NCERT Solutions for Class 11 Biology Chapter 3: Plant Kingdom (NCERT 2026–27)

These Class 11 Biology Chapter 3 solutions cover Plant Kingdom from the NCERT Biology textbook (session 2026–27). The chapter classifies Kingdom Plantae into algae, bryophytes, pteridophytes, gymnosperms and angiosperms, tracing how each group reproduces and how life cycles shift from a dominant gametophyte to a dominant sporophyte. Below you get every NCERT “Exercises” question reproduced verbatim and solved in clear, exam-ready prose, plus extra questions, MCQs, Assertion–Reason items and FAQs.

Class: 11 Subject: Biology Chapter: 3 Title: Plant Kingdom Exercises: 11 questions Session: 2026–27
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Class 11 Biology Chapter 3 Solutions – Overview

Chapter 3, Plant Kingdom, classifies Kingdom Plantae after the broad Five Kingdom system of Whittaker (1969). With cyanobacteria, fungi and the wall-bearing Monera/Protista now excluded, Plantae is studied as five groups: Algae (chlorophyll-bearing, thalloid, mostly aquatic autotrophs, divided into Chlorophyceae, Phaeophyceae and Rhodophyceae); Bryophytes (the “amphibians of the plant kingdom,” with a dominant gametophyte and a dependent sporophyte); Pteridophytes (the first vascular land plants, with a dominant sporophyte and a free-living prothallus); Gymnosperms (naked-seeded, heterosporous plants with cones); and Angiosperms (flowering plants with seeds enclosed in fruits, split into dicots and monocots). The chapter also outlines how classification systems evolved from artificial to natural to phylogenetic, supported by numerical taxonomy, cytotaxonomy and chemotaxonomy.

Key Concepts & Definitions

Thallus: a plant body not differentiated into true root, stem and leaves (as in algae and many bryophytes).

Isogamy / Anisogamy / Oogamy: sexual reproduction by fusion of gametes that are morphologically similar (isogamy), dissimilar in size (anisogamy), or a large non-motile egg with a small motile male gamete (oogamy).

Gametophyte & Sporophyte: the haploid (n), gamete-producing phase and the diploid (2n), spore-producing phase of a plant’s life cycle. Spores are produced after meiosis (reduction division).

Antheridium & Archegonium: the multicellular male sex organ producing antherozoids, and the flask-shaped female sex organ producing a single egg.

Homospory & Heterospory: production of one kind of spore (homospory) versus two kinds — large megaspores and small microspores (heterospory), as in Selaginella and Salvinia.

Gymnosperm vs Angiosperm: gymnosperms bear naked, exposed ovules/seeds; angiosperms enclose ovules in an ovary and seeds in fruits.

NCERT Exercises — Full Solutions

All questions below are reproduced verbatim from the NCERT “Exercises” section of Chapter 3, Plant Kingdom. Answers are original and written in CBSE exam-ready style.

1. What is the basis of classification of algae?

ANSWER Algae are classified into three classes mainly on the basis of three features: (i) the type of photosynthetic pigments present, (ii) the form of stored (reserve) food, and (iii) the chemical composition of the cell wall, along with the number and position of flagella. On this basis the three classes are: Chlorophyceae (green algae) — chlorophyll a and b, food stored as starch, cellulose wall; Phaeophyceae (brown algae) — chlorophyll a and c with fucoxanthin, food as mannitol/laminarin, wall of cellulose and algin; and Rhodophyceae (red algae) — chlorophyll a and d with r-phycoerythrin, food as floridean starch.

2. When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?

ANSWER Reduction division (meiosis) always converts the diploid sporophytic tissue into haploid spores or, in seed plants, into the spores that begin the gametophyte.
PlantWhen & where meiosis occurs
Liverwort (e.g. Marchantia)In the capsule of the sporophyte, where spore mother cells divide to form haploid spores.
Moss (e.g. Funaria)In the capsule of the sporophyte, producing haploid spores.
Fern (pteridophyte)In the sporangia borne on the sporophyll, where spore mother cells undergo meiosis to form spores.
GymnospermIn the microsporangia (forming microspores/pollen) and in the megasporangium/nucellus of the ovule (megaspore mother cell forming megaspores).
AngiospermIn the anther (microsporangia) forming microspores/pollen, and in the ovule (nucellus) where the megaspore mother cell forms megaspores.

3. Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.

ANSWER Three groups of plants that bear archegonia are bryophytes, pteridophytes and gymnosperms. Life cycle of a moss (bryophyte): The dominant phase is the haploid gametophyte. A spore germinates into a creeping, filamentous protonema, which buds to form the leafy gametophore bearing the sex organs — antheridia (producing biflagellate antherozoids) and archegonia (each producing a single egg). Water carries an antherozoid to the egg, and fertilisation forms a diploid zygote. The zygote does not undergo meiosis at once; it develops into a sporophyte (foot, seta and capsule) that stays attached to and dependent on the gametophyte. Inside the capsule, spore mother cells undergo meiosis to form haploid spores, which germinate to start the cycle again. The cycle thus shows a clear alternation of generations with a dominant gametophyte.

4. Mention the ploidy of the following: protonemal cell of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a fern; gemma cell in Marchantia; meristem cell of monocot, ovum of a liverwort, and zygote of a fern.

ANSWER
StructurePloidy
Protonemal cell of a mossHaploid (n)
Primary endosperm nucleus in a dicotTriploid (3n)
Leaf cell of a mossHaploid (n)
Prothallus cell of a fernHaploid (n)
Gemma cell in MarchantiaHaploid (n)
Meristem cell of a monocotDiploid (2n)
Ovum of a liverwortHaploid (n)
Zygote of a fernDiploid (2n)

5. Write a note on economic importance of algae and gymnosperms.

ANSWER Economic importance of algae: Algae carry out at least half of the total carbon-dioxide fixation on Earth and raise dissolved oxygen, acting as primary producers at the base of aquatic food chains. About 70 species are used as food (e.g. Porphyra, Laminaria, Sargassum). They yield hydrocolloids such as algin (brown algae) and carrageenan (red algae). Agar from Gelidium and Gracilaria is used to culture microbes and in ice-creams and jellies. Chlorella, rich in protein, is used as a food supplement, even by space travellers. Economic importance of gymnosperms: Conifers supply softwood timber for construction, furniture and plywood, and are a major source of paper pulp. They yield resin and turpentine (from Pinus). Cycas and Pinus seeds are edible, Ephedra gives the drug ephedrine used in respiratory ailments, and species such as Pinus, Cedrus and Ginkgo are grown as ornamentals.

6. Both gymnosperms and angiosperms bear seeds, then why are they classified separately?

ANSWER Although both produce seeds, the key difference lies in how the ovules and seeds are protected. In gymnosperms the ovules are not enclosed by an ovary wall; they remain exposed both before and after fertilisation, so the resulting seeds are naked. There are no true flowers or fruits, the reproductive structures being cones. In angiosperms the ovules are enclosed within an ovary that is part of a flower; after fertilisation the ovary ripens into a fruit and the seeds lie enclosed inside the fruit. Angiosperms also show double fertilisation and form endosperm. Because of these fundamental differences in seed protection, flowering and fruit formation, the two groups are classified separately.

7. What is heterospory? Briefly comment on its significance. Give two examples.

ANSWER Heterospory is the production of two different kinds of spores by a plant — large megaspores and small microspores — in contrast to homospory, where all spores are alike. Significance: The megaspores develop into female gametophytes and the microspores into male gametophytes. The female gametophyte (and developing embryo) is retained on the parent sporophyte, providing protection and nourishment. This retention and the resulting embryo development on the parent is regarded as a precursor to the seed habit, a major evolutionary advance. Examples: Selaginella and Salvinia.

