(a) Fig. 1.1 shows the longitudinal section of a flower. Fig. 1.1 (i) Name the structures labelled X, Y and Z on Fig. 1.1. [3] (ii) State the function of st...

Labelled answer diagram:

(a)(i) The structures labelled on the longitudinal section of the flower: [3]

• X = Anther (the part of the stamen that produces and releases pollen grains) [1]
• Y = Ovary (the swollen base of the carpel/pistil that contains the ovules) [1]
• Z = Stigma (the sticky receptive surface at the top of the carpel where pollen lands) [1]

(a)(ii) The function of structure Y (the ovary) is to contain the ovules, which, after fertilisation, develop into seeds. [1] The ovary wall itself develops into the fruit wall (pericarp), protecting the developing seeds.

(b) Pollination is the transfer of pollen grains from the anther to the stigma of a flower. [1] It is a physical transport event that can be carried out by wind, insects or other agents. Fertilisation is the fusion of the male gamete (from the pollen grain) with the female gamete (egg cell) inside the ovule. [1] Pollination must occur first to deliver the pollen to the stigma; only then can the pollen tube grow down the style to the ovule and fertilisation can take place. Pollination delivers the pollen; fertilisation is the actual union of the sex cells to form a zygote. [1]

(c) Two features that distinguish wind-pollinated flowers from insect-pollinated flowers (any two paired comparisons): [2]

1. Wind-pollinated flowers have small, inconspicuous petals (or no petals at all), since they do not need to attract insects; insect-pollinated flowers have large, brightly coloured petals to attract pollinators. [1]
2. Wind-pollinated flowers produce large quantities of light, smooth pollen that is easily carried by air currents; insect-pollinated flowers produce smaller amounts of sticky or spiny pollen that adheres to the body of visiting insects. [1]

Another acceptable comparison: wind-pollinated flowers have large, feathery stigmas that hang outside the flower to catch airborne pollen, while insect-pollinated flowers have stigmas positioned inside the flower where visiting insects will brush against them.