Plant Kingdom Class 11 Biology Notes and Questions

Notes Class 11 Revision Notes

Please refer to Plant Kingdom Class 11 Biology notes and questions with solutions below. These revision notes and important examination questions have been prepared based on the latest Biology books for Class 11. You can go through the questions and solutions below which will help you to get better marks in your examinations.

Class 11 Biology Plant Kingdom Notes and Questions

Points to Remember

Classification :

Artificial System of Classification

  • By Carolus Linnaeus, based on androecium structure and vegetative characters.

Natural System of Classification

  • Based on natural affinities among organisms
  • Included external as well as internal features
  • By Geroge Bentham and J.D. Hooker

Phylogenetic System of Classfication

  • Based on evolutionary relationships between the various organisms
  • By Engler and Prantl
  • Later on By Hutchinson

Numerical Taxonomy:

  • Carried out using computers
  • Based on all observable characteristics
  • Data processed after assigning number and codes to all the characters.
    Advantages : Each character gets equal importance and a number of characters can be considered.

Cytotaxonomy :

  • Based on cytological informations.
  • Gives importance to chromosome number, structure and behaviour.

Chemotaxonomy :

  • Based on Chemical constitutents of the plants.


  • Chlorophyll bearing, simple, thalloid, autotrophic and largely aquatic orgamsms.

Importance of Algae :

  • Help in carbon dioxide fixation by carrying out photosynthesis and have immense economic importance.
  • At least half of the total carbon dioxide fixation on earth carried out by them.
  • Increases dissolved oxygen level in their environment.
  • Many species like Laminaria, Sargassum, Porphyra etc. are used as food.
  • Agar obtained from Gelidium and Gracilaria which is used in ice-creams and jellies and to grow microbes.
  • Algin obtained from brown algae and carrageen from red algae used commercially as hydrocolloids.
  • Chlorella and Spirullina are unicellular algae, rich in protein and used even by space travellers.
  • Algae are unicellular like Chlamydomonas, colonial like Volvox or or filamentous like spirogyra and Ulothrix. Occur in water, soil, wood moist stones etc.

Algae are divided into 3 classes.

(i) Chlorophyceae

  • Green algae, Main pigment is chlorophyll ‘a’ and ‘b’.
  • Cell wall has inner layer of cellulose and outer layer of pectose.
  • Has pyrenoids made up of starch and proteins.
  • Pigment and pyrenoids are located in Chloroplast.
    e.g., Chlamydomonas, Volvax, Spirogyra, Ulothrix, Chara.

(ii) Phaeophyceae

  • Brown algae are brown coloured due to main pigments chlorophyll ‘a’, ‘c’ and fucoxanthin (xanthophyll)
  • Cell wall has cellulose with gelantionous coating of algin.
  • Has mannitol and laminarin (complex carbohydrate) as reserve food material.
  • Body divisible into holdfast, stipe and frond.
  • e.g., Ectocarpus, Fucus, Laminaria, Dictyota, Sargassum

(iii) Rhodophyceae

  • Red algae are red coloured due to pigments chlorophyll ‘a’, ‘d’ and r-phycoerythrin.
  • Found on surface as well great depths in oceans.
  • Cell wall has cellulose.
  • Reserve food material is ftoridean starch.
  • e.g.,Polysiphonia, Porphyra, Gelidium,Gracilaria.

Reproduction in Algae

Vegetative rept·oduction : by fragmentation

Asexual Rept·oduction : Flagellated zoospores m Chlorophyceae, Biftagellated zoospores in Phaeophycease, By non-motile spores in Rhodophyceae.

Sexual Reproduction : Isogamous, anisogamous or oogamous in chlorophyceae and Phaeophyceae.

By non-motile gametes and oogamous in Rhodophyceae.

