Q5. Which is not a stem modification: (a) the pitcher of Nepenthes; (b) the thorns of Citrus; (c) the tendrils of cucumber; (d) the flattened stem of Opuntia?
(a): the pitcher is a modified leaf; the others are modified stems (beyond the 2026–27 NCERT text).
Q6. What do the bladders of bladderwort trap, and what are they made from?
Tiny water animals; the bladders are parts of its finely divided leaves (beyond the 2026–27 NCERT text; NCERT page 19 names bladderwort as insectivorous).
Q7. Is a pitcher of Nepenthes a stem or a leaf modification, and how is it attached?
It is a leaf modification: the pitcher and its lid develop in the distal leaf region, connected by a tendril to the expanded photosynthetic part. Developmental studies of Nepenthes rafflesiana describe a pitcher beginning as a swollen tendril tip (beyond the 2026–27 NCERT text).
Q8. Assertion: insectivorous plants are partially heterotrophic. Reason: they carry out no photosynthesis. Are both true?
The assertion is true (NCERT page 19), but the reason is false: insectivorous plants photosynthesise and also digest trapped insects for nitrogen and other minerals (beyond the NCERT text).
Q9. Match each with its modification: pea, onion, cactus.
Pea: leaf tendrils; onion: fleshy storage leaves; cactus: spines (beyond the 2026–27 NCERT text).
Q10. Pea and cucumber tendrils both help the plant climb. Are they homologous or analogous?
Analogous: they do the same job but have different origins, leaflets in pea and stems in cucumber. NCERT Class 12 Biology (Evolution, page 115) describes analogy as “different structures evolving for the same function”; the pea and cucumber example is beyond the NCERT text.
Q11. Where does every leaf, modified or not, arise on the stem?
At a node; a leaf bears a bud in its axil (NCERT page 59).
Q12. Why are the leaves of a cactus reduced to spines while its stem is green?
The spines protect the plant and, with almost no leaf surface, the plant loses less water by transpiration; the green stem takes over photosynthesis (beyond the 2026–27 NCERT text).