NCERT Solutions For Class 11 | Biology | Chapter 3 | Plant Kingdom

NCERT Class 11 Chapter 3 – Plant Kingdom talks about the different classification of the Plant Kingdom. This includes Algae, Bryophytes, Pteridophytes, Angiosperms & Gymnosperms.

The different types of species are discussed in detail, including information like their lifecycle, behavior, and nature, etc. The solutions of this chapter would help students grasp the concept from the exam perspective.

1. What is the basis of classification of algae?

Answer – Traditionally, algae were classified on the basis of the colour imparted to them by the pigments present. The table below shows this –

ALGAE	COMMON NAME	MAJOR PIGMENTS
CHLOROPHYCEAE	Green Algae	Chlorophyll a, b
PHAEOPHYCEAE	Brown Algae	Chlorophyll a, c and fucoxanthin
RHODOPHYCEAE	Red Algae	Chlorophyll a, d, and phycoerythrin

Presently, characteristics like food stored, nature of cell wall, number of flagella and their positions, and habitat are also used for the classification of algae.

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

Answer – Reduction division take place in the following life stages of –

• LIVERWORT – Reduction division takes place in the spore mother cells in the capsule of the short-lived diploid sporophytes. These spores germinate to form a dominant haploid gametophyte.
• MOSS – Reduction division occurs in the spore mother cells in the capsule of the short-lived diploid sporophytes to form haploid spores.
• FERN – The main body sporophytes in the fern bear sporangia that are subtended by leaf-like appendages called sporophylls. Meiosis occurs in the spore mother cells present in the sporangia to produce haploid spores.
• GYMNOSPERM – the gymnosperm bear microsporangia and megasporangia. Reduction division occurs in two places. In the microsporangia, meiosis occurs in the microspores to produce male gametophyte pollen grains. In the megasporangia, reduction division occurs in the megaspore mother cell to form a multicellular female gametophyte.
• ANGIOSPERM – In the anther of the stamen, meiosis occur in the micropores mother cells to form male gametophyte- pollen grains. In the nucellus of the ovule (megasporangium), meiosis takes place in the megaspore mother cell to form megaspores, which develop into the female gametophyte.

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 PTERIDOPHYTES –

• The dominant phase in the life cycle of pteridophytes is the sporophyte plant body, i.e. diploid.
• The sporophyte bear sporangia where meiosis takes place in spore mother cells to produce spores.
• The spores germinate to form short-lived, small but multicellular free-living gametophytes called prothallus.
• The gametophytes bear male and female sex organs, namely antheridia and archegonia, respectively.
• The antherozoids produced by the antheridia require water for their transport to the mouth of the archegonium.
• Fusion of the antherozoids- male gamete with the egg in the archegonium results in the formation of the zygote.
• Zygote then develops into a multicellular and well-differentiated sporophyte.

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 liverwort and zygote of a fern.

Answer –

• Protonemal cell of a moss – Haploid
• 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

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

Answer –

ECONOMIC IMPORTANCE OF ALGAE –

• A half of the total carbon dioxide fixation on earth is carried out by algae through photosynthesis.
• Primary producers of energy-rich compounds.
• Many marine algae-like Porphyra, Laminaria, and Sargassum are used as food.
• Marine brown and red algae produce large amounts of hydrocolloids like algin and carrageen, respectively. These are used commercially.
• Agar used to make ice creams and jellies and to grow microbes is obtained from algae Gelidium and Gracilaria.
• Unicellular algae like Chlorella and Spirulina are rich in protein and used as supplements by space travellers.

ECONOMIC IMPORTANCE OF GYMNOSPERMS –

• These can be used as ornamentals and in landscaping for example- Bonsai.
• The fibres of gymnosperms can be used for the production of paper pulp.
• Many useful oils are extracted from gymnosperms.
• Occasionally they can be used in silk production.

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

Answer – The reason why gymnosperms and angiosperms, although bearing seeds, are classified separately is that –

• Ovules are found naked in gymnosperms while ovule is enclosed within the ovary in angiosperms.
• Double fertilization is absent in gymnosperms while it is a significant process in angiosperms.
• While gymnosperms lack vessels in their xylem, the presence of xylem vessels is a characteristic feature of angiosperms.
• Endosperm is haploid and produced prior to fertilization in gymnosperms while the endosperm is triploid and produced after double fertilization in angiosperm.