Bryophytes :

  • ‘Amphibians of plant kingdom’.
  • Occur in damp, humid and shaded places.
  • Lack true roots, stem or leaves.
  • Main plant body is haploid and thallus like (prostrate or erect)
  • Economic Importance: Food for herbaceous animals.
    Sphagnum in from of peat is used as fuel and also used as packing material for trans-shipment of living material, as it has water holding capacity.
    Prevents soil erosion, alongwith lichens are first colonizers on barren rock.
  • Is divided into two classes Liverworts (thalloid body, dorsiventral, e.g., Marchantia) and Mosses (have two stages in gametophyte-creeping, green, branched, filamentous protonema stage and the leafy stage having spirally arranged leaves e.g., Funaria, Polytrichum and Sphagnum).

Reproduction in Bryophytes

  • Vegetative reproduction by fragmentation.
  • Asexual reproduction by gemmae formed in gemma cups.
  • Sexual reproduction : Main plant body is haploid, produces gametes and so called Gametophyte. By fusion of antherozoids produced in antheridium and egg cell produced in archegonium, results in formation of zygote which develops into sporophytic structure differentiated into foot, seta and capsule. Spores produced in a capsule germinate to from free-living gametophyt e (Protonema). Sporophyte is not free living but attached to photosynthetic gametophyte from which derives nutrition.

Pteridophytes :

  • First terrestrial plants.
  • Prefer cool, damp and shady places to grow.
  • Grown as ornamentals.
  • Used for medicinal purpose, as soil binder.
  • Main plant body is sporophyte which is differentiated into true root, stem and leaves.
  • Leaves may be small as in Selaginella or large as in ferms.
  • Sporangia having spores are subtended by leaf-like appendages called sporophylls. (Sporphylls may be arranged to form strobili or cones.)
  • In Sporangia, the spore mother cells give to spores after meiosis.
  • Spores germinate to form haploid gametophytic structure called prothallus which is free living, small, unicellular and photosynthetic.
  • Prothallus bears antheridia and archegonia which bear antherozoids and egg cell respectively which on fertilisation from zygote. Zygote produces multicellular, well differentiated sporophyte.
  • The four classes are : Psilopsida (Psilotum), Lycopsida (Selaginella), Sphenopsida (Equisetum) and Pteropsida (Pteris).

    Heterospory :
     Two kinds of spores i.e., large (macro) and small (micro) spores are produced. e.g.,Selaginella and Salvinia.

    Seed Habit :
     The development of zygote into young embryos takes place within the female gametophyte which is retained on parent sporophyte. This event is precursor to seed habit and this is an important step in evolution and is found Selaginella and Salvinia among the pteridophytes.

Gymnosperms :

  • Have naked seeds as the ovules are not enclosed by any ovary wall and remain exposed.
  • Includes shrubs and trees (medium and tall sized).
  • Have generally tap roots, stem may be unbranched (Cycas) or branched (Pinus, Cedrus), leaves-needle like (Pinus) and pinnate (Cycas).
  • Roots of Pinus have fungal association in the form of mycorrhiza.
  • Cycas have small specialized roots called coralloid root which are associated with N2 fixing cyanobacteria.
  • Heterosporous-Produce haploid microspores and megaspores.
  • Male cone has microsporophylls which bear microsporangia having microspores which develop into reduced gametophyte called pollengrain.
  • Female cone has megasporophylls which bear megasporongia having megaspores which are enclosed within the megasporangium (Nucellus). One megaspore develops into female gametophyte bearing two or more archegonia.
  • Pollen grains carried in air currents reach ovules, form pollen tube which reach archegonia and release male gametes which fertilise egg cell and form zygote which produce embryos. Ovules develop into seeds which are not covered.

Angiosperms :

  • Called flowering plants and have seeds enclosed in fruits.
  • Divided into two classes-Dicotyledons (have two cotyledons) and Monocotyledons (have one cotyledon).
  • Smallest angiospet·m :Wolfia
  • Large tree Eucalyptus (Over 100 meters)
  • Stamen has filament and anther. Anthers bear pollen grains. Pollen grains have two male gametes.
  • Pistil has stigma, style and ovary. Ovary has ovule in which female gametophyt e (embryo sac) develops.
  • Embryo sac has 7 cells and 8 nuclei.One egg cell 2 synergids, 3 antipodals and two polar nuclei which fuse to form secondary nucleus.
  • Pollen grain is carried by wind, water, insects and other agents reaches to stigma and produces pollen tube which enters embryo sac.
  • Double fertilisation : One male gemate fuses with egg cell (Syngamy) to form zygote which develops into embryo.
    Other male gamete fuses with secondary nucleus (triple fusion) which forms triploid primary endosperm nucleus (PEN). PEN develops into endosperm which nourishes the developing embryo.
  • Ovules develop into seeds and ovaries into fruits.



