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Q9:
“All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.
Solution :
Theoretical Foundation: Phylum Chordata
The Phylum Chordata is defined by the presence of four diagnostic characters at some stage of their life cycle:
- A dorsal, hollow, single nerve cord.
- A notochord (a flexible, rod-like structure).
- Pharyngeal gill slits.
- A post-anal tail.
Step 1: Analyzing the Taxonomic Hierarchy
To justify the statement, we must differentiate between the subphyla of Chordata. The phylum is divided into three subphyla:
| Subphylum | Notochord Status |
|---|---|
| Urochordata (Tunicates) | Present only in larval tail. |
| Cephalochordata (Lancelets) | Extends from head to tail region, persists throughout life. |
| Vertebrata | Replaced by a vertebral column in adults. |
Step 2: Justifying "All Vertebrates are Chordates"
All members of the subphylum Vertebrata possess the diagnostic features of chordates during their embryonic development. Specifically, they possess a notochord during the embryonic stage [Developmental Biology Axiom]. Since they satisfy all the defining criteria of the phylum Chordata, they are biologically categorized as a subset of the phylum.
Step 3: Justifying "All Chordates are not Vertebrates"
The subphyla Urochordata and Cephalochordata are collectively termed Protochordates. These organisms exhibit the chordate characteristics but lack a true bony or cartilaginous vertebral column (the defining characteristic of subphylum Vertebrata). Since these organisms are chordates but do not possess vertebrae, the second part of the statement is held as true.
Step 4: Logical Synthesis
The relationship can be expressed via set theory where:
Let $C$ be the set of all Chordates and $V$ be the set of all Vertebrates.
$V \subset C$ (Vertebrates are a proper subset of Chordates).
Therefore, every element $x \in V$ must also satisfy $x \in C$, but there exist elements $y$ such that $y \in C$ and $y \notin V$.
Final Solution: The statement is justified because all vertebrates possess a notochord during embryonic development, qualifying them as chordates. However, chordates such as Urochordates and Cephalochordates are excluded from the subphylum Vertebrata because they lack a developed vertebral column, proving that chordate status is a broader taxonomic category than vertebrate status.
More Questions from Class 11 Biology Animal Kingdom EXERCISES
- Q1: What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?
- Q2: If you are given a specimen, what are the steps that you would follow to classify it?
- Q3: How useful is the study of the nature of body cavity and coelom in the classification of animals?
- Q4: Distinguish between intracellular and extracellular digestion?
- Q5: What is the difference between direct and indirect development?
- Q6: What are the peculiar features that you find in parasitic platyhelminthes?
- Q7: What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?
- Q8: Water vascular system is the characteristic of which group of the following:
- Q10: How important is the presence of air bladder in Pisces?
- Q11: What are the modifications that are observed in birds that help them fly?
- Q12: Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?
- Q13: Segmentation in the body is first observed in which of the following:
- Q14: Match the following: (a) Operculum (i) Ctenophora (b) Parapodia (ii) Mollusca (c) Scales (iii) Porifera (d) Comb plates (iv) Reptilia (e) Radula (v) Annelida (f) Hairs (vi) Cyclostomata and Chondrichthyes (g) Choanocytes (vii) Mammalia (h) Gill slits (viii) Osteichthyes
- Q15: Prepare a list of some animals that are found parasitic on human beings.
CBSE Solutions for Class 11 Biology Animal Kingdom
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Plant Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Cell – The Unit of Life
- Biomolecules
- Cell Cycle and Division
- Transport in Plants
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Plant Growth and Development
- Digestion and Absorption
- Breathing and Exchange of Gases
- Body Fluids and Circulation
- Excretory Products and Elimination
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
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