Plant Kingdom Class 11 Biology: Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms

What Plant Kingdom is about

Weightage: This chapter is part of Unit I, Diversity of Living Organisms, which carries 15 of the 70 theory marks in the school annual exam together with The Living World, Biological Classification and Animal Kingdom.Source: CBSE Biology (044) syllabus 2026-27, Class XI course structure, Unit I Diversity of Living Organisms

Key concepts

Systems of classification: artificial, natural and phylogenetic

NCERT section Introduction (artificial, natural and phylogenetic systems; numerical taxonomy, cytotaxonomy, chemotaxonomy)

Artificial systems (e.g. Linnaeus) used only a few superficial morphological characters such as habit, colour, number and shape of leaves, or the number of stamens and other floral parts. They gave equal weightage to vegetative and sexual characters; this is misleading because vegetative characters are more easily affected by the environment. Closely related species could end up far apart.

Natural systems used natural affinities among organisms: not only external features but also internal ones such as ultra-structure, anatomy, embryology and phytochemistry. Bentham and Hooker's classification of flowering plants is an example.

Phylogenetic systems (present day) are based on evolutionary relationships, assuming organisms of the same taxon have a common ancestor. Fossil evidence is not always available, so other information helps:

• Numerical taxonomy: computers handle all observable characters; each character is given a number and code, and equal importance is given to every character, so hundreds of characters can be considered at once.
• Cytotaxonomy: based on cytological information such as chromosome number, structure and behaviour.
• Chemotaxonomy: uses the chemical constituents of the plant to resolve confusions.

Worked example

Why was Linnaeus's system called artificial? How does numerical taxonomy differ from it? (3 marks)

Try it first, then show the solutionSolution

1. Linnaeus used only a few superficial characters such as the number of stamens, so unrelated plants could be grouped together. (1)
2. It gave equal weightage to vegetative and sexual characters, though vegetative characters are easily changed by the environment. (1)
3. Numerical taxonomy uses all observable characters, codes each as a number and analyses them by computer, giving equal importance to each. (1)

Answer: Few superficial characters made it artificial; numerical taxonomy uses all characters with computers.

Algae: general features and reproduction

NCERT section 3.1 Algae

Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic (fresh water and marine) organisms. They also occur on moist stones, soils and wood, and some live with fungi (lichens) or on animals (on the sloth bear).

Form and size: from colonial forms like *Volvox* and filamentous forms like *Ulothrix* and *Spirogyra*, to massive marine kelps.

Reproduction:

• Vegetative: by fragmentation; each fragment grows into a thallus.
• Asexual: by spores, most commonly zoospores (flagellated, motile), which germinate into new plants.
• Sexual: by fusion of two gametes:
• Isogamous: gametes similar in size; flagellated (*Ulothrix*) or non-flagellated (*Spirogyra*).
• Anisogamous: gametes dissimilar in size (some species of *Chlamydomonas*).
• Oogamous: a large non-motile female gamete fuses with a smaller motile male gamete (*Volvox*, *Fucus*).

Usefulness:

• Algae fix at least half of the total CO₂ on earth by photosynthesis and increase dissolved oxygen around them; they are primary producers at the base of aquatic food chains.
• 70 species of marine algae (e.g. *Porphyra*, *Laminaria*, *Sargassum*) are used as food.
• Some marine brown algae give algin and red algae give carrageen, used commercially.
• Agar from *Gelidium* and *Gracilaria* is used to grow microbes and in ice-creams and jellies.
• *Chlorella*, a protein-rich single-celled alga, is taken as a food supplement; even astronauts have used it.

Worked example

Distinguish isogamy, anisogamy and oogamy with one algal example each. (3 marks)

Try it first, then show the solutionSolution

1. Isogamy: fusing gametes similar in size; e.g. Ulothrix (flagellated) or Spirogyra (non-flagellated). (1)
2. Anisogamy: gametes dissimilar in size; e.g. some species of Chlamydomonas. (1)
3. Oogamy: large non-motile female gamete with small motile male gamete; e.g. Volvox or Fucus. (1)

Answer: Isogamy (Ulothrix, Spirogyra), anisogamy (Chlamydomonas), oogamy (Volvox, Fucus).

Classes of algae: Chlorophyceae, Phaeophyceae and Rhodophyceae

NCERT section 3.1.1 Chlorophyceae; 3.1.2 Phaeophyceae; 3.1.3 Rhodophyceae (Table 3.1)

Algae are divided on the basis of pigments, stored food, cell wall and flagella.

