NCERT solutions for class 11 biology chapter 3 Plant Kingdom

Q1. What is the basis of classification of algae?

Answer:

Algae are chlorophyll-containing thallus-bearing plants characterised by the absence of

embryo stage. A variety of algae are found in a variety of habitats. The various types of

algae are classified on the basis of their pigments, flagellation and the reserve food

material. Based on these criteria, algae are of three types i.e. red algae, brown algae

and green algae.

Feature Chlorophyceae Phaeophyceae Rhodophyceae

Pigment Chlorophyll a

and b

Chlorophyll a, c

and

fucoxanthin

Chlorophyll a, b

and

phycoerythrine

Reserve

food

material

Starch Mannitol and

laminarin

Floridean

starch

Cell wall

composition

Cellulose Cellulose and

algin

Cellulose and

pectin

Flagella 2-8, equal and

apical

2, unequal and

lateral

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Q2. 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:

In the life cycle of a liverwort reduction division take place in the capsule for the

formation of haploid spores that will grow into gametophytic thallus after germination. In

mosses, the gametes fertilise and a zygote is formed. The zygote develops into the

sporophyte. In the capsule of the sporophyte, reduction division takes place and haploid

spores are formed which on germination give rise to gametophytic thallus. In ferns,

reduction division takes place in the sporangia present on leaves for the production of

spores. Gymnosperms, which have sporophytic plant body show reduction division in

their microsporangia and megasporangia for the formation of microspores and

megaspores. In the case of angiosperms, the main plant body is diploid and reduction

division occurs for the formation of gametes. Therefore, in the life cycle of an

angiosperm, reduction division takes place in the anther and ovary at the time of

microspore and megaspore formation respectively.

Q4. 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 ferm; gemma cell in Marchantia;

meristem cell of monocot, ovum of a liverwort, and zygote of a fern.

Answer:

Tissue Ploidy

Protonemal cell of a moss; Haploid

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Primary endosperm nucleus in dicot, Triploid

Leaf cell of a moss Haploid

Prothallus cell of a fern Haploid

Gemma cell in Marchantia; Haploid

Meristem cell of monocot Diploid

Ovum of a liverwort Haploid

Zygote of a fern Diploid

Q5. Write a note on economic importance of algae and gymnosperms.

Answer:

Economic importance of algae

1. Green algae such as Ulva, Caulerpa, Enteromorpha, Chlorella etc are used as food

rich in lipid, protein, vitamins, minerals etc.

2. Chlorella and Caulerpa are used to obtain antibiotics also.

3. A number of green algae such as Chlamydomonas, Chlorella, Scenedesmus etc are

used in sewage oxidation tanks.

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Economic importance of Gymnosperms

1. The seeds of Pinus gerardiana are roasted and eaten.

2. The softwood of gymnosperms is used in the construction of furniture, plywood,

packing cases, match sticks, railway sleepers etc.

3. The wood from Picea, Pinus, Larix and Abies is used in the manufacture of paper.

4. Pine needles are used to make fibre boards.

5. Resins containing terpenes, resin acids and esters can be obtained from

gymnosperms. Resins are used in waterproofing, sealing joints etc.

6. A drug called ephedrine is extracted from Ephedra which is a gymnosperm. This drug

is useful in respiratory ailments such as asthma.

Q6. Both gymnosperms and angiosperms bear seeds, then why are they classified

separately?

Answer:

Both gymnosperms and angiosperms come under the group spermatophyta or seed-

bearing plants. However, angiosperms and gymnosperms are classified separately in

spermatophyta because gymnosperms possess naked seeds i.e. their seeds are not

enclosed in ovary whereas angiosperms possess seeds that are enclosed in the ovary.

Q7. What is heterospory? Briefly comment on its significance. Give two examples.

Answer:

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Heterospory- It refers to the existence of two types of meiospores i.e. microspores and

megaspores in a single plant. These microspores and megaspores are formed

respectively within microsporangia and megasporangia which in turn are borne on two

distinct sporophylls called microsporophylls and megasporophylls respectively. The

microspores and megaspores upon germination give rise to male and female

gametophyte respectively. The megaspore is retained in megasporangia and it ensures

proper development of the zygote. which is formed after the fusion of microgametes

with the megagametes. The zygote is retained on the plant and it is considered to be a

precursor of seed habit.

Significance of heterospory- Heterospory is considered to be an important step in

evolution as it is a precursor of seed habit which is seen in higher plants. Heterospory

was first observed in pteridophyte Selaginella and Salvinia .

NCERT solutions for class 11 biology chapter 3 plant kingdom:

Q8. Explain briefly the following terms with suitable examples:-

(1) protonema

Answer:

Protonema- It refers to the creeping, green, branched, often filamentous structure which

is formed directly after the germination of moss spore. It represents the first stage in the

life cycle of moss. Protonema is short-lived and it grows prostrate on the surface.

Protonema bears rhizoids for the absorption of materials.

Q8. Explain briefly the following terms with suitable examples

(2) antheridium

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Answer:

Antheridium- It is the male sex organ found in bryophytes, pteridophytes and some

algae. Antheridium encloses a mass of cells that give rise to male gametes. Generally,

antheridium, remain enclosed by a jacket of sterile cells.

Q8. Explain briefly the following terms with suitable examples

(3) archegonium

Answer:

Archegonium- It is female sex organ found in bryophytes, pteridophytes and

gymnosperms. Based on the presence of archegonium, these three groups are referred

to as archegoniate. It generally possesses a swollen venter and a tubular neck. The

venter possesses ventral canal cells and neck contains neck canal cells. Archegonium

also contains the female gamete which is called egg.