• where sporophyte becomes the main plant body
• where main plant body (sporophyte) is truly differentiated into true root, stem and leaves.
• Possess well-differentiated vascular tissues.
o The sporophytes bear sporangia which produce spores.
o The spores germinate to form gametophytes
• which require cool, damp places to grow.

o The gametophytes bear male and female sex organs called antheridia and archegonia, respectively.
o Water is required for transfer of male gametes to archegonium (restriction for distribution) where zygote is formed after fertilisation.
o The zygote produces a sporophyte.
o Microphylls (small leaf) is found in selaginella
o Macrophylls (large leaf) are found in fern.
o Sporophylls are sporangia bearing leaf.
o In some pteridophytes, Sporophylls are compactly arranged and form cone or strobilus.
o Cones are found in Equisetum and selaginella.
o Sporangia either produce
• only one type of spores i.e. HOMOSPOROUS
• Two types of spores i.e. HETEROSPOROUS.

o HETEROSPOROUS pteridophytes
• Megaspore which germinate to form female gametophyte
• Microspore germinate to form male gametophyte.

o Selaginella and salvinia is example of heterospory.
o The female gametophyte in HETEROSPOROUS PTERIDOPHYTE are retained on the parent sporophytes for variable periods.
• The development of the zygotes into young embryos take place within the female gametophytes.
• This event is a precursor to the seed habit considered an important step in evolution.

o Inside sporangia, spore mother cell produces haploid spores after meiosis.
o This spore germinates to form haploid inconspicuous, small but multicellular free-living, mostly photosynthetic thalloid gametophytes called prothallus.
o These gametophytes require cool, damp, shady places to grow.
(require water for fertilization).

o The pteridophytes are further classified into four classes:
• Psilopsida (Psilotum);
• Lycopsida (Selaginella, Lycopodium),
• Sphenopsida (Equisetum) and
• Pteropsida (Dryopteris, Pteris, Adiantum).

o Main plant body is sporophyte.
o Tap root system.
o Roots in some genera have fungal association in the form of mycorrhiza (Pinus)
o In some others (Cycas) small specialised roots called coralloid roots are associated with N2- fixing cyanobacteria.
o Cycas has unbranched stem.
o Pinus & cedrus have branched stem.
o The leaves in gymnosperms are well-adapted to withstand extremes of temperature, humidity and wind.
o In conifers(Pinus), the needle-like leaves reduce the surface area.
• thick cuticle and sunken stomata also help to reduce water loss.

o All gymnosperms are heterosporous
• they produce haploid microspores and megaspores.
o The two kinds of spores are produced within sporangia that are borne on Sporophylls
o These Sporophylls are compactly & spirally arranged in cone/strobilus.
o The strobili bearing microsporophylls and microsporangia are called MALE STROBILI.
o The microspores develop into a male gametophytic generation which is highly reduced and is confined to only a limited number of cells.
o This reduced gametophyte is called a pollen grain.
o The development of pollen grains take place within the microsporangia.
o The cones bearing megasporophylls with ovules(megasporangia) are called FEMALE STROBILI.
o The megaspore mother cell is differentiated from one of the cells of the nucellus.
o The nucellus is protected by envelopes and the composite structure is called an ovule(megasporangium)
o The ovules are borne on megasporophylls
o Megasporophylls clustered to form the female cones.
o The megaspore mother cell divides meiotically to form four megaspores.
o One of the megaspores enclosed within the megasporangium develops into a multicellular female gametophyte that bears two or more archegonia or female sex organs.
o The multicellular female gametophyte is also retained within megasporangium.
o Gametophytes are dependent on sporophyte and don’t have independent existence.
o Pollination by wind
o Pollen grain come in contact with the opening of the ovules borne on megasporophylls.
o The pollen tube carrying the male gametes grows towards archegonia in the ovules and discharge their contents near the mouth of the archegonia.
o Water is not required for fertilization.
o Following fertilisation, zygote develops into an embryo and the ovules into seeds.
o Endosperm is haploid and before fertilization structure.
o These seeds are not covered i.e. naked seed (seeds are not enclosed in fruit because ovary is absent in gymnosperm).
o Pinus is a monoecious
• Microsporangia and megasporangia born on same plant.