8. Explain briefly the following terms with suitable examples:-(i) protonema (ii) antheridium (iii) archegonium (iv) diplontic (v) sporophyll (vi) isogamy

ANSWER (i) Protonema: the first, creeping, green, branched, filamentous stage of a moss gametophyte that develops directly from a germinating spore and later forms the leafy shoot. Example: Funaria. (ii) Antheridium: the multicellular male sex organ of bryophytes and pteridophytes that produces motile male gametes (antherozoids). Example: antheridium of a moss/fern. (iii) Archegonium: the multicellular, flask-shaped female sex organ that produces a single egg, found in bryophytes, pteridophytes and gymnosperms. Example: archegonium of Marchantia. (iv) Diplontic: a life cycle in which the diploid sporophyte is the dominant, photosynthetic phase and the gametophyte is highly reduced. Example: angiosperms (and seed plants in general). (v) Sporophyll: a leaf-like appendage that bears sporangia. Example: microsporophylls and megasporophylls of gymnosperms; sporophylls in Selaginella. (vi) Isogamy: sexual reproduction by the fusion of two morphologically similar gametes (similar in size and form). Example: Ulothrix, Spirogyra.

9. Differentiate between the following:-(i) red algae and brown algae (ii) liverworts and moss (iii) homosporous and heterosporous pteridophyte

ANSWER (i) Red algae vs Brown algae:
Red algae (Rhodophyceae)Brown algae (Phaeophyceae)
Red colour due to r-phycoerythrin.Brown colour due to fucoxanthin.
Pigments: chlorophyll a, d and phycoerythrin.Pigments: chlorophyll a, c and carotenoids/xanthophylls.
Stored food: floridean starch.Stored food: mannitol and laminarin.
Flagella absent on reproductive cells.Motile cells with two unequal, laterally attached flagella.
Examples: Polysiphonia, Porphyra.Examples: Laminaria, Fucus.
(ii) Liverworts vs Moss:
LiverwortsMosses
Plant body thalloid and dorsiventral, closely appressed to substrate.Gametophyte upright with slender axes bearing spirally arranged leaves.
Asexual reproduction by gemmae in gemma cups and by fragmentation.Vegetative reproduction by fragmentation and budding of the secondary protonema.
Sporophyte is simpler (foot, seta, capsule).Sporophyte more elaborate, with an advanced spore-dispersal mechanism.
Example: Marchantia.Example: Funaria, Sphagnum.
(iii) Homosporous vs Heterosporous pteridophyte:
HomosporousHeterosporous
Produce only one kind of spore (all similar).Produce two kinds of spores — megaspores and microspores.
Gametophyte usually bisexual and free-living.Gametophytes unisexual; female gametophyte retained on parent.
No precursor to seed habit.Shows a precursor to the seed habit.
Example: most ferns (Dryopteris, Pteris).Example: Selaginella, Salvinia.

10. Match the following (column I with column II)

ANSWER
Column IColumn II
(a) Chlamydomonas(iii) Algae
(b) Cycas(iv) Gymnosperm
(c) Selaginella(ii) Pteridophyte
(d) Sphagnum(i) Moss
Correct matching: (a)–(iii), (b)–(iv), (c)–(ii), (d)–(i).

11. Describe the important characteristics of gymnosperms.

ANSWER 1. Gymnosperms (gymnos = naked, sperma = seeds) are plants in which the ovules are not enclosed by an ovary wall and remain exposed; the seeds that form after fertilisation are therefore naked. 2. They are medium to tall trees and shrubs; Sequoia (giant redwood) is among the tallest tree species. Roots are generally tap roots, sometimes with mycorrhiza (Pinus) or N2-fixing coralloid roots (Cycas). 3. Leaves may be simple or compound (pinnate in Cycas); in conifers, needle-like leaves with thick cuticle and sunken stomata reduce water loss. 4. They are heterosporous, producing microspores and megaspores in sporangia borne on sporophylls arranged into compact strobili/cones (male and female). 5. The male and female gametophytes are highly reduced and are not free-living — they stay within the sporangia on the sporophyte. The male gametophyte is the pollen grain; the female gametophyte bears archegonia. 6. Pollen is carried by air to the ovule; a pollen tube delivers the male gamete to the archegonium. After fertilisation, the zygote develops into an embryo and the ovule into a naked seed.

Extra Practice Questions

Short Answer Type Questions

Q1. Why are bryophytes called the “amphibians of the plant kingdom”?

ANSWERBecause, like amphibians, they can live on land (in soil) but still depend on water for sexual reproduction — the motile antherozoids need a film of water to swim to the archegonium for fertilisation.

