Q.53 Match List I with List II :
| List I | List II |
|---|---|
| (A) Plesiomorphy | (I) A derived trait in an evolutionary series |
| (B) Symplesiomorphy | (II) Possession of derived traits by a group of taxa |
| (C) Synapomorphy | (III) An ancestral or primitive trait/character |
| (D) Apomorphy | (IV) A group of taxa sharing a primitive trait |
Choose the correct answer from the options given below:
(1) (A)-(I), (B)-(III), (C)-(IV), (D)-(II)
(2) (A)-(III), (B)-(IV), (C)-(II), (D)-(I)
(3) (A)-(IV), (B)-(II), (C)-(I), (D)-(III)
(4) (A)-(II), (B)-(I), (C)-(III), (D)-(IV)
Option (2) is correct: (A)-(III), (B)-(IV), (C)-(II), (D)-(I).
Plesiomorphy, symplesiomorphy, synapomorphy, and apomorphy are key cladistic terms distinguishing ancestral versus derived traits in phylogenetic analysis, crucial for reconstructing evolutionary relationships without relying on shared primitive features alone.
Term Definitions
These concepts from Willi Hennig’s cladistics framework classify character states relative to an evolutionary lineage: plesiomorphy as primitive/ancestral, apomorphy as derived/novel.
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Plesiomorphy (A): Ancestral or primitive trait (III), e.g., five fingers in tetrapods relative to derived states like bird wings.
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Symplesiomorphy (B): Shared primitive trait among taxa (IV), e.g., vertebrae in birds and lizards (doesn’t unite them cladistically).
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Synapomorphy (C): Shared derived trait defining a clade (II), e.g., mammary glands in mammals.
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Apomorphy (D): Any derived trait in a lineage (I), unique (autapomorphy) or shared.
Option Analysis
| Option | Mapping | Correct? | Reason |
|---|---|---|---|
| (1) | A-I, B-III, C-IV, D-II | No | Swaps plesiomorphy (ancestral) with apomorphy (derived); confuses synapomorphy. |
| (2) | A-III, B-IV, C-II, D-I | Yes | Matches standard cladistic definitions precisely. |
| (3) | A-IV, B-II, C-I, D-III | No | Misassigns plesiomorphy as shared group trait; apomorphy as primitive. |
| (4) | A-II, B-I, C-III, D-IV | No | Inverts derived/ancestral; treats apomorphy as shared primitive. |
Plesiomorphy symplesiomorphy synapomorphy apomorphy matching questions test cladistics fundamentals in NEET/GATE Life Sciences, distinguishing ancestral (plesio-) from derived (apo-) traits for accurate phylogenies.
Cladistics Basics
Cladistics builds trees using synapomorphies (shared derived traits) to define monophyletic clades, avoiding symplesiomorphies (shared primitives) that unite unrelated taxa. Example: Feathers are synapomorphy for birds; scales are symplesiomorphy for reptiles + birds vs. mammals.
Matching Breakdown
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Plesiomorphy: Primitive trait (e.g., ectothermy in birds vs. endothermy).
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Symplesiomorphy: Primitive trait shared by non-sister taxa (e.g., lungs in amphibians + mammals).
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Synapomorphy: Derived trait shared by clade (e.g., hair in mammals).
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Apomorphy: Novel trait (e.g., whale fluke as autapomorphy).
Exam Strategy
Memorize: Plesio = primitive (ancestral/shared); Apo = derived (unique/shared). Option (2) aligns perfectly—practice with vertebrate evolution trees.