o Cycas is dioceous plant
• Microsporangia and megasporangia born on different plants.

o Life cycle is DIPLONTIC.

• They were based mainly on
• vegetative characters
• on the reproductive structure
• Superficial morphological characteristics
• Mistake → They separated the closely related species.

• Why → The vegetative characters are more easily affected by environment.
• Linnaeus used androecium morphology for classification of plant.
• It was based on natural affinities among the organisms as well as internal features, like ultrastructure, anatomy, embryology and phytochemistry.
• Bentham & Hooker proposed this system.
o It is based on evolutionary relationships between the various organisms.
o Presently acceptable system.
o This assumes that organisms belonging to the same taxa have a common ancestor.

4. In absence of fossil evidences, taxonomist take help from various branch to solve the problems in classification .

o It stores computerised data of all observable characters.
o Number and codes are assigned to all the characters and the data are then processed.
o In this way each character is given equal importance and at the same time hundreds of characters can be considered.

6. Cytotaxonomy that is based on cytological information like chromosome number, structure, behaviour.

7. Chemotaxonomy that uses the chemical constituents of the plant to resolve confusions.

o The pollen grains and ovules are developed in specialised structures called flowers.
o The seeds are enclosed by fruits.
o The angiosperms are an exceptionally large group of plants occurring in wide range of habitats.
o They provide us with food, fodder, fuel, medicines and several other commercially important products.
o Wolfia is smallest angiosperm plant.
o In angiosperms, the male sex organs (stamen) and female sex organs (pistil) are borne in a flower.

9. One male gamete fuses with egg cell (syngamy) and other fuses with diploid secondary nucleus (triple fusion). This phenomenon of two fusions is called double fertilisation and is unique to angiosperms.

10. Endosperm is triploid & post fertilization structure.

11. The angiosperms are divided into two classes – the dicotyledons and the monocotyledons.

o Alternate occurrence of gametes producing gametophyte and spore producing sporophyte in LIFE-CYCLE is called ALTERNATION OF GENERATIONS.

13. HAPLONTIC life cycle
o the main plant body is gametophyte(n),
o zygote is the only diploid in its life cycle
o characterised by ZYGOTIC MEIOSIS.
o EXAMPLES: volvox, spirogyra and some species of chlamydomonas.

o Here, main plant body is diploid sporophyte.
o Sporic meiosis.
o Haploid gametophytes are very reduced type(one to few celled).
o Examples: Gymnosperm, Angiosperm and fucus (brown algae).

o In this type of life cycle, plants exhibit an intermediate condition both phases are multicellular.
o Bryophytes and pteridophyte are the examples.
o In bryophyte, gametophyte is dominant whereas in Pteridophyta, sporophyte is dominant.
o Sporic meiosis.

