How NEET Tests 'Anatomy' - High-Yield Traps
This is a high-yield, diagram-based chapter. The hard questions are almost always discriminators and exceptions, not plain recall. Master these rank-splitters:
- Which cells are living vs dead: LIVING → parenchyma, collenchyma, xylem parenchyma, sieve tube (enucleate but living), companion cell, phloem parenchyma. DEAD → sclerenchyma (fibres + sclereids), tracheids, vessels, xylem fibres, phloem fibres, cork.
- Only-one-of-its-kind facts: xylem parenchyma = the only living xylem cell; phloem fibre = the only dead phloem cell; sieve tube = the only enucleate living cell.
- Angiosperm vs gymnosperm: vessels & companion cells + sieve tubes are angiosperm features; gymnosperm xylem has only tracheids (no vessels) and gymnosperm phloem has albuminous cells (no companion cells) and no sieve tubes.
- Endarch vs exarch: stem xylem = endarch (protoxylem inner); root xylem = exarch (protoxylem outer).
- Radial vs conjoint: root = radial (xylem & phloem alternate); stem/leaf = conjoint collateral.
- Dicot vs monocot discriminators: root - xylem arches (2-4 vs polyarch) & pith (small vs large); stem - bundles in a ring & open vs scattered & closed; bundle sheath & protoxylem lacuna are monocot-stem markers; hypodermis - collenchyma (dicot) vs sclerenchyma (monocot).
- Casparian strips = suberin/lignin bands on the radial/tangential walls of the endodermis; passage cells let water reach the xylem.
- Secondary growth: more secondary xylem than phloem is formed; heartwood is dead & non-conducting (with tyloses) while sapwood conducts; cork is made by phellogen and is suberised; lenticels allow gas exchange; bark = everything outside the vascular cambium.
- Interfascicular cambium & cork cambium arise by dedifferentiation of permanent (parenchyma) cells.
Below are challenging assertion-reason, match-the-column, multi-statement and sequence questions built on exactly these distinctions.