Chlorophyceae (green algae): unicellular, colonial or filamentous; grass green due to chlorophyll a and b; pigments in definite chloroplasts of various shapes (discoid, plate-like, reticulate, cup-shaped, spiral, ribbon-shaped). Most have pyrenoids (storage bodies of protein and starch). Stored food: starch (some also oil droplets). Cell wall: inner cellulose, outer pectose. Flagella: 2-8, equal, apical. Mostly fresh water. Examples: *Chlamydomonas*, *Volvox*, *Ulothrix*, *Spirogyra*, *Chara*.

Phaeophyceae (brown algae): mainly marine; from simple branched filaments (*Ectocarpus*) to profusely branched kelps up to 100 m tall. Pigments: chlorophyll a, c, carotenoids and xanthophylls; colour from olive green to brown depending on fucoxanthin. Stored food: laminarin or mannitol. Wall: cellulose covered with gelatinous algin. The body has a holdfast (attachment), a stalk (stipe) and a leaf-like frond. Motile cells are pear-shaped with two unequal, lateral flagella. Examples: *Ectocarpus*, *Dictyota*, *Laminaria*, *Sargassum*, *Fucus*.

Rhodophyceae (red algae): red due to r-phycoerythrin; mostly marine, especially in warmer areas; found near the surface and at great depths where little light reaches. Stored food: floridean starch, similar to amylopectin and glycogen. Wall: cellulose, pectin and polysulphate esters. No flagellate stages. Sexual reproduction is oogamous with complex post-fertilisation development. Examples: *Polysiphonia*, *Porphyra*, *Gracilaria*, *Gelidium*.

Worked example

Place each alga in its class and give the pigment and stored food that justify your answer: (a) Fucus (b) Porphyra (c) Spirogyra. (3 marks)

Try it first, then show the solutionSolution

1. (a) Fucus: Phaeophyceae (brown algae); chlorophyll a, c and fucoxanthin; stores laminarin or mannitol. (1)
2. (b) Porphyra: Rhodophyceae (red algae); r-phycoerythrin (with chlorophyll a, d); stores floridean starch. (1)
3. (c) Spirogyra: Chlorophyceae (green algae); chlorophyll a and b; stores starch (pyrenoids in the chloroplasts). (1)

Answer: Fucus: brown (fucoxanthin, laminarin/mannitol); Porphyra: red (phycoerythrin, floridean starch); Spirogyra: green (chlorophyll a, b, starch).

Bryophytes: liverworts and mosses

NCERT section 3.2 Bryophytes (3.2.1 Liverworts, 3.2.2 Mosses)

Bryophytes grow in moist, shaded areas, commonly in hills. They are called amphibians of the plant kingdom because they live on soil but depend on water for sexual reproduction.

Body: more differentiated than algae; thallus-like, prostrate or erect, attached by unicellular or multicellular rhizoids. They lack true roots, stems and leaves but have root-like, stem-like and leaf-like structures. The main plant body is haploid and produces gametes: the gametophyte.

Sex organs are multicellular: male antheridium produces biflagellate antherozoids; female archegonium is flask-shaped and produces a single egg. Antherozoids are released into water, reach the archegonium, and one fuses with the egg to form the zygote. The zygote does not undergo reduction division immediately; it forms a multicellular sporophyte, which is not free-living but attached to the gametophyte and depends on it for food. Some sporophyte cells undergo meiosis to form haploid spores, which germinate into gametophytes.

Importance: some mosses are food for herbivores; *Sphagnum* gives peat, used as fuel and as packing material for living material (it holds water). Mosses and lichens are among the first colonisers of bare rocks, decomposing them and making the substrate suitable for higher plants. Dense mats of mosses reduce rain impact and prevent soil erosion.

Liverworts: grow in moist, shady places (banks of streams, marshy ground, damp soil, tree bark). The body is thalloid (*Marchantia*), dorsiventral and closely appressed to the substrate; leafy members have tiny leaf-like appendages. Asexual reproduction by fragmentation or by gemmae: green, multicellular asexual buds in small receptacles called gemma cups on the thallus. The sporophyte has a foot, seta and capsule.

Mosses: the gametophyte has two stages: (1) protonema, creeping, green, branched and often filamentous, developing directly from a spore; (2) leafy stage, developing from the secondary protonema as a lateral bud, with upright slender axes bearing spirally arranged leaves and multicellular, branched rhizoids. It bears the sex organs. Vegetative reproduction by fragmentation and budding of secondary protonema. The sporophyte (foot, seta, capsule) is more elaborate than in liverworts; spores are dispersed by an elaborate mechanism. Examples: *Funaria*, *Polytrichum*, *Sphagnum*.