Q2. Name the pigments and stored food of Chlorophyceae.

ANSWERChlorophyceae (green algae) contain chlorophyll a and b as the dominant pigments and store food mainly as starch, often around pyrenoids in the chloroplasts.

Q3. What are gemmae and what is their function?

ANSWERGemmae are green, multicellular, asexual buds formed in cup-like structures called gemma cups on the thalli of liverworts. They detach from the parent and germinate into new individuals, serving in vegetative (asexual) reproduction.

Q4. Differentiate between coralloid roots and mycorrhizal roots in gymnosperms.

ANSWERCoralloid roots (in Cycas) are small, specialised roots associated with N2-fixing cyanobacteria. Mycorrhizal roots (in Pinus) show a symbiotic association with fungi that helps in absorbing water and minerals.

Q5. What is meant by phylogenetic classification?

ANSWERIt is a system of classification based on evolutionary relationships among organisms, assuming that members of the same taxon share a common ancestor. It uses many sources of information and is currently the most acceptable system.

Long Answer Type Questions

Q1. Compare the life cycles of a moss and a fern with respect to the dominant phase and the role of water.

ANSWERIn a moss (bryophyte), the dominant, photosynthetic phase is the haploid gametophyte; the diploid sporophyte (foot, seta, capsule) is small and dependent on the gametophyte for nourishment. In a fern (pteridophyte), the dominant phase is the diploid sporophyte with true root, stem, leaves and vascular tissue, while the gametophyte is a small, free-living prothallus. In both, the sex organs are antheridia and archegonia, and water is essential for fertilisation because the motile antherozoids must swim to the egg in the archegonium. Both show alternation of generations, but the trend from moss to fern is a shift towards a more dominant, independent sporophyte — an evolutionary advance suited to life on land.

Q2. Trace the evolutionary trends in the plant kingdom from algae to angiosperms.

ANSWERFrom algae to angiosperms there is a clear progression. Algae are simple aquatic thalloid autotrophs dependent on water. Bryophytes move onto land but remain dependent on water for reproduction, with a dominant gametophyte. Pteridophytes develop true roots, stems, leaves and vascular tissues, with a dominant sporophyte, and some show heterospory — a step towards the seed habit. Gymnosperms achieve the seed habit with naked seeds, pollen tubes (so water is no longer needed for fertilisation) and reduced, dependent gametophytes. Angiosperms are the most advanced: ovules are enclosed in an ovary, seeds are enclosed in fruits, flowers aid pollination, and double fertilisation produces endosperm. The overall trends are: increasing differentiation of the plant body, development of vascular tissue, shift from a dominant gametophyte to a dominant sporophyte, reduction of the gametophyte, freedom from water for fertilisation, and progressive protection of the embryo and seed.

Q3. Explain how classification systems for plants have changed from artificial to natural to phylogenetic.

ANSWERArtificial systems (e.g. Linnaeus) used only a few gross morphological characters such as habit and androecium structure, giving equal weight to vegetative and sexual characters; they often separated closely related species and were easily misled by environmentally affected vegetative traits. Natural systems (e.g. Bentham and Hooker) used natural affinities, considering both external and internal features such as anatomy, embryology and phytochemistry, grouping truly related plants together. Phylogenetic systems, now the most accepted, classify plants on the basis of evolutionary relationships and common ancestry. They are aided by numerical taxonomy (computer analysis of many characters, each given equal weight), cytotaxonomy (chromosome number, structure and behaviour) and chemotaxonomy (chemical constituents), which together resolve difficulties where fossil evidence is lacking.

