The Question is from neet-zoology animal-kingdom fundamental-characters-of-chordata, and it was created by the author A SUBRAMANYAM

Question

A newly discovered marine organism possesses pharyngeal gill slits, a post-anal tail, a notochord extending beyond the nerve cord, and a dorsal tubular nerve cord. However, it lacks a vertebral column.  This organism is most likely a member of which group?

A SUBRAMANYAM · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Chordate characteristics and classification
 **Related Topics**: Phylogeny of chordates, invertebrate chordates, vertebrate evolution
 **Prerequisites**: Understanding of basic chordate anatomy and the characteristics defining different chordate subphyla.
## SOLUTION PATHWAY
**Given Information**:
  The organism possesses pharyngeal gill slits, a post-anal tail, a notochord (extending beyond the nerve cord), and a dorsal tubular nerve cord.
  The organism lacks a vertebral column.
**Method & Steps**:
 1. Identify the key characteristics present in the organism.
  Reasoning: The presence of pharyngeal gill slits, a post-anal tail, a notochord, and a dorsal, hollow nerve cord are all defining characteristics of chordates.
  Formula/Rule: None directly applicable, this is a classification problem based on observable traits.
 2. Determine which chordate subphyla possess these characteristics but lack a vertebral column.
  Working:  Vertebrates (Vertebrata) are characterized by the presence of a vertebral column, which this organism lacks.  Urochordates (Urochordata) possess these characteristics at some point in their lifecycle, but often lose them in their adult form. Cephalochordates (Cephalochordata) retain all these characteristics throughout their life and lack a vertebral column. Hemichordates (Hemichordata) are deuterostomes, but they don't possess all the defining characteristics of chordates (e.g., a notochord extending the length of the body, a post-anal tail).
  Key Point: The notochord's extension beyond the nerve cord is a key differentiator between cephalochordates and urochordates. While urochordates have a notochord, it's usually restricted to the larval stage.
 3. Conclude the most likely subphylum based on the given information.
  Result: Cephalochordates (lancelets) are the most likely group because they possess all the listed chordate characteristics throughout their life and lack a vertebral column.
  Verification:  Review the defining characteristics of each subphylum to ensure the chosen answer aligns with the observed traits.
 ## OPTION ANALYSIS
[A] :x: Urochordata (tunicates): While tunicates possess these characteristics at some larval stage, they are largely absent in the adult form.  The question describes a mature organism.
[B] ✓: Cephalochordata (lancelets): Lancelets retain all the listed chordate characteristics throughout their lives and lack a vertebral column, perfectly matching the description.
[C] :x: Vertebrata: Vertebrates possess a vertebral column, which the organism lacks.
[D] :x: Hemichordata: Hemichordates are not considered true chordates; they lack some key features like a post-anal tail and a dorsal hollow nerve cord running the length of the body.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the characteristics of different chordate subphyla: Thoroughly understanding the defining characteristics of each group is crucial for accurate classification.
  2.Overlooking the significance of the notochord's extent: The notochord's extension beyond the nerve cord is a key distinguishing feature between cephalochordates and urochordates.
 **Quick Tips**:
  1.Create a table summarizing the key characteristics of each chordate subphylum to facilitate quick comparison.
  2.Remember that the presence or absence of a vertebral column is a crucial factor in distinguishing vertebrates from other chordates.

A SUBRAMANYAM · Answer

Urochordata

A SUBRAMANYAM · Answer

The correct Option is "Cephalochordata"

A SUBRAMANYAM · Answer

Vertebrata

A SUBRAMANYAM · Answer

Hemichordata

NEET Zoology Animal Kingdom Fundamental Characters Of Chordata MCQs

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