Worked example

Why are bryophytes called amphibians of the plant kingdom? Describe the two stages of the gametophyte of a moss. (3 marks)

Try it first, then show the solutionSolution

1. They live on land but need water for the antherozoids to swim to the archegonium for fertilisation. (1)
2. Protonema: the first stage, which develops directly from a spore; it is creeping, green, branched and often filamentous. (1)
3. Leafy stage: develops from the secondary protonema as a lateral bud; it has upright slender axes with spirally arranged leaves, is fixed by multicellular branched rhizoids, and bears the sex organs. (1)

Answer: They need water for fertilisation; moss gametophyte = protonema, then leafy stage bearing sex organs.

Pteridophytes

NCERT section 3.3 Pteridophytes

Pteridophytes include horsetails and ferns. They are used for medicinal purposes and as soil binders, and grown as ornamentals. In evolution, they were the first land plants with vascular tissues (xylem and phloem). They grow in cool, damp, shady places, though some flourish in sandy soil.

Sporophyte: the main plant body is a sporophyte, differentiated into true root, stem and leaves with well-differentiated vascular tissue. Leaves are small (microphylls, as in *Selaginella*) or large (macrophylls, as in ferns).

Spores: sporophytes bear sporangia subtended by leaf-like appendages called sporophylls. In some, sporophylls form compact structures called strobili or cones (*Selaginella*, *Equisetum*). Spore mother cells in sporangia undergo meiosis to form spores.

Gametophyte: the spore germinates into an inconspicuous, small, multicellular, free-living, mostly photosynthetic thalloid gametophyte called the prothallus. It needs cool, damp, shady places, so pteridophytes are restricted to narrow geographical regions. The prothallus bears antheridia and archegonia; water is needed for antherozoids to reach the archegonium. The zygote develops into a multicellular, well-differentiated sporophyte, the dominant phase.

Homospory and heterospory: most pteridophytes produce spores of one kind (homosporous). *Selaginella* and *Salvinia* produce two kinds: large megaspores (female) and small microspores (male), so they are heterosporous. Megaspores give female gametophytes and microspores male gametophytes. Female gametophytes are retained on the parent sporophyte for variable periods, and the zygote develops into a young embryo inside the female gametophyte. This is a precursor to the seed habit, an important step in evolution.

Classes: Psilopsida (*Psilotum*), Lycopsida (*Selaginella*, *Lycopodium*), Sphenopsida (*Equisetum*), Pteropsida (*Dryopteris*, *Pteris*, *Adiantum*).

Worked example

Name the class of pteridophytes to which each belongs, and state whether its leaves are microphylls or macrophylls: (a) Selaginella (b) Dryopteris (c) Equisetum. Which of them bear compact strobili? (3 marks)

Try it first, then show the solutionSolution

1. (a) Selaginella: Lycopsida; small leaves (microphylls). (1)
2. (b) Dryopteris: Pteropsida (a fern); large leaves (macrophylls). (1)
3. (c) Equisetum: Sphenopsida (horsetail). Selaginella and Equisetum bear their sporophylls in compact strobili (cones). (1)

Answer: (a) Lycopsida, microphylls (b) Pteropsida, macrophylls (c) Sphenopsida; Selaginella and Equisetum have strobili.

Gymnosperms

NCERT section 3.4 Gymnosperms

Gymnosperms (*gymnos*: naked; *sperma*: seed) are plants in which the ovules are not enclosed by an ovary wall and remain exposed before and after fertilisation; the seeds are naked.

Body: medium-sized trees or tall trees and shrubs. The giant redwood *Sequoia* is one of the tallest tree species. The tap root is generally present. Roots of some genera have fungal association (mycorrhiza, *Pinus*); in *Cycas*, small specialised coralloid roots are associated with N₂-fixing cyanobacteria. Stems are unbranched (*Cycas*) or branched (*Pinus*, *Cedrus*). Leaves may be simple or compound; in *Cycas* pinnate leaves persist for a few years. Leaves are well adapted to extreme conditions: in conifers, the needle-like leaves reduce surface area, and their thick cuticle and sunken stomata reduce water loss.

Reproduction: gymnosperms are heterosporous; they produce haploid microspores and megaspores in sporangia borne on sporophylls, arranged spirally along an axis to form lax or compact strobili (cones).

