CDS (I) 2020 General Knowledge · Question 16 of 120

Correct — C, Pollination, fertilization, division of zygote, formation of embryo, seedling. The order follows the plant's own logic. Pollen has to reach the stigma first, and that transfer is pollination. A tube then grows from the pollen grain down through the style to the ovule, where the male germ cell fuses with the egg — fertilisation — and the fusion produces the zygote. The zygote divides repeatedly to form an embryo inside the ovule, the ovule hardens into a seed and the ovary ripens into a fruit. Only when the seed germinates under suitable conditions does the embryo grow into a seedling. Nothing can be shuffled: no fertilisation without pollination, no zygote without fertilisation, no embryo without a dividing zygote, and no seedling without an embryo.

• (a)Seedling, formation of embryo, pollination, fertilization, division of zygote — Starts at the end. A seedling is what the sequence produces, so it cannot open it, and the zygote cannot divide after the embryo it forms already exists.
• (b)Formation of embryo, seedling, pollination, fertilization, division of zygote — Puts embryo and seedling before pollination has even happened. It also separates fertilisation from the zygote division that immediately follows it.
• (d)Seedling, formation of embryo, division of zygote, pollination, fertilization — Runs the whole sequence backwards, ending with pollination — the step that has to come first.

Sexual reproduction in a flowering plant runs through a fixed chain. The stamen makes pollen; the pistil holds the ovary with its ovules, each carrying an egg cell. Transfer of pollen from stamen to stigma is pollination, self-pollination within one flower or cross-pollination between flowers, carried by wind, water or animals. Fusion of the male germ cell with the egg is fertilisation and yields a zygote. The zygote divides into an embryo, the ovule becomes a seed and the ovary a fruit, and germination turns the embryo into a seedling.

Sequence items are the cheapest marks in a paper if you hold one anchor and reason outwards. The anchor here is that a seedling is an outcome, so any option beginning with it is out — and that removes options (a) and (d) at a glance. Between the two survivors, one begins with the formation of an embryo, which is impossible before fertilisation. That leaves option (c) without any need to recall the middle steps. It is worth separating pollination from fertilisation firmly in the mind, because they are the pair students most often collapse into one: pollination merely delivers the pollen to the stigma, and the actual fusion of gametes happens later and further in, at the ovule.

• Pollination is the transfer of pollen from the stamen to the stigma; fertilisation is the later fusion of the male germ cell with the egg in the ovule.
• A tube grows out of the pollen grain and travels through the style to reach the ovary.
• After fertilisation the zygote divides several times to form an embryo within the ovule.
• The ovule develops a tough coat and becomes the seed; the ovary ripens into the fruit.
• Germination is the process by which the embryo inside the seed develops into a seedling.

• Treating pollination and fertilisation as the same event.
• Placing seed formation before embryo formation; the embryo forms inside the developing seed.
• Assuming pollination guarantees fertilisation — pollen must still germinate and reach the ovule.

As a correct-sequence item, or as a which-comes-immediately-after question on one named stage.

• practice — not a real PYQ

  In a flowering plant, after fertilisation the ovule and the ovary develop respectively into

  • (a)fruit and seed
  • (b)seed and fruit
  • (c)embryo and seed
  • (d)seed and embryo

  Answer(b) seed and fruit — the ovule hardens into the seed while the ovary ripens around it into the fruit.

• practice — not a real PYQ

  The transfer of pollen grains from the anther of one flower to the stigma of another flower is called

  • (a)self-pollination
  • (b)cross-pollination
  • (c)fertilisation
  • (d)germination

  Answer(b) cross-pollination — transfer within the same flower would be self-pollination, and fertilisation is the later fusion of gametes.