Q.142 Zoology ⭐ 360° Option Elimination Active

NEET 2025 Zoology Question 142 Solution

Topic: Animal Kingdom · Official NTA Booklet Code 45

Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): All vertebrates are chordates but all chordates are not vertebrate. Reason (R): The members of subphylum vertebrata possess notochord during the embryonic period, the notochord is replaced by a cartilaginous or bony vertebral column in adults. In the light of the above statements, choose the correct answer from the options given below:

(1)Both A and R are true and R is the correct explanation of A
(2)Both A and R are true but R is not the correct explanation of A
(3)A is true but R is false
(4)A is false but R is true

✓

Verified Against NTA Final Answer Key

Option (1) : Both A and R are true and R is the correct explanation of A

📚 Animal Kingdom Easy

📋 Given Parameters & Problem Setup

Assertion (A) All vertebrates are chordates but all chordates are not vertebrate.

Reason (R) Members of subphylum vertebrata possess notochord during embryonic period; notochord is replaced by cartilaginous or bony vertebral column in adults.

⚡

The 30-Second Exam Hall Shortcut: ⚡ Chordata vs Vertebrata Axiom Fingerprint

⏱️ Save ~25 seconds

All vertebrates are chordates (possess notochord in embryo), but protochordates keep or lose notochord without forming a backbone -> not all chordates are vertebrates! Reason R explains this fundamental phylogenetic truth verbatim! Both true & R explains A!

1 Analyze Assertion (A):

2 - "All vertebrates are chordates but all chordates are not vertebrates." -> A foundational axiom of zoology! Assertion A is TRUE.

3 Analyze Reason (R):

4 - "The members of subphylum Vertebrata possess notochord during the embryonic period. The notochord is replaced by a cartilaginous or bony vertebral column in the adult." -> NCERT Section 4.2.11 verbatim! Reason R is TRUE.

5 Check explanation link:

6 - Why are protochordates (Urochordates and Cephalochordates) chordates but NOT vertebrates? Because their notochord is NEVER replaced by a vertebral column! Vertebrates alone replace notochord with a vertebral column.

7 Conclusion: Both A and R are true and R is the correct explanation of A.

8 Select Option (1)!

🛡️

Why You Can 100% Trust This Shortcut: Mammalian vs Reptilian Cranial and Heart Morphology (NCERT Biology · Animal Kingdom: Four-chambered heart and homoiothermy).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Phylogenetic Classification of Phylum Chordata

Phylum Chordata is defined by three diagnostic morphological features present at some stage of life: a dorsal hollow nerve cord, a notochord, and paired pharyngeal gill slits:

• Phylum Chordata is divided into three subphyla: Urochordata (Tunicata), Cephalochordata, and Vertebrata.
• Urochordata and Cephalochordata are collectively called protochordates (invertebrate chordates). In Urochordata, notochord is present only in the larval tail; in Cephalochordata, notochord extends from head to tail and persists throughout life.
• In protochordates, a vertebral column is never formed. Hence, they are chordates, but NOT vertebrates.

Step 2

Hallmark of Subphylum Vertebrata

Vertebrates represent a derived clade within Chordata:

• Members of subphylum Vertebrata possess a notochord during the embryonic period.
• In adults, this embryonic notochord is replaced by a protective cartilaginous or bony vertebral column (backbone).
• Because all vertebrates inherit the ancestral chordate traits in the embryo, all vertebrates are chordates.
• Because protochordates lack a vertebral column, all chordates are not vertebrates.

Step 3

Conclusion

Both statements are true and Reason (R) provides the definitive structural and evolutionary explanation for Assertion (A).

\text{Chordates} = \text{Protochordates (no backbone)} + \text{Vertebrates (backbone)}

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. Verifies both statements and recognizes that the vertebral replacement of notochord is the precise defining distinction.

💡

Why this is airtight: None; flawless understanding of chordate taxonomy.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Reason R is the exact, canonical explanation for why the assertion holds true.

⚠️

Student Fallacy (Why candidates pick this trap): Failing to link the definition of vertebrata to chordate inclusion.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Reason R is a literal quote from NCERT.

⚠️

Student Fallacy (Why candidates pick this trap): Doubting embryonic notochord existence in vertebrates.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Assertion A is the most famous axiom in animal classification.

⚠️

Student Fallacy (Why candidates pick this trap): Believing all chordates have a vertebral column.

⚠️

NTA Trap Alert: Reversing the Axiom

Examiners often trick students by writing "All chordates are vertebrates, but all vertebrates are not chordates". Remember: Chordata is the LARGE umbrella phylum; Vertebrata is the SUBPHYLUM inside it!

🛡️ How to avoid the -1 mark: Think: All roses are flowers, but not all flowers are roses. All vertebrates are chordates!

📖

Core NEET Syllabus Standard

NEET Biology Core Syllabus · Animal Kingdom Standard Benchmark

Core Scientific Principle Tested:

"All vertebrates are chordates because they possess an embryonic notochord that is replaced by a vertebral column; protochordates lack this vertebral column."

Syllabus Focus: Phylum Chordata · Subphylum Vertebrata

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Notochord in youth, Backbone in truth -> All Verts are Chordates, but Chordates are broader!

Ready to attempt under real exam pressure?

Test your speed and accuracy in the authentic 180-minute timed NTA simulator.

Launch NEET 2025 CBT Test →

← Previous (Q.141) All Zoology Questions Grid Next (Q.143) →

Spotted a mistake in this solution? Report an error ([email protected])

⚖️ Legal & Fair Dealing Notice: Sourced from publicly released NEET 2025 question papers and NEET answer keys for private study, research, and non-commercial educational practice under Fair Dealing (Section 52(1)(a) of the Indian Copyright Act, 1957). Not affiliated with or endorsed by NTA or NMC.

NEET 2025 Zoology Question 142 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Chordata vs Vertebrata Axiom Fingerprint

Step-by-Step Rigorous Workflow & Mathematical Proof

Phylogenetic Classification of Phylum Chordata

Hallmark of Subphylum Vertebrata

Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: Reversing the Axiom

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Animal Kingdom

Basis of Classification - Body Symmetry in Echinodermata

Class Reptilia - Locomotion and Heart Chamber Exceptions

Fundamental Diagnostic Characteristics of Phylum Chordata

Scientific and Common Names of Chondrichthyes and Osteichthyes

Solve 4 NEET Questions a Day — One per Subject