• Male cones: microsporophylls with microsporangia; each microspore develops into a male gametophyte, the highly reduced pollen grain, within the microsporangium.
• Female cones: megasporophylls with ovules (megasporangia). The megaspore mother cell in the nucellus divides meiotically to form four megaspores; one develops into the multicellular female gametophyte bearing two or more archegonia. The female gametophyte is retained within the megasporangium.
• Male and female cones may be on the same tree (*Pinus*) or on different trees (*Cycas*).
• Pollination: pollen grains are carried by air currents to the ovule. A pollen tube carries the male gametes to the archegonia, so water is not needed. After fertilisation the zygote develops into an embryo and the ovule into a seed, which is not covered.

Examples: *Cycas*, *Pinus*, *Ginkgo*.

Worked example

Give three adaptations of conifer leaves to dry or cold conditions, and name the special roots of Cycas and their function. (3 marks)

Try it first, then show the solutionSolution

1. Needle-like leaves reduce surface area for water loss. (1)
2. Thick cuticle and sunken stomata further reduce transpiration. (1)
3. Cycas has coralloid roots associated with nitrogen-fixing cyanobacteria. (1)

Answer: Needles, thick cuticle, sunken stomata; coralloid roots with N₂-fixing cyanobacteria.

Angiosperms and the comparison of plant groups

NCERT section 3.5 Angiosperms; Summary

In angiosperms (flowering plants), the pollen grains and ovules develop in specialised structures called flowers, and the seeds are enclosed in fruits (formed from the ovary). They are an exceptionally large group occurring in a wide range of habitats, from the tiny *Wolffia* to *Eucalyptus* trees over 100 m tall. They give us food, fodder, fuel, medicines and many commercial products. They are divided into two classes: dicotyledons (two cotyledons in the seed) and monocotyledons (one cotyledon).

The plant 'ladder' compared:

Feature	Algae	Bryophytes	Pteridophytes	Gymnosperms	Angiosperms
Main body	Thallus	Gametophyte	Sporophyte	Sporophyte	Sporophyte
Vascular tissue	No	No	Yes	Yes	Yes
True roots, stems, leaves	No	No	Yes	Yes	Yes
Water for fertilisation	Yes	Yes	Yes	No	No
Seeds	No	No	No	Naked	In fruit
Archegonia	No	Yes	Yes	Yes	No

Bryophytes, pteridophytes and gymnosperms all bear archegonia (they are sometimes called archegoniates).

Worked example

Use the comparison of plant groups to identify each: (a) the main plant body is a haploid gametophyte, it bears archegonia and has no vascular tissue (b) it has vascular tissue and seeds but no archegonia (c) it has vascular tissue and archegonia, its seeds are not enclosed, and it needs no water for fertilisation. (3 marks)

Try it first, then show the solutionSolution

1. (a) Bryophyte: only bryophytes have a dominant gametophyte together with archegonia. (1)
2. (b) Angiosperm: seeds enclosed in fruits, but no archegonia. (1)
3. (c) Gymnosperm: naked seeds; the pollen tube carries male gametes, so water is not needed. (1)

Answer: (a) bryophyte (b) angiosperm (c) gymnosperm

Plant Kingdom in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Algae: Classes, Pigments and Reproduction
• Alternation of Generations in Plants

Plant Kingdom: key facts

Plant groups in order of complexity

$\text{Algae}\to \text{Bryophytes}\to \text{Pteridophytes}\to \text{Gymnosperms}\to \text{Angiosperms}$

Vascular tissue first appears in pteridophytes; seeds in gymnosperms; fruits in angiosperms.

Algal classes by pigment

$\text{green: chl }a,b;\text{brown: chl }a,c+\text{fucoxanthin};\text{red: chl }a,d+\text{r-phycoerythrin}$

Stored food: starch; laminarin/mannitol; floridean starch.

Moss gametophyte stages

$\text{spore}\to \text{protonema}\to \text{leafy stage (bears sex organs)}$

Leafy stage arises as a lateral bud from secondary protonema.

Spores in pteridophytes

$\text{homosporous: one kind};\text{heterosporous: megaspores}+\text{microspores}$

Heterospory (Selaginella, Salvinia) is a precursor to the seed habit.

Ploidy at a glance

$\text{gametophyte }(n);\text{sporophyte, zygote }(2n);\text{spores, gametes }(n)$

Primary endosperm nucleus in angiosperms is 3n.

Plant Kingdom: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the school exam asks Plant Kingdom

The question patterns to expect, and the method that works for each.