16. Pteridophyte is the group where gametophyte and sporophyte both are independent and free living.

17. Ectocarpus, kelp (brown algae), polysiphonia (red algae) show haplo-diplontic life cycle.

18. Algae is the group in plant kingdom which show all three type of alternation of generations.


1. Kingdom plantae of Whittaker’s classification has
o Algae,
o Bryophyta,
o Pteridophyta,
o Gymnosperm &
o Angiosperm.

2. Plants are
o autotrophic (chlorophyll bearing),
o eukaryotic,
o Having cellulosic cell wall,
o Tissue/organ level body organization.

o chlorophyll-bearing, autotrophic
o Simple, Thalloid Body
o Largely aquatic organisms.
o Thallus means plant body is not differentiated into root, stem and leaf.
o Lichen is symbiotic association of algae with fungi.
o Algae also show symbiotic relationship with sloth bear.
• Algae provide camouflage & mineral nutrition to bear whereas sloth bear give shelter and water.

o Chlamydomos is microscopic unicellular. (now in Protista)
o Colonial form-volvox (green algae)
o Filamentous form-ulothrix and spirogyra (green algae).
o Kelp (brown algae) form massive plant body.
o Algae usually reproduce vegetative by fragmentation.
o Asexual reproduction by formation of different types of spores (mainly through zoospore i.e. having flagella).
o Sexual reproduction by formation of gametes
• isogamy, anisogamy or oogamy.
• Chlamydomonas (motile gametes), spirogyra (non-motile gametes) both show isogamy.
• Some species of chlamydomonas also show Anisogamy
• Volvox and Fucus show oogamy
o Depending on the type of pigment possessed and the type of stored food, algae are classified into three main classes,
•  Chlorophyceae,
•  Phaeophyceae and
•  Rhodophyceae.

o Lamanaria, sargassum and porphyra (brown algae) are used as food.
o 70 species of marine algae are used as food.
o About 50% of the world’s photosynthesis is done by algae
•  Increase the level of dissolved O2 in their immediate environment.

o Important primary producers
•  form the basis of the food chain of all aquatic animals.

o Agar(commercial products) obtained from Gelidium and Gracilaria
•  used to grow microbes
•  used in preparations of ice-creams and jellies.

o Algin (from brown algae) and carrageen (from red algae) which are used commercially for their water holding capacity.
o Chlorella a unicellular alga rich in proteins is used as food supplement even by space travellers.

4. CHOLOROPHYCEAE (Green algae):
o Main pigment à chlorophyll a and b.
o Stored food à starch.
o Have one or more storage bodies à pyrenoids
•  located in the chloroplasts.
•  Pyrenoids contain protein besides starch.

o Green algae usually have a rigid cell wall
• made of an inner layer of cellulose and an outer layer of pectose

o Number of flagella in motile cell à 2-8
•  they are equal in size and apical in position.

o Vegetative reproduction à by fragmentation.
o Asexual reproduction à flagellated zoospores
o produced in zoosporangia.
o The sexual reproduction à isogamous, anisogamous or oogamous.
o Example of green algae à

• Chlamydomonas,
•  Volvox,
•  Ulothrix,
•  Spirogyra and
•  Chara

o Volvox, spirogyra and some species of chlamydomonas show haplontic life (zygotic meiosis) cycle
•  main plant body is gametophyte
• the only diploid cell in their life cycle is zygote.

o Main pigments à chlorophyll a and c and fucoxanthin (brown colour).
o Food is stored as complex carbohydrates à Laminarin or Mannitol.
o The vegetative cells have a cellulosic wall usually covered on the outside by a gelatinous coating of algin.
o The plant body is usually attached to the substratum by a holdfast, and has a stalk, the stipe and leaf like photosynthetic organ – the frond.
o Vegetative reproduction takes place by fragmentation.
o Asexual reproduction in most brown algae is by biflagellate zoospores.
o Motile cells (zoospores and gametes) are pyriform and have two unequal laterally inserted flagella.
o Sexual reproduction may be isogamous, anisogamous or oogamous.
o The common examples are :
• Ectocarpus,
• Dictyota,
• Laminaria,
• Sargassum and
• Fucus.

o Kelp belongs to brown algae.
o Fucus show DIPLONTIC LIFE CYCLE (sporic meiosis).
o main plant body is diploid.