MCQs & Assertion–Reason

1. The red colour of red algae is due to the pigment:

(a) fucoxanthin    (b) r-phycoerythrin    (c) chlorophyll b    (d) carotene

2. Stored food in brown algae (Phaeophyceae) is mainly:

(a) starch    (b) floridean starch    (c) mannitol and laminarin    (d) glycogen

3. Bryophytes are called amphibians of the plant kingdom because they:

(a) live only in water    (b) need water for sexual reproduction    (c) have true roots    (d) bear flowers

4. The dominant phase in the life cycle of a moss is the:

(a) sporophyte    (b) gametophyte    (c) zygote    (d) seed

5. Pteridophytes are evolutionarily important as the first plants to possess:

(a) flowers    (b) seeds    (c) vascular tissues    (d) fruits

6. Naked seeds are characteristic of:

(a) angiosperms    (b) gymnosperms    (c) bryophytes    (d) algae

7. Coralloid roots associated with N2-fixing cyanobacteria are found in:

(a) Pinus    (b) Cycas    (c) Cedrus    (d) Ginkgo

8. Examples of heterosporous pteridophytes are:

(a) Dryopteris and Pteris    (b) Funaria and Sphagnum    (c) Selaginella and Salvinia    (d) Volvox and Ulothrix

9. The natural system of classification for flowering plants was given by:

(a) Linnaeus    (b) Whittaker    (c) Bentham and Hooker    (d) Engler

10. The ploidy of the primary endosperm nucleus in a dicot is:

(a) haploid (n)    (b) diploid (2n)    (c) triploid (3n)    (d) tetraploid (4n)

Answer key: 1-(b), 2-(c), 3-(b), 4-(b), 5-(c), 6-(b), 7-(b), 8-(c), 9-(c), 10-(c).

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: Cyanobacteria are no longer classified as algae.

Reason: Members of Monera have been excluded from Kingdom Plantae in modern classification.

A-R 2. Assertion: In gymnosperms, water is not needed for fertilisation.

Reason: A pollen tube carries the male gametes to the archegonia in the ovule.

A-R 3. Assertion: The sporophyte of a bryophyte is fully independent.

Reason: The sporophyte produces haploid spores after meiosis in the capsule.

A-R 4. Assertion: Heterospory is regarded as a precursor to the seed habit.

Reason: The female gametophyte and developing embryo are retained on the parent sporophyte.

A-R 5. Assertion: Angiosperm seeds are enclosed within fruits.

Reason: In angiosperms the ovules are enclosed within an ovary that ripens into a fruit.

Answer key: 1-(A), 2-(A), 3-(D), 4-(A), 5-(A).

Common Mistakes & Exam Tips

Common mistakes to avoid

  • Calling cyanobacteria (blue-green algae) “algae” — they are Monera and excluded from Plantae.
  • Confusing the dominant phase: gametophyte dominates in bryophytes, but sporophyte dominates in pteridophytes, gymnosperms and angiosperms.
  • Writing that gymnosperms have fruits or flowers — they have naked seeds and cones, no fruit.
  • Mixing up pigments and stored food of the three algal classes (use the table in Q1/Q9).
  • Forgetting that meiosis occurs in the sporophytic tissue (capsule/sporangium/nucellus), not in the gametophyte.
  • Stating the primary endosperm nucleus is diploid — it is triploid (3n) due to triple fusion.

How to score full marks in this chapter

Memorise the comparison tables (algal classes; liverworts vs mosses; homo- vs heterospory) because they are direct “differentiate” answers. Always give a named example with every term, draw and label the moss/fern life cycle when asked, and state ploidy with both the word and the symbol (e.g. haploid, n). For evolutionary-trend questions, structure the answer as a progression from algae → angiosperms highlighting vascular tissue, the seed habit and the shift in dominant phase.

Frequently Asked Questions

What is Class 11 Biology Chapter 3 Plant Kingdom about?

It classifies Kingdom Plantae into algae, bryophytes, pteridophytes, gymnosperms and angiosperms, describing the structure, reproduction and life cycle of each group and how plant classification systems evolved from artificial to phylogenetic.

How many exercise questions are there in Chapter 3 Plant Kingdom?

The NCERT “Exercises” section has 11 questions, including match-the-following, ploidy, and differentiate-type questions. All 11 are reproduced verbatim and fully solved on this page.

Why are gymnosperms and angiosperms classified separately if both bear seeds?

Gymnosperms bear naked, exposed ovules and seeds with no ovary or fruit, while angiosperms enclose ovules in an ovary and seeds inside fruits, and have flowers and double fertilisation — so they are placed in separate groups.

Are these Class 11 Biology Chapter 3 solutions free?

Yes. All solutions are free and follow the official NCERT Biology textbook for session 2026–27.

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