Tricks to remember Plant Kingdom

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Green Starch, Brown Laminarin, Red Floridean

  Stored food: green algae starch; brown algae laminarin or mannitol; red algae floridean starch.

  Use it when: Algal class comparisons.

• Brown = Fucoxanthin, Red = Phycoerythrin

  The colour comes from the extra pigment: fucoxanthin in brown, r-phycoerythrin in red.

  Use it when: Pigment questions.

• Bryophytes = Gametophyte boss; Pteridophytes = Sporophyte boss

  In bryophytes the green plant you see is n; from pteridophytes onwards it is 2n.

  Use it when: Ploidy and dominant phase questions.

• SS heterospory

  Selaginella and Salvinia are the two heterosporous pteridophytes to quote.

  Use it when: Examples of heterospory.

• Cycas Coralloid, Pinus Partner (mycorrhiza)

  Cycas roots host cyanobacteria; Pinus roots host fungi.

  Use it when: Gymnosperm root questions.

Plant Kingdom: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section E style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 4-mark question split into 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Plant Kingdom

The slips examiners see most often, and what to write instead.

• ✗Mistake: Calling the moss plant a sporophyte

  The visible plant is assumed to be 2n as in flowering plants.

  ✓Do this: In bryophytes the main plant is the haploid gametophyte; the sporophyte is attached and dependent.

  Usually costs: 1 mark.

• ✗Mistake: Giving flagella to red algae

  Students generalise from green algae.

  ✓Do this: Red algae have no flagellate stages.

  Usually costs: ½-1 mark.

• ✗Mistake: Writing that gymnosperms need water for fertilisation

  Archegonia are linked to water in bryophytes.

  ✓Do this: Gymnosperms use pollen tubes; water is not needed.

  Usually costs: 1 mark.

• ✗Mistake: Wrong ploidy of the prothallus

  It is mistaken for a sporophyte stage.

  ✓Do this: Prothallus (fern gametophyte) is haploid (n).

  Usually costs: ½ mark.

• ✗Mistake: Writing 'ovary' for gymnosperms

  Angiosperm terms are mixed in.

  ✓Do this: Gymnosperms have exposed ovules on megasporophylls; there is no ovary.

  Usually costs: 1 mark.

NCERT exercise guide: Plant Kingdom

What each exercise in the NCERT chapter tests, how to approach it, and a question of the same kind solved step by step. Questions here are written in our own words.

Practice questions on Plant Kingdom

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Which of the following has coralloid roots?
   (a) Pinus (b) Cycas (c) Ginkgo (d) Selaginella

   Hint

   Associated with cyanobacteria.

   Answer

   (b) Cycas

2. Q2 · 1 mark · MCQExam level

   The main plant body of a moss is:
   (a) sporophyte (b) gametophyte (c) protonema only (d) prothallus

   Hint

   Haploid dominant.

   Answer

   (b) gametophyte

3. Q3 · 2 marks · Very short answerExam level

   What is the difference between artificial and natural systems of classification? (2 marks)

   Hint

   Number and type of characters.

   Answer

   Artificial systems used a few superficial morphological characters (e.g. stamens) (1); natural systems used natural affinities based on many characters including anatomy, embryology and phytochemistry (1).

4. Q4 · 2 marks · Very short answerHarder exam level

   Give the cell wall composition and flagella of green algae. (2 marks)

   Hint

   Two layers.

   Answer

   Cell wall: inner layer of cellulose and outer layer of pectose (1). Flagella: 2-8, equal, apical (1).

5. Q5 · 2 marks · Very short answerHarder exam level

   Which of these bear archegonia: Spirogyra, Marchantia, Selaginella, Cycas, mango? Which of the archegonium-bearing ones need water for fertilisation? (2 marks)

   Hint

   Archegoniates are bryophytes, pteridophytes and gymnosperms.

   Answer

   Marchantia, Selaginella and Cycas bear archegonia; Spirogyra (alga) and mango (angiosperm) do not (1). Marchantia and Selaginella need water; Cycas does not, because a pollen tube carries the male gametes (1).

6. Q6 · 3 marks · Short answerHarder exam level

   Suppose a student finds a green, ribbon-like, branched plant on a wet wall with small cups on its surface. (a) Identify it. (b) What do the cups contain and how do they help? (3 marks)

   Hint

   Liverwort.

   Answer

   (a) A liverwort such as Marchantia (1). (b) Gemma cups contain gemmae, green multicellular asexual buds (1); they detach and grow into new plants, spreading the liverwort vegetatively (1).