6. RHODOPHYCEAE (red algae):
o Main pigments are chlorophyll a, d and r-phycoerythrin
o r-phycoerythrin à reason of red colour
o Majority of the red algae are marine
• greater concentrations found in the warmer areas.
• They occur in both well-lighted regions close to the surface of water and also at great depths in oceans where relatively little light penetrates.

o Cell wall is made up of cellulose, pectin and polysulphate esters.
o The food is stored as Floridian starch
• very similar to amylopectin and glycogen in structure.

o The red algae usually reproduce vegetatively by fragmentation.
o Motile cells are completely absent in their life cycle.
o Sexual reproduction is oogamous and accompanied by complex post fertilisation developments.
o The common members are:
• Polysiphonia,
• Porphyra,
• Gracilaria and
• Gelidium.

o Red algae are mainly marine.

o Plants which can live in soil but are dependent on water for sexual reproduction.
• Therefore, their occurrence is limited to cool, damp and shady places.

o Their plant body is more differentiated than that of algae.
o It is thallus-like and prostrate or erect and attached to the substratum by rhizoids.
o Vascular tissue is absent.
o The main plant body of the bryophyte is GAMETOPHYTE (haploid).
• It produces gametes.

o The sex organs in bryophytes are multicellular and jacketed.
o The male sex organ is called antheridium.
o They produce biflagellate anthrozoids.
o The female sex organ called archegonium
• flask-shaped and produces a single egg.

o Sexual reproduction is oogamous.
o Fertilization requires water for anthrozoids movement.
o After fertilization, zygote divide mitotically and produce multicellular embryo which then differentiated as sporophyte.
o Sporophyte is the plant which produce haploid spores by meiosis (sporic meiosis).
o Haploid spores germinate to form gametophyte.
o Sporophyte is dependent upon gametophyte
• for food and nourishment.

o Bryophyte shows alternation of generation
• between gametophyte and sporophyte.

o Life-cycle is haplo-diplontic (sporic meiosis).
o Bryophyta is the first evolved group where embryo formed
o Species of Sphagnum, a moss, provide peat
• that have long been used as fuel,
• as packing material for trans-shipment of living material because of their capacity to hold water.

o Since mosses form dense mats on the soil, prevent soil erosion
o They have great ECOLOGICAL IMPORTANCE as along with lichens they are pioneer of plant succession on bare rock/soil.
• They decompose rocks making the substrate suitable for the growth of higher plants.

o The bryophytes are mainly divided into liverworts and mosses.

o Plant body is dorsiventrally thallod.
• e.g. marchentia

o Leafy members have tiny leaf-like appendages in two rows on the stem-like structures.
o Asexual reproduction
• takes place by fragmentation of thalli,
• by the formation of specialised structures called gemmae.

o Gemmae
• green, multicellular, asexual buds
• develop in small receptacles called gemma cups located on the thalli.
• Become detached and germinate to form new individuals.

o In marchentia,
• anthridia (male sex organ) →
• produce in receptacles called anthridiophore
• archegonia (female sex organ) →
• produce in receptacles called archigoniophore

o The sporophyte is differentiated into a foot, seta and capsule.
o After meiosis, spores are produced within the capsule.
o These spores germinate to form free-living gametophyte.

o Mosses gametophyte has two stage.
o The first stage is the PRIMARY protonema stage, which develops directly from a spore. It is a creeping, green, branched and frequently filamentous stage.
o The second stage is the leafy stage SECONDARY PROTONEMA which develops from the PRIMARY protonema as a lateral bud. They consist of upright, slender axes bearing spirally arranged leaf like structure.
o They are attached to the soil through multicellular and branched rhizoids.
o Secondary protonema bears sex organs.
o Vegetative reproduction
• by fragmentation
• budding in the secondary protonema.

o In sexual reproduction, the sex organs antheridia and archegonia are produced at the apex of the leafy shoots.
o After fertilisation, the zygote develops into a sporophyte,
• consisting of a foot, seta and capsule.

o The sporophyte is more elaborate than that in liverworts.
o The capsule contains spores.
o Spores are formed after meiosis.
o The mosses have an elaborate mechanism of spore dispersal.
o Common examples of mosses are –
• Funaria,
• Polytrichum and
• Sphagnum (peat moss).

Plant Kingdom Class 11 Biology

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