3 NCERT Class 11 Chapter 3 – Plant Kingdom

 

Answers to Biology NCERT Class 11 Chapter 3 – Plant Kingdom

1. What is the basis for classification of algae?

Solution:

The presence of pigments that give the traditional colour on algae is the main basis for the classification of algae.

Name of the pigment	Colour imparted	Chlorophyll type
Chlorophyceae	Green	chlorophyll a and chlorophyll b
Phaeophyceae	Brown	chlorophyll a, chlorophyll c, fuxoxanthin
Rhodophyceae	Red	chlorophyll a and chlorophyll d, phycoerythrin

Now, algae are classified on different criteria such as:

(i) Flagellation

(ii) Storage products

(iii) Cellular organization

(iv) Constitution of cell walls

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

Solution:

The reduction division takes place in the following stages:

(i) Liverworts – meiosis takes place in the spore mother cells of the capsule in sporangium resulting in haploid spore formation

(ii) Moss – meiosis occurs in spore mother cells of spore sacs in the capsule of sporangium.

(iii) Fern – sporangia are endured on sporophylls (fertile leaves). The process of meiosis occurs in spore mother cells of sporangium for the formation of haploid spores.

(iv) Gymnosperm – meiosis occurs in microsporangia located in the microsporophylls, in the microspore mother cells for the formation of haploid pollen grains giving rise to male gametophyte

(iv) Angiosperm – pollen grains that are formed in microspore mother cells leads to the formation of male gametophyte in the anther of the stamen. The megaspore mother cell located in the nucleus of the ovule undergoes meiosis for the formation of haploid megaspore, which eventually forms the female gametophyte.

3. Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.

Solution:

Bryophytes, Pteridophytes, and Gymnosperms are the plants that bear archegonia.

The life cycle of Bryophytes

(i) Bryophytes are haploid, and produce gametes. The sexual organs in bryophytes are multicellular.

(ii) The male sex organ is the antheridium, which produces biflagellate anterozoids. Female sexual organs are called archegonium, which produces a single egg.

(iii) Antheridium releases anthrozoids into the water that come in contact with the archegonium.

(iv) An antherozoid fuses with the egg to produce the zygote.

(v) The zygote undergoes reduction division to produce a multicellular body called a sporophyte.

(vi) Sporophytes undergo reduction division to produce haploid spores.

(vii) These spores germinate to produce gametophyte.

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 a liverwort, and zygote of a fern.

Solution:

Cell	Type of Ploidy
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.

Solution:

Importance of Gymnosperms

(i) Gymnosperms are used as ornamental plants. Some are features in formal gardens – used for bonsai

(ii) Their fibers are used in the preparation of paper pulp

(iii) Turpentine and resins are obtained from confers resin

(iv) Useful oils are extracted from gymnosperms like junipers, pines, hemlock, fir, spruces, and arborvitae

(v) Gymnosperm seeds are used as food products such as bakery items

(vi) Occasionaly used to create silk and other textiles

Importance of Algae

(i) Algae fixes carbon dioxide with the help of photosynthesis

(ii) It increases the level of dissolved oxygen in their immediate environment

(iii) They produce rich compounds that serve as food for aquatic animals

(iv) Marine algae are used as food. For example, Laminaria and Sargassum

(v) Certain algae are used as hydrocolloids

(vi) Agar is used in growing microorganisms and in the preparation of jellies

(vii) Chlorella is used as food by space travellers.

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

Solution:

The reasons for distinguishing angiosperms and gymnosperms are as follows.

(i) In gymnosperms, the ovules are naked but in angiosperms they are enclosed within the ovary.

(ii) In Gymnosperms endospore is haploid and produced before fertilization whereas in Angiosperms endosperm is triploid and formed after double fertilization.

(iii) Double fertilization does not occur in gymnosperms, but in angiosperms, double fertilization occurs.

(iv) In gymnosperms, wood is nonporous and in angiosperms wood is porous.

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

Solution:

The phenomenon of producing two different types of spores in the same plant is called heterosporis. The importance of heterospory is as follows:

(i) Heterosporis causes the growth of seeds in gymnosperms and angiosperms.

(ii) It is required in the differentiation of male and female gametophytes.

