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NCERT Solutions for Class 11 Science Biology Chapter 3 Plant Kingdom are provided here with simple step-by-step explanations. These solutions for Plant Kingdom are extremely popular among Class 11 Science students for Biology Plant Kingdom Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the NCERT Book of Class 11 Science Biology Chapter 3 are provided here for you for free. You will also love the ad-free experience on Meritnation’s NCERT Solutions. All NCERT Solutions for class Class 11 Science Biology are prepared by experts and are 100% accurate.

Page No 10:

Question 1:

Cyanobacteria are classified under
a. Protista
b. Plantae
c. Monera
d. Algae

Answer:

Cyanobacteria or blue-green algae are photosynthetic, gram-negative eubacteria and thus belong to the kingdom Monera.

Hence, the correct answer is option c.

Page No 10:

Question 2:

Fusion of two motile gametes which are dissimilar in size is termed as
a. Oogamy
b. Isogamy
c. Anisogamy
d. Zoogamy

Answer:

Oogamy involves the fusion of the male gamete with the female ovum. The fusion of two gametes that are difficult to differentiate is termed Isogamy. The fusion of two motile gametes which are dissimilar in size or appearance is termed Anisogamy and sexual reproduction of animals is termed zoogamy.

Hence, the correct answer is option c.

Page No 10:

Question 3:

Holdfast, stipe and frond constitutes the plant body in case of
a. Rhodophyceae
b. Chlorophyceae
c. Phaeophyceae
d. All of the above

Answer:

Rhodophyceae, commonly known as red algae have a multicellular thalloid body with complex body organization in some cases. Where else,  Chlorophyceae or green algae are unicellular, colonial, or filamentous and thus do not possess differentiated thallus. Phaeophyceae or brown algae have well-differentiated thallus consisting of the holdfast, a stalk like a stipe, and a photosynthetic frond.

Hence, the correct answer is option c.

Page No 10:

Question 4:

A plant shows thallus level of organization. It shows rhizoids and is haploid. It needs water to complete its life cycle because the male gametes are motile. Identify the group to which it belongs to
a. Pteridophytes
b. Gymnosperms
c. Monocots
d. Bryophytes

Answer:

Bryophytes are multicellular, cryptogamous, haplo-diplontic (with predominant gametophytic phase), amphibious plants requiring water for transfer of antherozoids from antheridium to archegonium and have thallus level of organization. Bryophytes lack true vegetative structures of vascular plants but possess root-like rhizoids to hold on to substratum and draw water and dissolved minerals from it.

Hence, the correct answer is option d.

Page No 10:

Question 5:

A Prothallus is
a. A structure in pteridophytes formed before the thallus develops
b. A sporophytic free living structure formed in pteridophytes
c. A gametophyte free living structure formed in pteridophytes
d. A primitive structure formed after fertilization in pteridophytes

Answer:

Prothallus is primarily the reduced, photosynthetic, thalloid, free-living gametophytic stage in most of the pteridophytes. Here also water is essential for sexual reproduction leading to the formation of the sporophytic, dominant phase of pteridophytes, with well-differentiated body and vascular bundle. 

Hence, the correct answer is option c.



Page No 11:

Question 6:

Plants of this group are diploid and well adapted to extreme conditions. They grow bearing sporophylls in compact structures called cones. The group in reference is
a. Monocots
b. Dicots
c. Pteridophytes
d. Gymnosperms

Answer:

Plants with a dominant sporophytic phase include pteridophytes, gymnosperms, and angiosperms. Most of the gymnosperms form dense coniferous forests on cold hilly terrains.

Hence, the correct answer is option d.
 

Page No 11:

Question 7:

The embryo sac of an Angiosperm is made up of
a. 8 cells
b. 7 cells and 8 nuclei
c. 8 nuclei
d. 7 cells and 7 nuclei

Answer:

Megasporogenesis is the process of gametogenesis in the female reproductive organs of angiosperms. One of the haploid megaspores thus formed undergoes three rounds of mitosis without cytokinesis. The 8 nuclei thus formed are eventually redistributed to form a structure called embryo sac, with 7 cells and 8 nuclei where all cells are uninucleated except central cell with two polar nuclei.

Hence, the correct answer is option b. 

Page No 11:

Question 8:

If the diploid number of a flowering plant is 36. What would be the chromosome number in its endosperm
a. 36
b. 18
c. 54
d. 72

Answer:

A plant with a diploid number of chromosomes as 36, will produce haploid nuclei after megasporogenesis as 18. The two nuclei of the central cell of the embryo sac will fuse to form a diploid secondary nucleus, which in turn will fuse with one of the two generative cells to form a triploid endosperm with genetic material equivalent to 54 chromosomes.

Hence, the correct answer is option c.

Page No 11:

Question 9:

Protonema is
a. Haploid and is found in mosses
b. Diploid and is found in liverworts
c. Diploid and is found in pteridophytes
d. Haploid and is found in pteridophytes

Answer:

Liverworts and mosses are bryophytes. In the case of mosses, primary protonema develops from the spore to form lateral and prostate gametophytic structures. This gives rise to erect and vertical secondary leafy protonema from the lateral buds of the primary protonema.

Hence, the correct answer is option a.

Page No 11:

Question 10:

The giant Redwood tree (Sequoia sempervirens) is a/an
a. Angiosperm
b. Free fern
c. Pteridophyte
d. Gymnosperm

Answer:

The Giant Redwood tree belongs to the cypress family of conifers, which are gymnosperms.

Hence, the correct answer is option d.

Page No 11:

Question 1:

Food is stored as Floridean starch in Rhodophyceae. Mannitol is the reserve food material of which group of algae?

Answer:

Food produced or accumulated as a result of photosynthesis is stored in various forms within various types of algae. In Chlorophyceae, it is stored within pyrenoids as protein and starch. In Phaeophyceae, it is stored as complex carbohydrates, in the form of laminarin or mannitol, and in Rhodophyceae commonly as floridean starch. 
 



Page No 12:

Question 2:

Give an example of plants with
a. Haplontic life cycle
b. Diplontic life cycle
c. Haplo- diplontic life cycle

Answer:

a) Haplontic life cycle is primarily observed in algae like Volvox, Spirogyra and some species of Chlamydomonas.
b) Diplontic life cycle is observed in phenarogams i.e. gymnosperms and angiosperms.
c) Haplo-diplontic life cycle is observed in bryophytes and pteridophytes.

Page No 12:

Question 3:

The plant body in higher plants is well differentiated and well developed. Roots are the organs used for the purpose of absorption. What is the equivalent of roots in the less developed lower plants?

Answer:

In the case of unicellular (solitary or colonial) or filamentous multicellular algal forms no specialization of organs is found and thus in the whole-cell surface helps in absorption. In Phaeophyceae, the holdfast is meant for attachment to substratum only and not for absorption. In bryophytes, rhizoids serve the dual function of holding the plant body to the substratum and absorption of water and dissolved nutrients. In pteridophytes, gymnosperms, and angiosperms true roots are present, which serves the dual purpose of holding the plant body to the substratum and absorption of water and dissolved nutrients (just like the rhizoids of bryophytes).

Page No 12:

Question 4:

Most algal genera show haplontic life style. Name an alga which is
a. Haplo-diplontic
b. Diplontic

Answer:

a) Algae with haplo-diplontic life cycle includes species of Polysiphonia (Red algae) and brown algae like Ectocarpus and Laminaria.

b) Algae with diplontic life cycle includes species of Fucus (Brown algae).

Page No 12:

Question 5:

In Bryophytes male and female sex organs are called ____________ and __________.

Answer:

In Bryophytes male and female sex organs occur on the gametophyte only. The male sex organ of bryophytes is termed as antheridium and the female sex organ of bryophytes is termed as archegonium.

Page No 12:

Question 1:

Why are bryophytes called the amphibians of the plant kingdom?

Answer:

Bryophytes are the first evolved plants to move out of water and survive on land, but like amphibians they are dependent on water for sexual reproduction. The male gametes (antherozoids) are released into water and move to the archegonium (female sex organ) for fusion with the egg cell. Thus bryophytes are rightly termed as amphibians of the plant kingdom.

Page No 12:

Question 2:

The male and female reproductive organs of several pteridophytes and gymnosperms are comparable to floral structures of angiosperms. Make an attempt to compare the various reproductive parts of pteridophytes and gymnosperms with reproductive structures of angiosperms.

Answer:

The comparison of reproductive structures of pteridophytes and gymnosperms with that of angiosperms is shown in the table given below:
 

Reproductive Parts of Pteridophytes & Gymnosperms Reproductive Structures of Angiosperms
Strobili/Cone Flower
Microsporophyll Stamen
Megasporophyll Psitil/Carpel
Microsporangium Anther
Megasporangium Ovule

Page No 12:

Question 3:

Heterospory i.e., formation of two types of spores – microspores and megaspores is a characteristic feature in the life cycle of a few members of pteridophytes and all spermatophytes. Do you think heterospory has some evolutionary significance in plant kingdom?

Answer:

Heterospory is a phenomenon where a sporophyte plant body produces two different kinds of haploid spores by meiosis, namely microspores and megaspores. This is seen in case of many pteridophytes. In such cases the microspores develops into male gametophytes and megaspores into female gametophytes. The male gametes thus released by the independent male gametophytes enters the archegonium of the independent female gametophyte and fuses with the female gamete. The zygote thus develops inside the female gametophyte and the developing sporophyte is retained on the female gametophyte for some time. This is the precursor of seed habit (because here the sporophyte develops on the female parent plant). This is really advantageous as this allows the sporophyte to overcome the long unfavourable weather outside and also leads to dispersal of plants to new habitats via seed dispersal.

Page No 12:

Question 4:

How far does Selaginella one of the few living members of lycopodiales (pteridophytes) fall short of seed habit.

Answer:

Selaginella is a pteridophyte and in its case the female gametophyte is retained on the parent sporophyte and does not have an independent existence. Thus, the male gamete fertilizes the female gamete inside the female gametophyte that is retained on the parent sporophyte. This is the precursor of seed habit. But unlike in the case of phenarogams, in Selaginella the embryo growth cannot be arrested for a longer duration as in case of dormant seeds and needs to develop quickly into a plant of next generation. Thus, although signs of seed habits are exhibited by Selaginella, it still falls short of it.

Page No 12:

Question 5:

Each plant or group of plants has some phylogenetic significance in relation to evolution : Cycas, one of the few living members of gymnosperms is called as the ‘relic of past’. Can you establish a phylogenetic relationship of Cycas with any other group of plants that justifies the above statement?

Answer:

Cycas are considered "relics of the past" for the following reasons:

i) They are the only living representatives of the the Family Cycadaceae.
ii) They are generally found in those areas where the geological rocks are oldest.
iii) They are less developed than most of the gymnosperms and are more closely related to pteridophytes in the following ways:

a) Seeds are shed when the embryo is still immature compared to other gymnosperms where the seeds are shed when the embryo is mature.
b) The megasporophyll is very much leaf like in appearance.
c) Inspite of producing a pollen tube, they still carry flagellated male gametes like pteridophytes.
d) Circinate ptyxis is observed in Cycas just like that of many pteridophytes.



Page No 13:

Question 6:

The heterosporous pteridophytes show certain characteristics, which are precursor to the seed habit in gymnosperms. Explain.

Answer:

Heterosporous pteridophytes are those pteridophytes that produce two different kinds of spores: microspores and megaspores. Microspores develop into a multicellular, inconspicuous, thalloid, prostate, independent, male gametophyte. Likewise, megaspores develop into independent female gametophytes. In such cases, the motile male gametes released by the male gametophytes in the water enter the archegonium of the female gametophyte. On fusion or fertilization with the female gamete inside the archegonium, the zygote is formed. The zygote develops and grows on the female gametophyte inside the archegonium. This is similar to the growth of an embryo inside the seed of phanerogams and thus is the precursor of the seed habit.

Page No 13:

Question 7:

Comment on the life-cycle and nature of a fern prothallus.

Answer:

Prothallus in the case of pteridophyte is a small, multicellular, photosynthetic, inconspicuous, prostate, independent gametophyte. It is derived from the germination of haploid spores produced by meiosis within the sporophyte. Sporophytes in the case of pteridophytes are the dominant and independent diploid phase of their life-cycle. Gametophytes are reduced, independent haploid phase of life-cycle. The pteridophytes are thus having a haplo-diplontic life-cycle. 

Page No 13:

Question 8:

How are the male and female gametophytes of pteridophytes and gymnosperms different from each other?

Answer:

Following are the differences between male gametophytes of pteridophytes and gymnosperms:
 
Male Gametophyte of Pteridophytes Male Gametophyte of Gymnosperms
(i) In case of homosporous pteridophytes distinct male gametophyte does not exist. (i) Distinct male gametophytes are found in the case of all gymnosperms. 
(ii) Antheridium is the male sex organ present in male gametophytes. (ii) Antheridium is absent in case of gymnosperms.
(iii) Male gametes are motile and flagellated.  (iii) Male gametes are generally non-motile and also motile in some cases.
(iv) Male gametes reaches the female gamete by floating in water. (iv) Male gametophyte or pollens are carried towards the female gametophyte generally via wind and male gametes reaches the female via pollen tube.

Following are the differences between the female gametophyte of pteridophytes and gymnosperms:
 
Female Gametophyte of Pteridophytes Female Gametophyte of Gymnosperms
(i) In case of homosporous pteridophytes distinct female gametophyte does not exist. (i) Distinct female gametophytes is found in case of all gymnosperms.
(ii) Female gametophyte has generally independent existence.   (ii) Female gametophyte has no independent existence and is dependent on the sporophyte for existence.
(iii) Female gametophyte is not enclosed in the ovule. (iii) Female gametophyte is enclosed in the ovule.

Page No 13:

Question 9:

In which plant will you look for mycorrhiza and corolloid roots? Also explain what these terms mean.

Answer:

Mycorrhiza is a symbiotic and mutualistic beneficial association between the roots of the plants and the fungi. In this symbiotic relationship the plant partner provides a place of lodging and food for the fungal partner. In return, the fungal partner helps the roots of the plants in absorption of water and dissolved mineral nutrients. This kind of association is generally observed in the roots of certain gymnosperms like Pinus.

Corolloid roots are those which are symbiotically associated with the nitrogen fixing cyanobacteria. This symbiotic associatioon leads to nodule formation. These kinds of roots are common in gymnsperms like Cycas and angiosperms of Family Leguminaceae.

Page No 13:

Question 1:

Gametophyte is a dominant phase in the life cycle of a bryophyte. Explain.

Answer:

Bryophytes are more evolved compared to the algae but are still not vascular plants. Their thalloid body is more differentiated than algae but lesser than that of pteridophytes. They do not possess true vegetative structures found in higher plants but have leaf-like, shoot-like and root-like structures. Bryophytes show alternation in generation. The main multicellular plant body in case of bryophyte is gametophytic that is haploid. It is large, visible, photosynthetic and an independent structure that grows on a suitable substratum.The gametophytic plant body of the bryophytes bears male and female sexual organs termed as antheridia and archegonia, respectively. The gametophyte bears the male and female gametes inside the antheridia and archegonia respectively. The male gametes are motile and are carried by water currents to the archegonia, where they enter inside it to fuse with the female gamete. Post-fertilization, the zygote develops within the archegonium and gives rise to the diploid sporophyte. The sporophyte grows on the female gametophyte. It is reduced, non-photosynthetic, and is completely dependent on the photosynthetic gametophyte for its nutritional requirements. Thus the dominant phase of the life cycle in the case of bryophytes is gametophytic phase only. The sporophyte bears a foot, a setae (long, slender, stem like structure) with a capsule. The capsule produces many haploid spores by meiosis which are released outside and germinate on the suitable substratum to produce the next generation of gametophytes. 

Page No 13:

Question 2:

With the help of a schematic diagram describe the haplo-diplontic life cycle pattern of a plant group.

Answer:

Haplo-diplontic life cycle is exhibited by bryophytes and pteridophytes. These plants exhibit alternation of generation i.e. the haploid multicellular gametophyte is followed by a diploid stage termed as sporophyte. The gametophyte stage is responsible for the production of haploid gametes, which fuse to give rise to a sporophyte. The diploid sporophyte again produces haploid spores by meiosis. The haplo-diplontic life cycle of plants can be visualised diagrammatically as shown below:
 

HAPLO-DIPLONTIC LIFE CYCLE

Page No 13:

Question 3:

Lichen is usually cited as an example of ‘symbiosis’ in plants where an algal and a fungal species live together for their mutual benefit. Which of the following will happen if algal and fungal partners are separated from each other?
a. Both will survive and grow normally and independent from each other.
b. Both will die
c. Algal component will survive while the fungal component will die.
d. Fungal component will survive while algal partner will die.

Based on your answer how do you justify this association as symbiosis.

Answer:

If the fungal and algal partners of a lichen are separated from each other, they both will perish and die off.  As both the fungal and algal partners involved in the lichen formation have evolved to take benefit of their partner and will be unable to carry out the function of their symbiotic partner all by themselves. Thus if the fungal partner is separated from its algal partner in the lichen, it will not be able to obtain nourishment by alternate means and thus will die. The same is true for the algal partner in the lichen, in the absence of its fungal partner, it will not be able to obtain water and dissolved nutrients from the substratum shared with it by the fungal partner. Therefore, it is important for fungal and algal partners of a lichen to co-exist in a mutually symbiotic relationship for their survival.

Hence the correct answer is option b.

Page No 13:

Question 4:

Explain why sexual reproduction in angiosperms is said to take place through double fertilization and triple fusion. Also draw a labelled diagram of embryo sac to explain the phenomena.

Answer:

Angiosperms are the only plants to exhibit a unique phenomenon of double fertilization within the plant kingdom.

In case of angiosperm the male gametophyte prodcued within the anthers is termed as the pollen grains. Each pollen grain contains one vegetative or tube cell and two generative cells. Both the generative cells are haploid and are the true male gametes. Tube cell or vegetative cell leads to teh formation of pollen tube on the germination of the pollen grain.

Female gametophyte in case of angiosperm is also called as the embryo sac and is a 7 celled, 8 nuclei structure as shown below:



EMBRYO SAC


It contains a single haploid, female gamete, the egg cell. Embryo sac also has a large central cell with 2 polar nuclei. 

During the event of sexual reproduction in flowering plants or angiosperms, the 2 male gametes are carried down to the embryo sac with teh help of growing pollen tube. The 2 male gametes or the generative cell is then guided into teh embryo sac with the help of filliform apparatus of the synergids. One of the generative cell then fuses with the female gamete or the egg cell in the event termed as syngamy.  This leads to the formation of the zygote, which will later on develop into a growing embryo giving rise to the new plant. The other male gamete continues to move into the embryo sac and it's nucleus fuses with the 2 polar nuclei of the central cell in an event termed as triple fusion. This triple fusion leads to teh formation of Primary Endosperm Cell (PEC), which later on grows and develops by mitosis and acts as a nutritive tissue within the seed for teh developing embryo.

Thus, overall during the event of sexual reproduction in flowering plants or angiosperms there are two events of fertilization and therefore it is termed as double fertilization.

Page No 13:

Question 5:

Draw labelled diagrams of
a. Female and male thallus of a liverwort.
b. Gametophyte and sporophyte of Funaria.
c. Alternation of generation in Angiosperm.

Answer:

a. Shown below are the labelled diagrams of male and female thallus of a liverwort:

b. Shown below are the labelled diagrams of gametophyte and sporophyte of Fuaria:
 
Gametophyte & Sporophyte of Funaria

 
c. Shown below is the labelled diagram of alternation of generation in angiosperms:


Alternation of Generation inAngiosperms



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