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

Answer – Heterospory is the phenomenon of producing two different kinds of spores by the sporophyte of the same plant. The following are the significance of the heterospory –

• Heteropory stimulates seed development in gymnosperms and angiosperms.
• This is important to distinguish between male and female gametophytes.

Examples – Salvinia and Selaginella.

8. Explain briefly the following terms with suitable examples.

(i) protonema
(ii) antheridium
(iii) archegonium
(iv) diplontic
(v) sporophyll
(vi) isogamy

Answer –

• (i) Protonema – It is the first stage of the gametophyte. It develops from spores. It is a creeping, green and filamentous stage. Example – in mosses.
• (ii) Antheridium – It is the male sex organ in the plants of bryophytes and pteridophytes which produces male sex gametes called antherozoids.
• (iii) Archegonium – The female sex organ in the plants of bryophytes and pteridophytes which produces female sex gametes called eggs.
• (iv) Diplontic – The stage in the life cycle which is diploid and produces haploid gametes. Ex- In pteridophytes, sporophyte is diplontic.
• (v) Sporophyll – Sporophyll is a leaf which bears sporangia which produce spores. It may be microsporophyll and megasporophyll. In some cases, they may form a compound structure called strobili or cones. Example- Selaginella
• (vi) Isogamy – Reproduction in which gametes are flagellated but similar in size or non-flagellated but similar in size. The fusion of such gametes is called Isogamy. Example- Spirogyra and Chlamydomonas.

9. Differentiate between the following –

(i) red algae and brown algae
(ii) liverworts and moss
(iii) homosporous and heterosporous pteridophyte
(iv) syngamy and triple fusion

Answer –

(i) Red algae and Brown algae

RED ALGAE	BROWN ALGAE
The major pigments are chlorophyll a and b.	The major pigments are chlorophyll a, c and fucoxanthin.
The stored food is starch.	The stored food is mannitol and laminarin.
Example- Porphyra, Gelidium	Example- Laminaria, Fucus

(ii) Liverworts and Moss

LIVERWORTS	MOSS
There exists no protonema stage in liverworts.	There is the first stage of the gametophyte called protonema
Thallus is dorsiventral and closely appeased to substrate.	The plant body is divided into the stem axis.
Example- Marchantia	Example- Funaria

(iii) homosporous and heterosporous pteridophyte

HOMOSPOROUS PTERIDOPHYTE	HETEROSPOROUS PTERIDOPHYTE
In these plants, all spores are of a similar kind.	In these plants, they produce two kinds of spores, macro (large) and micro (small) spores.
Example- Equisetum	Example- Salvinia

(iv) syngamy and triple fusion

SYNGAMY	TRIPLE FUSION
Fusion of male gamete and a single egg are called syngamy.	Fusion of another male gamete and two polar nuclei.

10. How would you distinguish monocots from dicots?

Answer –

MONOCOTS	DICOTS
They have a single cotyledon seed.	They have two seed cotyledons.
Tap roots are found.	Fibrous and adventitious roots are found.
Scattered vascular bundles.	Vascular bundles are found organized in a ring manner.
Leaves venation is parallel.	Leaves venation is reticulate.
Vascular cambium is absent.	Vascular cambium is present.

11. 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 –

COLUMN I	COLUMN II
(a) Chlamydomonas	(iii) Algae
(b) Cycas	(iv) Gymnosperm
(c) Selaginella	(ii) Pteridophyte
(d) Sphagnum	(i) Moss

12. Describe the important characteristics of gymnosperm.

Answer – Following are the characteristics of gymnosperms –

• In gymnosperm, ovules are not enclosed by the ovary, before and after fertilization.
• Gymnosperms seeds are naked.
• The gymnosperms have a diplontic life cycle.
• Generally, tap roots are present.
• Both unbranched (Cycas) and branched (Pinus, Cedrus) stems are present.
• The needle-like leaves in conifers reduce surface area to reduce water loss. Their thick cuticle and sunken stomata also help.
• Gymnosperms leaves are able to withstand harsh climates.
• They are heterosporous.