Examples: Salvinia, Selaginella

8. Explain briefly the following terms with suitable examples:

(i) protonema

(ii) antheridium

(iii) archegonium

(iv) diplontic

(v) sporophyll

(vi) isogamy

Solution:

i) Protonema is the haploid stage in the bryophyte lifecycle where thread-like chain of cells are formed. For example, in mosses, protonema develops directly from a spore.

ii) Antheridium – The male sex organ, producing male gametes in bryophyte and pteridophytes is called antheridium. For example, many fungi and algae have antheridia during their reproductive phases.

iii) Archegonium is a female reproductive organ of bryophytes which is flask-shaped and produces a single egg. Observed in pteridiophytes, gymnosperms and bryophytes, they are jacketed and multicellular, possessing a neck and a swollen venter.

iv) Diplontic – A life cycle in which dominant free living phase is diploid, generating haploid gametes. For example, Sargassum.

v) A leaf which bears sporangia is called a sporophyll, which may be microsporophyll or megasporophyll. These structures combine to form strobini(cones). For example, Pinus.

vi) Isogamy – Sexual reproduction that takes place through fusion of two gametes which can be flagellated and are similar in size, or non-flagellated (non-motile) but similar in size. Such reproduction is called isogamy. For example, Ectocarpus

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

Solution:

Following are the differences:

i)

1. Red algae contain chlorophyll a and chlorophyll d but brown algae contain chlorophyll a and c.

2. In red algae, Phycobilins are present but brown algae do not have phycobilins.

3. If red algae reserve food in the form of floridian starch, it is laminarin in brown algae.

4. Red algae are not flagellated, and brown algae are flagellated.

ii)

1. There is no protonema phase in the liverworts and the life cycle in the moss begins with the protonema

2. If the plant body is dorsoventral in liverworts, the algal plant body is separated into a stem-axis.

iii) Homosporous possesses only one type of spores whereas heterosporous will have morphologically different spores in different sporangia.

iv) Syngamy is the fusion of the male gamete with the ovum whereas triple fusion is the fusion of another male gamete with two polar nuclei.

10. How would you distinguish monocots from dicots?

Solution:

Monocots	Dicots
Have single cotyledon seed	Seeds having two cotyledons
Flowers are trimerous	Flowers are tetramerous or pentamerous
Venation in leaves is parallel	Have reticulate venations in leaves
Vascular bundle is scattered	Vascular bundle are organised in a ring
Absence of vascular cambium	Presence of vascular cambium
Primary root replaced by adventitious roots and are short-lived	Primary roots occur in a few cases. Primary root is long-lived

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

Solution:

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 gymnosperms.

Solution:

The main characteristics of gymnosperms are as follows:

(i) In Gymnosperm the ovules are not enclosed by ovary. They are exposed before and after fertilization

(ii) The seeds are naked

(iii) Gymnosperms include medium-sized trees or tall trees and shrubs

(iv) The roots are taproots

(v) The stems are branched or unbranched

(vi) Leaves are simple and compound

(vii) The plant body is separated into roots, stems and leaves and is sporophyte

(viii) They produce two kinds of spores, so they are called heterosporous

(ix) Fertilization takes place in the absence of external water from syphonogamy

2 NCERT Class 11 Chapter 2 – Biological Classification

 

Access Answers of Biology NCERT Class 11 Chapter 2 – Biological Classification

1. Discuss how classification systems have undergone several changes over a period of time.

Solution:

Aristotle was the first to introduce scientific classification. He used simple morphological characters to classify plants into trees, shrubs, and herbs. He divided the animals into two groups, one with red blood and one without.

Linnaeus introduced a two-kingdom classification, which includes Plantae and Animalia, respectively, of plants and animals. But this classification does not classify eukaryotes and prokaryotes, single-celled and multicellular organisms, photosynthetic (green algae) and non-photosynthetic (fungal) organisms. Therefore, the system was found to be less significant as it did not include more features.

Thus, the classification of living organisms has undergone several changes. R.H. Whittaker introduced a five-kingdom classification, including Monera, Protista, Fungi, Plantae and Animalia. Some of the characteristics included in this classification are the structure of cells, body organisation, mode of nutrition, mode of reproduction, and phylogenetic relationship to classify organisms. Subsequently, a three-domain system was proposed, which divided Kingdom Monera into two domains, leaving the remaining eukaryotic kingdoms in the third domain, thereby classifying the six kingdoms.

2. State two economically important uses of:

(a) heterotrophic bacteria

(b) archaebacteria

Solution:

a) Heterotrophic bacteria are used in the production of vitamins, antibiotics, cheese and curd.

They help fix nitrogen and are used in the formation of humus.

b) Archaebacteria are used in Biogas production.

They are used in the bioleaching of mines.

3. What is the nature of cell walls in diatoms?

Solution:

In diatoms, cell walls are embedded with silica imparting characteristic patterns onto the walls and are indestructible. These diatoms leave large amounts of cell wall deposits in their habitat to accumulate to form the diatomaceous earth.

4. Find out what the terms ‘algal bloom’ and ‘red tides’ signify.

Solution:

Algal blooms are found in contaminated water. They are an overgrowth of algae, especially blue-green algae (cyanobacteria). Their growth leads to water pollution. They inhale carbon dioxide and exhale oxygen.

Rapid multiplication of red-pigmented dinoflagellates, such as Gonaulax, gives the sea a red colour, a phenomenon known as red tides. These algae produce toxins that kill fish and other aquatic organisms.

5. How are viroids different from viruses?

Solution:

(i) Viroids are small infectious agents with single-stranded RNA without a protein coat, but viruses have single-stranded or double-stranded RNA bound with a protein coat.

(ii) Viroids are very small in size compared to viruses.

(iii) Viroids infect only plants, while viruses infect plants, animals, and microorganisms.

6. Describe the four major groups of Protozoa briefly.

Solution:

Four major groups of Protozoa are as follows:

Amoeboid protozoans: Found in the aquatic environment, they move and catch their prey using pseudopodia.

Flagellated protozoans: These protozoans are free-living or parasitic. Their locomotory structure is flagella.

Ciliated protozoans: They live in aquatic environments, and the presence of cilia makes them actively moving.

Sporozoans: They contain a wide variety of organisms, producing infectious spores throughout their life cycle. Their spore-like phase helps them move from one host to another.

7. Plants are autotrophic. Can you think of some plants that are partially heterotrophic?

Solution:

Insectivores and carnivorous plants are partially heterotrophic; these organisms are green and autotrophic, but they prey on and digest small components for their nitrogen supply.

Ex; Utricularia, Drosera, Nepenthes.

8. What do the terms phycobiont and mycobiont signify?

Solution:

Lichens are a symbiotic association of fungi and algae. Phycobiont is part of algae and part of mycobiont fungi. Mycobiont provides structural cover that protects the algae from unfavourable conditions. Similarly, phycobionts prepare food through the process of photosynthesis, which is used by both organisms.

9. Give a comparative account of the classes of Kingdom Fungi under the following:

(i) mode of nutrition (ii) mode of reproduction

Solution:

	Phycomycetes	Ascomycetes	Basidiomycetes	Deuteromycetes
Mode of nutrition	Saprophytic or parasitic	Decomposers, Saprophytic or parasitic or coprophilous	Saprophytic	Decomposers, Saprophytic or parasitic
Mode of reproduction	Asexual reproduction by zoospore (motile) and Aplanospore (non-motile) Sexual reproduction – zygote can be similar or dissimilar in morphology	Through asexual spores called conidia, and sexual spores are known as ascospores	By vegetation reproduction through budding. The fusion of two somatic cells for the formation of basidiospores is Plasmogamy	Through asexual spores called conidia.

10. What are the characteristic features of Euglenoids?

Solution:

The typical features of Eugenoids are:

(i) Absence of cell wall.

(ii) Their body is flexible because there is a protein-rich layer called a pellicle.

(iii) Two flagella of different lengths are found.

(iv) They are autotrophic in the presence of sunlight and heterotrophic in the absence of sunlight.

11. Give a brief account of viruses with respect to their structure and nature of genetic material. Also, name four common viral diseases.

Solution:

Viruses are infectious agents that crystallise in structure when found outside the host cell. The genetic material is either DNA or RNA (never both), and they are located within the protein core. If the virus that infects plants has single-stranded RNA, then the viruses that infect animals are single or double-stranded DNA or RNA. The capsid is their protein coat, which in turn is made up of small subunits called capsomers, which protect nucleic acid.

Common viral diseases are Influenza, AIDS, Herpes and Rabies.

12. Organise a discussion in your class on the topic ‘Are viruses living or nonliving’?

Solution:

Non-living Characters

(i) No cellular structure

(ii) They can be stored in bottles like crystals

(iii) There will be no energy storage or energy liberation systems

(iv) They cannot grow or multiply outside the host

Living Characters

(i) They are host-specific

(ii) The presence of genetic material

(iii) The ability to multiply

(iv) They have antigenic properties

(v) They are obligate parasites

(vi) Mutations occur

List of subtopics covered in Chapter 2 – Biological Classification

Number	Subtopic
2.1	Kingdom Monera
2.2	Kingdom Protista
2.3	Kingdom Fungi
2.4	Kingdom Plantae
2.5	Viruses, Viroids, Prions And Lichens

1 Reproduction in organism

 

1 Answers to NCERT Class 11 Biology Chapter 1 – The Access Living World

Answers to NCERT Class 11 Biology Chapter 1 – The Access Living World

1. Why are living organisms classified?

Solution:

The earth contains millions of organisms, and we may know the plants and animals that live near us by their native names. The local names vary from place to place within a country. This leads to confusion in identifying and studying specific species. Therefore, it must be called by a common name throughout the world to standardise the nomenclature and study of organisms. To achieve this, organisms are named and categorised according to their roles.

2. Why are the classification systems changing every now and then?

Solution:

Scientific study is ever a work in progress, and new species and organisms are often added. The initial system of classification focuses only on the habits and habitat of organisms. Gradually, external morphology became a tool for classification. After this, the morphology and embryology are taken into account, followed by the phylogenetic relationship and the cytology of the organism. Modern-day uses biochemical techniques to classify organisms based on their nucleic acid components.

3. What different criteria would you choose to classify people that you meet often?

Solution:

The people we meet most often are categorized by characteristics such as gender, skin colour, education, career, hobbies, and nature.

4. What do we learn from the identification of individuals and populations?

Solution:

By identifying individuals and populations, we learn the following things:

(i) Sex

(ii) Skin colour

(iii) Native place

(iv) Mother tongue

(v) Food habit

(vi) Religion

(vii) Caste

5. Given below is the scientific name of Mango. Identify the correctly written name.

Mangifera Indica

Mangifera indica

Solution:

The answer is Mangifera indica. Here, Mangifera is its genus name, and indica is its species name which is always written in lowercase.

6. Define a taxon. Give some examples of taxa at different hierarchical levels.

Solution:

A taxon is a level of hierarchy in the system of classifying organisms.

Following are the hierarchical levels:

(i) Kingdom

(ii) Phylum

(iii) Class

(iv) Order

(v) Family

(vi) Genus

(vii) Species

7. Can you identify the correct sequence of taxonomical categories?

(a) Species Order Phylum Kingdom

(b) Genus Species Order Kingdom

(c) Species Genus Order Phylum

Solution:

From the given options, (a) and (c) is the correct sequence of taxonomical categories.

8. Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in the case of higher plants and animals on the one hand and bacteria on the other hand.

Solution:

A group of individual organisms with basic similarities is called species. This is the basic unit of classification. Species are defined as individuals who share the same gene pool.

Higher plants and animals: Criteria of reproductive isolation can be used to classify the species.

Bacteria: Interbreeding and reproductive isolation cannot be used in the case of bacteria; here, a gene pool can be used to classify species.

9. Define and understand the following terms.

(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus

Solution:

i) Phylum is a taxonomical hierarchy below Kingdom and above Class. It is a taxon with one or more classes of organisms with similar characteristics.

ii) Class is a taxonomical hierarchy higher than Order and lower than Phylum. Class includes related to orders of the organisms. Example: Presence of notochord in mammals.

iii) Family has a group of related genera with still less number of similarities as compared to genus and species. Example: Fox and dog belongs to the same family. It is a group of entities below Order and above Genus.

iv) Order is a taxon below higher than Family and lower than class. Order being a higher category, is the assemblage of families which exhibit a few similar characters.

v) Genus comprises a group of related species which has more characteristics in common in comparison to species of other genera. Examples: Lion, tiger and leopard are classified under the genus Panthera. It is above species and below the family.

10. How is a key helpful in the identification and classification of an organism?

Solution:

The key is a taxonomic aid used to identify plants and animals based on similarities and dissimilarities. It represents the choice between two opposite characters. This is useful for identifying contrasting characters. They are two contrasting characters, where one character’s choice rejects another when the species, family, or genera is identified.

If the entity is not already recorded, efforts are made for the first verification and reconsider its discovery before naming it. Therefore, each entity can be classified as it is known or unknown.

11. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

Solution:

The table below depicts the taxonomic hierarchy with wheat as an example of a plant and humans as an example of an animal.

Taxonomic categories	Wheat	Human
Kingdom	Plantae	Animalia
Phylum/Division	Angiospermae	Chordata
Class	Monocotylydonae	Mammalia
Order	Poales	Primata
Family	Poaceae	Homonidae
Genus	Triticum	Homo
Species	aestivum	Sapiens