Q8. Explain briefly the following terms with suitable examples

(4) diplontic

Answer:

Diplontic- This is a term utilised for depicting the life cycle of angiosperms and

gymnosperms. In this type of life cycle, the plant body is represented by a diploid plant

i.e. sporophyte. It bears sex organs that produce male and female gamete. The

gametophyte is of reduced type and it is dependent on the sporophyte. The male and

female gametes fuse and form zygote which develops on the diploid plant.

Q 8. Explain briefly the following terms with suitable examples

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(5) sporophyll

Answer:

Sporophylls- These refer to leaf-like appendages bearing sporangia in pteridophytes,

gymnosperms etc. Sporophylls can be either microsporophylls or megasporophylls and

respectively they can form either microsporangia or megasporangia.

Q8. Explain briefly the following terms with suitable examples

(6) isogamy

Answer:

Isogamy- It refers to the process of fertilisation of two gametes which are exactly similar

to each other in morphology, physiology, anatomy etc. Such gametes are called

isogametes.

Solutions for NCERT lass 11 biology chapter 3 plant kingdom:

Q9. Differentiate between the following:-

(i) red algae and brown algae

Answer:

Differences between red algae and brown algae are as follows:

Red algae Brown algae

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Red algae possess chlorophyll

a, d and phycoerythrin

Brown algae consist of

chlorophyll a, c and fucoxanthin

They contain floridean starch as

reserve food material

Brown algae contain laminarin

and mannitol as reserve food

material

Cell walls are composed of

cellulose, pectin and

phycocolloids

The cell wall is composed of

cellulose and algin

Red algae due to the presence

of red pigment phycoerythrin,

are grouped under

Rhodophyceae

Brown algae due to the

presence of fucoxanthin a brown

pigment is grouped under

Phaeophyceae

Q9. Differentiate between the following:- (ii) liverworts and moss

Answer:

Differences between liverworts and mosses are as follows

Liverworts Mosses Aakas

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Sporophyte has very little

photosynthetic tissue, so it is

completely parasitic on the

gametophyte

Sporophyte contains

more photosynthetic

tissue

Scales often present Scales are mostly

absent

Gemma cups are present for vegetative

reproduction in some liverworts

Gemma cups are mostly

absent

Rhizoids are unicellular Rhizoids are

multicellular

The gametophyte is thalloid with

dichotomous branching

The gametophyte is

leafy, branching is lateral

Q9. Differentiate between the following:- (iii) homosporous and heterosporous

pteridophyte

Answer:

Homosporous

pteridophytes

Heterosporous pteridophytes Aakas

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These pteridophytes

produce only a single type

of spores, hence are called

homosporous

pteridophytes

These pteridophytes produce two

types of spores i.e. microspores and

megaspores. Hence, they are called

heterosporous pteridophytes

The produce only a single

gametophyte which is

bisexual.

They further form two types of

gametophytes i.e microgametophytes

and megagametophytes.

Q9. Differentiate between the following:- (iv) syngamy and triple fusion

Answer:

The differences between syngamy and triple fusion are as follows:

Syngamy Triple fusion

It refers to the fusion of

male gamete with female

gamete i.e egg cell in

angiosperms is called

syngamy

It refers to the fusion of second male

gamete with the 2 polar nuclei of the

central cell. Since, in this fusion, 2

polar nuclei and one sperm nuclei

fuse, its called triple fusion

The end product is zygote

which is a diploid structure

The end product is the primary

endosperm nuclei which are triploid.

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Q10. How would you distinguish monocots from dicots?

Answer:

Differences between monocots and dicots are as follows:

Monocots Dicots

Monocots possess seeds with a

single cotyledon

Dicots bear seeds with two

cotyledons

Monocots possess isobilateral

leaves

Dicots possess dorsiventral

leaves

The flowers of monocots are

generally trimerous i.e. the

number of sepals, petals,

stamens and pistil is in the

multiples of three in these

plants

The flowers of dicots are

pentamerous i.e. the number of

sepals, petals, stamens and

pistils are in the multiples of five

in these plants.

They have fibrous roots They have tap roots

Cambium is absent in these

plants

Cambium is present in these

plants

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NCERT solutions for class 11 biology chapter 3 plant kingdom:

Q11. Match the following (column I with column II)

Column I Column II

(a) Chlamydomonas (i) Moss

(b) Cycas (ii) Pteridophyte

(c) Selaginella (iii) Algae

(d) Sphagnum (iv) Gymnosperm

Answer:

Correct matching is (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)

Column I Column II

(a) Chlamydomonas (iii) Algae

(b) Cycas (iv) Gymnosperm

(c) Selaginella (ii) Pteridophyte

(d) Sphagnum (i) Moss

Q12. Describe the important characteristics of gymnosperms.

Answer:

Important characteristics of gymnosperms

1. Gymnosperms are seed plants in which the seeds remain exposed over the surface

of megasporophylls.

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2. Gymnosperms are represented by 900 living species.

3. Gymnosperms are perennial and woody plants (either trees or bushes). The xylem of

gymnosperms does not possess vessels except in Gnetum. Phloem is without

companion cells and sieve tubes.

4. Two types of sporophylls occur in gymnosperms. These are microsporophylls and

megasporophylls. The microsporophylls aggregate to form male strobili or cone while

megasporophylls aggregate to form female strobili or cone. Microsporangia and

megasporangia are borne on microsporophylls and megasporophylls respectively.

4. Microsporangia give rise to microspores or pollen grains whereas megasporangia

forms megaspores. The male and female gametophytes are formed within micropores

and megaspores.

5. Female gametophyte contains archegonia. The male gametophyte produces only two

male gametes or sperms.

6. The pollination is direct and is accomplishes by wind i.e. anemophily. A pollen tube is

formed in gymnosperms. it is called as siphonogamy.

7. Seeds contain endosperm.

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