7. Q7 · 3 marks · Short answerHarder exam level

   How do numerical taxonomy, cytotaxonomy and chemotaxonomy help in modern classification? (3 marks)

   Hint

   One line each.

   Answer

   Numerical taxonomy: computer analysis of all observable characters given equal weight (1). Cytotaxonomy: chromosome number, structure and behaviour (1). Chemotaxonomy: chemical constituents of plants (1).

8. Q8 · 3 marks · Short answerHarder exam level

   Why are pteridophytes considered more advanced than bryophytes? Give three reasons. (3 marks)

   Hint

   Vascular tissue and dominant phase.

   Answer

   They have vascular tissue (xylem and phloem) (1); the dominant plant is an independent sporophyte with true roots, stems and leaves (1); some are heterosporous, a step towards seeds (1).

9. Q9 · 2 marks · Very short answerHarder exam level

   Arrange the following in increasing complexity and state the key new feature at each step: angiosperms, algae, pteridophytes, bryophytes, gymnosperms. (2 marks)

   Hint

   Thallus → embryo → vascular → seed → fruit.

   Answer

   Algae → bryophytes (land, embryo, archegonia) → pteridophytes (vascular tissue) → gymnosperms (naked seeds) → angiosperms (flowers and fruits) (2).

10. Q10 · 3 marks · Short answerHOTS / competency

    Suppose a botanist finds a plant that has seeds but no fruit, and pollen carried by wind to exposed ovules on scale-like leaves arranged in cones. Which group is it? Why can it live in dry places where ferns cannot? (3 marks)

    Hint

    No swimming sperm needed.

    Answer

    Gymnosperm (1). Pollen is carried by wind and the pollen tube delivers male gametes, so no water is needed for fertilisation (1); xerophytic leaves (needles, thick cuticle, sunken stomata) reduce water loss (1).

11. Q11 · 5 marks · Long answerHOTS / competency

    (a) Explain the evolutionary importance of heterospory. (b) Describe how the female gametophyte of a gymnosperm differs from that of a fern. (c) Why are seeds better than spores for survival on land? (5 marks)

    Hint

    Retention and protection.

    Answer

    (a) Heterospory separates male and female functions and allows the female gametophyte to be retained on the sporophyte, the start of the seed habit (2). (b) Fern prothallus is free-living and photosynthetic; the gymnosperm female gametophyte stays inside the ovule (megasporangium) and is nourished by the parent (1). (c) A seed contains an embryo with stored food and a protective coat, can stay dormant and be dispersed, unlike a single-celled spore (2).

12. Q12 · 1 mark · Assertion-reasonHOTS / competency

    Assertion (A): Red algae can grow at greater depths than green algae.
    Reason (R): Red algae contain r-phycoerythrin, which can absorb the blue-green light that penetrates deep water.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

    Hint

    Depth and light.

    Answer

    (a)

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Name a unicellular alga used as food supplement by space travellers.Show answer

   Chlorella.

2. 2.Which algae give algin and carrageen?Show answer

   Brown algae give algin; red algae give carrageen.

3. 3.What are pyrenoids?Show answer

   Storage bodies in chloroplasts of green algae, containing protein and starch.

4. 4.Name the parts of a brown alga's body.Show answer

   Holdfast, stipe and frond.

5. 5.What are gemmae?Show answer

   Green, multicellular asexual buds in gemma cups of liverworts.

6. 6.What is the first stage of a moss gametophyte called?Show answer

   Protonema.

7. 7.Which plants first had vascular tissue?Show answer

   Pteridophytes.

8. 8.What is a strobilus?Show answer

   A compact cone of sporophylls, e.g. in Selaginella and Equisetum.

9. 9.Name one of the tallest tree species.Show answer

   Sequoia (giant redwood), a gymnosperm.

10. 10.Name the smallest angiosperm mentioned by NCERT.Show answer

    Wolffia.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you explain why Linnaeus's system was artificial?
• ☐Can you compare the three algal classes on four features?
• ☐Can you give two economic uses each of algae and gymnosperms?
• ☐Can you explain why bryophytes are called amphibians of the plant kingdom?
• ☐Can you describe the two stages of a moss gametophyte?
• ☐Can you define heterospory and explain its significance?
• ☐Can you state the ploidy of protonema, prothallus, gemma and zygote?
• ☐Can you give three differences between gymnosperms and angiosperms?

Plant Kingdom: frequently asked questions