Amongst pea tendrils, opuntia spines, lemon thorns and cucurbit tendril, which ones are homologous structures ?
Give reason. Ans10. Pea tendrils are homologous to Opuntia spines because both are modifications of leaves; lemon thorns are homologous to Cucurbit tendril because both are modified stems. Q.11 Describe one example of artificial selection. Ans11. Cabbage, cauliflower and kohlrabi are derrived from a comman ancestor, colewort by artificial selection. Q.12 Mention two differences in the vascular bundles of Sunflower and Maize stems Ans12. Sunflower and maize stems are different in that : (1) Sunflower has radially arranged, fewer vascular bundles, whereas maize has randomly distributed numerous vascular bundles. (2) Sunflower has open (with cambium) vascular bundles, whereas maize has closed (without cambium) vascular bundles. Q.13 Give any four examples of human reflexes. Ans13. (1) Salivation on the sight or smell of a tasty food. (2) Constriction of pupils on the illumination with bright light. (3) Blinking of eye lids on the approach of an object close to the eyes. (4) Jerk in the le
