MPSC 2024 Prelims Paper-I · Question 58 of 100

Correct — option (1), Bryophyta. The nickname is an analogy with the amphibians of the animal kingdom, which live on land but must return to water to breed, and it fits the bryophytes — the mosses, liverworts and hornworts — for exactly the same reason. They are land plants: they grow on soil, rock, bark and walls, out of the water, and they are among the first colonisers of bare surfaces. But their sexual reproduction is still tied to water, because the male gametes they produce are flagellated antherozoids that must actually swim to reach the egg in the archegonium, and they can only do that through a continuous film of water — a film supplied by rain, dew or the moisture of a shaded damp place. Without it fertilisation cannot occur at all, so a bryophyte can survive in a dry spell but cannot complete its life cycle in one. Two further features reinforce the halfway position. They have no true vascular tissue, no xylem to conduct water upward under tension and no phloem to distribute food, so water moves largely by capillarity over and between the surfaces of the plant and the whole body must stay small and close to the ground. And they have no true roots, stems or leaves in the anatomical sense, being anchored instead by thread-like rhizoids. Their dominant, green, independent phase is the gametophyte, on which the spore-producing sporophyte remains attached and nutritionally dependent — the reverse of the arrangement in every group above them. Land habit with aquatic reproduction is precisely the amphibian condition.

• (2)Pteridophyta — Pteridophytes — the ferns and their allies — also require water for fertilisation, since their antherozoids swim in the same way, and that shared dependence makes this the most defensible of the three wrong choices. What separates them is everything else. Pteridophytes possess true vascular tissue, xylem and phloem, and true roots, stems and leaves, which is why they can stand tall and were the dominant vegetation of the Carboniferous forests; and in them the sporophyte is the large independent plant while the gametophyte is reduced to a small separate prothallus. They are conventionally described as the first true vascular land plants, and the amphibian label belongs to the group that lacks the vascular tissue as well as the independence from water.
• (3)Gymnosperm — Gymnosperms have broken the dependence on water for reproduction entirely, which is the opposite of the amphibian condition. Their male gametes reach the ovule inside a pollen grain carried by wind rather than by swimming, and the pollen tube delivers the gamete directly, so fertilisation can take place in a dry environment and even in the freezing conditions where conifers dominate. They are fully vascular, they are woody perennials, and they bear naked seeds — seeds not enclosed in a fruit, which is what the name records. Pines, cycads and the ginkgo belong here.
• (4)Angiosperm — Angiosperms are the flowering plants and are the most fully terrestrial group of all, so the analogy fits them least. Their seeds are enclosed within a fruit developed from the ovary, they reproduce through pollen carried by wind, water surfaces, insects, birds or bats, and their double fertilisation produces both an embryo and a nutritive endosperm. They possess the most efficient conducting tissue of any plant group, with vessels in the xylem and sieve tubes with companion cells in the phloem, which is part of why they dominate almost every terrestrial habitat on earth today.

The plant kingdom is arranged as a sequence of steps away from water, and each division marks a further degree of independence from it. Algae are aquatic throughout. Bryophytes make the move onto land but keep an aquatic requirement in reproduction, having neither vascular tissue nor true roots, stems and leaves; their green plant body is the haploid gametophyte, and the diploid sporophyte grows attached to it and depends on it. Pteridophytes add vascular tissue and true organs and reverse the alternation of generations so that the sporophyte becomes the dominant plant, but their flagellated antherozoids still need water to swim in. Gymnosperms remove that last requirement by transferring the male gamete inside a pollen grain and delivering it through a pollen tube, and they protect the embryo in a seed, though the seed is not enclosed in a fruit. Angiosperms enclose the seed in a fruit, add the flower as an apparatus for attracting animal pollinators, and evolve the most efficient conducting tissue, which together account for their dominance of terrestrial vegetation. Reading the sequence as a story of escaping water makes every group's defining feature follow from its position in it, and locates the bryophytes as the amphibious stage.

MPSC's biology questions favour nicknames, first-and-only distinctions and defining characters, because each can be tested in a single line: amphibians of the plant kingdom, the first true land plants, naked-seeded plants, vascular cryptogams. Such labels are only useful if the reason behind each is remembered as well as the label itself, since the Commission's distractors are chosen from adjacent groups that share part of the reason — here, pteridophytes, which share the water requirement but not the absence of vascular tissue. The reliable method is to fix the sequence of plant divisions in order and to attach to each the single feature that distinguishes it from the one before, so that any nickname can be reconstructed rather than merely recalled. The same sequence answers questions on alternation of generations, on which group is haploid-dominant, and on where the seed and the fruit first appear.

• Bryophytes are called the amphibians of the plant kingdom because they live on land but require a film of water for fertilisation, their flagellated antherozoids having to swim to the egg in the archegonium.
• They lack true vascular tissue and true roots, stems and leaves, being anchored by rhizoids, which restricts them to small size and to moist, shaded habitats.
• In bryophytes the gametophyte is the dominant, green and independent phase, while the sporophyte remains attached to it and dependent on it — the reverse of the arrangement in pteridophytes and all higher groups.
• Pteridophytes are the first plants with true vascular tissue and true roots, stems and leaves, and their sporophyte is the dominant phase, although they too need water for fertilisation.
• Gymnosperms bear naked seeds and use wind-carried pollen, so they are independent of water for fertilisation, and angiosperms enclose the seed within a fruit and add the flower for animal pollination.

• Choosing pteridophytes because they also need water for fertilisation, when the amphibian label belongs to the group that additionally lacks vascular tissue and true organs
• Assuming a land plant must be independent of water, when the bryophyte life cycle cannot be completed without a film of it
• Forgetting that the dominant phase in bryophytes is the gametophyte, which is the reverse of every group above them
• Confusing the naked seed of gymnosperms with the absence of a seed, when the distinction is whether the seed is enclosed in a fruit

Plant classification appears in MPSC papers as nickname or defining-character recall — the amphibians of the plant kingdom, vascular cryptogams, naked-seeded plants — and as short comparison items asking which group first shows a particular feature. The distractors are drawn from the divisions immediately adjacent in the sequence, so a candidate who has learned the divisions as an ordered series with one distinguishing feature each can answer without memorising the nicknames separately. Expect companion questions on alternation of generations, on the economic uses of Sphagnum, and on where in the sequence the seed, the fruit and the flower first appear.

No directly related past PYQ was found.

• practice — not a real PYQ

  In bryophytes, which of the following is the dominant phase of the life cycle ?

  • (a)The haploid gametophyte
  • (b)The diploid sporophyte
  • (c)The zygote
  • (d)The prothallus

  Answer(a) The haploid gametophyte — the green plant body of a moss or liverwort is the gametophyte, and the spore-producing sporophyte grows attached to it and remains dependent on it for nutrition. In pteridophytes and all higher plants this is reversed, the sporophyte becoming the dominant independent plant; the prothallus is the reduced gametophyte of a fern.

• practice — not a real PYQ

  Which of the following plant groups was the first to develop true vascular tissue along with true roots, stems and leaves ?

  • (a)Algae
  • (b)Bryophyta
  • (c)Pteridophyta
  • (d)Gymnosperms

  Answer(c) Pteridophyta — the ferns and their allies are the first plants with xylem and phloem and with true roots, stems and leaves, which is why they are called vascular cryptogams and why they could grow to tree size in the Carboniferous forests. They still require water for fertilisation, a dependence that gymnosperms finally broke by using wind-carried pollen.