|Vertebral_Column_Formula
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'Urochordata = retrogressive metamorphosis' without visualizing the functional consequences of its failure.
The pivot is understanding that blocking retrogressive metamorphosis results in the retention of the 'Chordate Fundamental Trio' (neoteny) and prevents the ecological shift from pelagic to sessile.
Furthermore, Option B serves as a taxonomic trap, testing the strict boundary that a retained notochord in a Protochordate does not spontaneously evolve into a vertebral column.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Urochordata vs. Cephalochordata |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |