NCERT Exemplar for Class 11 Biology Chapter-3 (Book Solutions)

Multiple Choice Questions (MCQs)

1. Cyanobacteria are classified under

(a) Protista

(b) Plantae

(c) Monera

(d) Algae

Ans: (c) Monera

2. Fusion of two motile gametes which are dissimilar in size is termed as

(a) Oogamy

(b) Isogamy

(c) Anisogamy

(d) Zoogamy

Ans: (c) Anisogamy

Explanation: Because the size of the gametes differs, the term ‘Anisogamy’ is employed.

3. Holdfast, stipe and frond constitutes the plant body in case of

(a) Rhodophyceae

(b) Chlorophyceae

(c) Phaeophyceae

(d) All of the above

Ans: (c) Phaeophyceae

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

Ans: (d) Bryophytes

Explanation: Monocot and gymnosperm plants do not require water for fertilisation. Water is required for the fertilisation of bryophytes and pteridophytes. Pteridophytes, on the other hand, have actual roots. As a result, ‘d’ is the right answer.

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

Ans: (c) A gametophyte free-living structure formed in pteridophytes

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

Ans: (d) Gymnosperms

Explanation: Gymnosperms are known for their cones. Gymnosperms are also well-adapted to harsh environments.

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

Ans: (b) 7 cells and 8 nuclei

Explanation: One egg cell, two synergids, three antipodal cells, and one secondary nucleus make up the seven cells. The secondary nucleus has two nuclei, whereas each of the other cells has one nucleus

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

Ans: (c) 54

Explanation: After a haploid male gamete and a diploid secondary nucleus fuse, the endosperm is generated. Thus, the endosperm is a triploid nucleus; which will have three times the number of chromosomes as in a haploid nucleus.

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

Ans: (a) Haploid and is found in mosses

10. The giant Redwood tree (Sequoia sempervirens) is a/an

(a) Angiosperm

(b) Free fern

(c) Pteridophyte

(d) Gymnosperm

Ans: (d) Gymnosperm

Explanation: Redwood trees are a Gymnosperm with several nicknames, including tallest tree, oldest tree, and largest by the trunk.

Very Short Answer Questions

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

Ans: In Phaeophyceae, or Brown Algae, mannitol is the reserve food resource.

2. Give an example of plants with

(a) Haplontic life cycle

Ans: Volvox, Spirogyra

(b) Diplontic life cycle

Ans: Fucus

(c) Haplo- diplontic life cycle 

Ans: Polysiphonia

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?

Ans: Rhizome

4. Most algal genera show haplontic lifestyle. Name an alga which is

(a) Haplo-diplontic

Ans: Ectocarpus, Polysiphonia

(b) Diplontic

Ans: Fucus

5. In Bryophytes male and female sex organs are called______and_______.  

Ans: Antheridium, Archegonium

Short Answer Questions

1. Why are bryophytes called the amphibians of the plant kingdom?

Ans: Bryophytes, like amphibians, require water for at least one stage of their life cycle, including the laying of eggs and the development of tadpoles. As a result, bryophytes are known as the plant kingdom's amphibians.

2. Several pteridophytes and gymnosperms have male and female reproductive organs that are similar to angiosperm floral structures. Compare and contrast the reproductive portions of pteridophytes and gymnosperms with angiosperm reproductive systems.

Ans:

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 the plant kingdom?

Ans: The development of two kinds of spores is referred to as heterospory. Megaspores are substantially bigger than microspores. Microspores and megaspores germinate in various Pteridophytes, resulting in male and female gametophytes. The zygote develops within the female gametophyte at the end of the process. This is a forerunner of seed habit in higher plants, according to evolutionary theory. Gymnosperms and angiosperms have been able to survive lengthy periods of adverse weather thanks to seeds. Seed distribution has also allowed them to proliferate across a larger geographic region. It has unquestionably aided the development of these plants.

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

Ans: In the case of Selaginella, the zygote develops into an embryo within the female gametophyte. This female gametophyte is kept on the parent plant for different amounts of time. Because higher plants, such as gymnosperms and angiosperms, exhibit a more evolved version of this phenomena, it's thought to be a forerunner to seed habit. However, unlike seeds in higher plants, Selaginella embryos must grow swiftly in order to start a new generation. However, there may be a brief halt to embryo development, analogous to seed dormancy in higher plants.

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 the ‘relic of the past’. Can you establish a phylogenetic relationship of Cycas with any other group of plants that justifies the above statement?

Ans: Because Cycas is the only surviving species in the Cycadaceae family, it is called a living fossil. All additional members of this family have died out. This plant is sometimes referred to as a plant of the Old World since it can only be found in locations that are linked with some of the world's oldest rocks. For these reasons, it is regarded as a "relic of the past."Furthermore, Cycas resembles Pteridophytes more than Gymnosperms. The evolutionary connection between Pteridophytes and Gymnosperms is shown in this diagram. The following are some of Cycas' characters that point in this direction:

1. When the embryo is still developed, the seeds are shed. Seeds are shed only after the embryo is developed in other gymnosperms.

2. The megasporophyllus has the appearance of a leaf.

3. Male gametes are flagellate despite the presence of pollen tubes. 

4. The base of the leaf remains determined.

5. Circinate the ptysix, which is a kind of ptysix.

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

Ans: In pteridophytes, heterospory results in the formation of two types of spores: microspores and megaspores. This is analogous to how male gametes are substantially smaller than female gametes in higher plants. Another noteworthy trait is embryo growth in situ, which is analogous to embryo development in higher plants. The embryo's development inside the female gametophyte allows it to feed on the female gametophyte. This is beneficial for the normal growth of the embryo as well as ensuring the embryo's survival. As a result, heterospory in pteridophytes might be considered a forerunner to seed habit in gymnosperms.

7. Comment on the lifecycle and nature of a fern prothallus.

Ans: Pteridophytes (ferns) have a haplo-diplontic state. Both the gametophytic and sporophytic stages are multicellular in this situation. A dominant, autonomous, photosynthetic, vascular plant body represents the diploid sporophyte. The haploid gametophyte is likewise self-contained, although it has a shorter life span than the sporophyte generation. The life cycle of a plant with a haplo-diplontic condition is depicted in the diagram below.

The haploid gametophyte generation is represented by the prothallus in ferns. It is a multicellular, self-contained photosynthetic organism with a brief life span. The prothallus requires a chilly, wet, and shaded environment to thrive. Pteridophytes are confined to specific geographical areas due to their need for water for fertilization.

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

Ans: The difference between male gametophyte of pteridophytes  and male gametophyte of gymnosperm are as follows:

The difference between female gametophyte of pteridophyte and gymnosperm are as follows:

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

Ans: Mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant. Mycorrhiza is found in some gymnosperm genera, such as Pinus.

Coralloid Roots: These roots, too, have a symbiotic relationship, but this time with nitrogen-fixing cyanobacteria. Many nodules are formed in the roots giving them coralloid appearance. Examples are Cycas and plants of Leguminosae.

Long Answer Questions

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

Ans: Alternation in a generation may be seen in bryophytes, with both gametophytic (haploid) and sporophytic (diploid) generations occurring. Gametophytic plants, on the other hand, indicate the dominating phase. The thalloid phase of the gametophyte is autonomous, photosynthetic, and independent. The gametophyte produces antheridia and archegonia. These organs are made up of many cells. These organs contain the male and female gametes, respectively. Biflagellate antherozoids are produced by the antheridium. The archegonium has the form of a flask. It only produces one egg. Water is used to transport antherozoids to the archegonium. The mobility of the antherozoids is aided by flagella. After fertilisation, a zygote is created. However, the zygote does not go through meiosis right after fertilisation. It grows into a sporophyte, which is a multicellular organism. In bryophytes, the sporophyte is significantly smaller and is linked to the gametophyte rather than being autonomous. The gametophyte provides it with food. In every way, the gametophyte is the most important phase in a bryophyte's life cycle. The gametophyte is a self-contained, photosynthetic organism. In comparison to the sporophyte, it is significantly bigger. The sporophyte, on the other hand, is not free-living and must remain linked to the gametophyte in order to obtain sustenance.

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

Ans: The haplo-diplontic life cycle is seen in both pteridophytes and bryophytes. In bryophytes, the diploid phase is not independent, but in pteridophytes, it is. Furthermore, in pteridophytes, the sporophyte is more visible than in bryophytes. The major phase of the pteridophyte's life cycle is sporophyte. The given figure shows the haplo-diplontic life cycle.

Sporophyte: A sporophyte is a mature plant body. True roots, stems, and leaves are the three types of roots. In certain regions of the plant, the vascular tissue is well developed. The sporangia are carried by the sporophyte. Sporophylls are leaf-like appendages that protect Sporangia.

Spore Formation: To create spores, the spore mother cells in the sporangia undergo reduction division.

Spore Germination: Spores germinate to form the gametophyte. A gametophyte is a tiny, multicellular organism. It is a free-living, photosynthetic organism. It's known as prothallus. It has male and female gametes in the form of antheridia and archegonia. The male gamete is transferred through the pollen tube, and then fertilisation occurs.

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 independently from each other.

(b) Both will die

(c) Algal components will survive while the fungal component will die.

(d) Fungal components will survive while the algal partner will die. Based on your answer, how do you justify this association as symbiosis? 

Ans: Option ‘b’ is the proper choice, as both of them will perish.

Symbiosis: This is a symbiotic interaction that may be defined as a partnership between two or more organisms. Two creatures that benefit from each other's presence. There are a lot of examples of symbiotic relationships in which the death of one partner does not necessarily result in the death of the other. In a symbiotic relationship between a bird and a buffalo, for example, the bird's only food source is not the worms and insects on the buffalo's back. Similarly, the buffalo may be able to get rid of the pests in various ways. In the case of lichen, however, both the fungal and algal components rely on one other for survival. Alga is the only food source for the fungal component in this example. Similarly, the algae's only source of water and nutrients is a fungus. They have no other way to meet their needs, so if one spouse dies, the other will perish. It will still be termed symbiosis since it is a mutually beneficial connection.

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

Ans: One of the male gametes in angiosperms combines with the female gamete. A second male gamete also unites with the secondary nucleus. Fusion between male and female gametes results in the formation of the zygote. Apart from that, the fusion between another male gamete and the secondary nucleus results in formation of the primary endosperm nucleus (PEN). Since two instances of fusion of nuclei take place hence it is called double fertilization. Two following figure shows double fertilization:

5. Draw labelled diagrams of

(a) Female and male thallus of a liverwort.

Ans: Liverwort

(b) Gametophyte and Sporophyte of Funaria.

Ans: Funaria, Gametophyte and sporophyte

(c) Alternation of Generation in Angiosperm.

Ans: Alternation of generation in Angiosperm

NCERT Exemplar for Class 11 Biology

Students can download the unsolved NCERT Exemplar for Class 11 biology book from the official site of the National Centre of Education and Research Training (NCERT) and also Vedantu. To download the solutions of the example, click on the link on this page. Vedantu teacher offers solutions in a detailed manner. It helps you understand the concepts more clearly.

Chapter 3 of Biology Class 11

The Third chapter of the class 11 NCERT book talks about the plant kingdom. In this chapter, you read about the Plantae under Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms, and their classifications.

Main Terms in the Plant kingdom

1. Numerical Taxonomy is a classification system in biology, which is used to group similar character states.

2. Cytotaxonomy is based on cytological information like chromosome number, structure.

3. Chemotaxonomy uses chemical constituents of the plants.

Benefits of Solved NCERT Exemplar Class 11 Biology- Plant kingdom

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