Case Study Questions Class 11 Biology Chapter 3 Plant Kingdom
CBSE Class 11 Case Study Questions Biology Plant Kingdom. Important Case Study Questions for Class 11 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Plant Kingdom.
At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.
CBSE Case Study Questions Class 11 Biology Plant Kingdom
CASE 1
The earliest systems of classification used only gross superficial morphological characters such as habit, colour, number and shape of leaves, etc. They were based mainly on vegetative characters or on the androecium structure (system given by Linnaeus). Such systems were artificial; they separated the closely related species since they were based on a few characteristics. Also, the artificial systems gave equal weightage to vegetative and sexual characteristics; this is not acceptable since we know that often the vegetative characters are more easily affected by environment. As against this, natural classification systems developed, which were based on natural affinities among the organisms and consider, not only the external features, but also internal features, like ultra-structure, anatomy, embryology and phytochemistry. Such a classification for flowering plants was given by George Bentham and Joseph Dalton Hooker.
At present phylogenetic classification systems based on evolutionary relationships between the various organisms are acceptable. This assumes that organisms belonging to the same taxa have a common ancestor. We now use information from many other sources too to help resolve difficulties in classification. These become more important when there is no supporting fossil evidence. Numerical Taxonomy which is now easily carried out using computers is based on all observable characteristics. Number and codes are assigned to all the characters and the data are then processed. In this way each character is given equal importance and at the same time hundreds of characters can be considered. Cytotaxonomy that is based on cytological information like chromosome number, structure, behaviour and chemotaxonomy that uses the chemical constituents of the plant to resolve confusions, are also used by taxonomists these days.
1) In phylogenetic system of classification, it is believed that organisms belongs to the same taxa have ___________
a) Common character
b) Common ancestor
c) Different character
d) All of the above
2.) Linnaeus, gave theearliest artificial system of classification systems which was based on
(a) structure of leaves
(b) Androecium structure
(c) Colour of leaves
(d) All of the above
3) Why natural classification systems was developed, what was the need of it?
4) Define numerical taxonomy.
5) What are the basis of the phylogenetic classification system?
Answer key
1) b
2) b
3) The earliest systems of classification was totally based upon superficial external vegetative and sexual characteristics, such as habit, colour, number and shape of leaves, etc. this is not acceptable since we know that often the vegetative characters are get easily affected by environment. As against this, natural classification systems was developed.
4) Natural classification systems were based on natural affinities among the organisms and consider, not only the external features, but also internal features, like ultra-structure, anatomy, embryology and phytochemistry. Such a classification for flowering plants was given by George Bentham and Joseph Dalton Hooker.
Numerical taxonomyis the branch of taxonomy in which mathematical methods are used to evaluate observable difference and similarities between taxonomic groups of plant.
5) Phylogenetic classification system indicates evolutionary as well as the genetic relationship among organism, it is based on the fossil record, biochemical, anatomical, morphological, embryological, physiological, genetics, Karyotype, and other studies.
CASE 2
Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic (both fresh water and marine) organisms. They occur in a variety of other habitats: moist stones, soils and wood. Some of them also occur in association with fungi (lichen) and animals (e.g., on sloth bear). The form and size of algae is highly variable, ranging from colonial forms like Volvox and the filamentous forms like Ulothrix and Spirogyra.
The algae reproduce by vegetative, asexual and sexual methods. Vegetative reproduction is by fragmentation. Asexual reproduction is by the production of different types of spores, the most common being the zoospores. Sexual reproduction takes place through fusion of two gametes. The algae are divided into three main classes: Chlorophyceae, Phaeophyceae and Rhodophyceae.
The members of chlorophyceae are commonly called green algae. The plant body may be unicellular, colonial or filamentous. They are usually grass green due to the dominance of pigments chlorophyll a and b. The chloroplasts may be discoid, plate-like, reticulate, cup-shaped, spiral or ribbon-shaped in different species. Most of the members have one or more storage bodies called pyrenoids located in the chloroplasts. Green algae usually have a rigid cell wall made of an inner layer of cellulose and an outer layer of pectose. Vegetative reproduction usually takes place by fragmentation or by formation of different types of spores. Asexual reproduction is by flagellated zoospores produced in zoosporangia. The sexual reproduction shows considerable variation in the type and formation of sex cells and it may be isogamous, anisogamous or oogamous. Some commonly found green algae are: Chlamydomonas, Volvox, Ulothrix, Spirogyra and Chara.
The members of phaeophyceae or brown algae are found primarily in marine habitats. They show great variation in size and form. They possess chlorophyll a, c, carotenoids and xanthophylls. They vary in colour from olive green to various shades of brown depending upon the amount of the xanthophyll pigment, fucoxanthin present in them. Food is stored as complex carbohydrates, which may be in the form of laminarin or mannitol. The vegetative cells have a cellulosic wall usually covered on the outside by a gelatinous coating of algin. Vegetative reproduction takes place by fragmentation. Asexual reproduction in most brown algae is by biflagellate zoospores that are pear-shaped and have two unequal laterally attached flagella. Sexual reproduction may be isogamous, anisogamous or oogamous. The common forms are Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus.
1) ______________ is the colonial form of algae.
a) Ulothrix
b) Spirogyra
c) Volvox
d) Chara
2) _______________ are a micro compartment storage bodieslocated in the chloroplasts of algae.
a) Align
b) Pyrenoids
c) Carragen
d) Mannitol
3.) Name the animal which shows mutual association with algae.
4) Give reason – Why members of chlorophyceae class are named as green algae?
5) Name the pigment which determine the colour of the brown algae.
Answer key
1) c
2) b
3) Sloth bear and algae share a mutual association, as the algae grows on the fur of sloth bear for shelter and water.
4) The members of chlorophyceae class have dominance of pigments chlorophyll a and b. Due to the dominance of these pigments they appear green, hence they are named as green algae.
5) The presence of Xanthophyll pigment and fucoxanthin pigment levels determine the colour of the brown algae.
CASE 3
The gymnosperms are plants in which the ovules are not enclosed by any ovary wall and remain exposed, both before and after fertilisation. The seeds that develop post-fertilisation, are not covered, i.e., are naked. Gymnosperms include medium-sized trees or tall trees and shrubs. One of the gymnosperms, the giant redwood tree Sequoia is one of the tallest tree species. The roots are generally tap roots. Roots in some genera have fungal association in the form of mycorrhiza (Pinus), while in some others (Cycas) small specialised roots called coralloid roots are associated with N2 – fixing cyanobacteria. The leaves may be simple or compound. In Cycas the pinnate leaves persist for a few years. The leaves in gymnosperms are well-adapted to withstand extremes of temperature, humidity and wind. In conifers, the needle-like leaves reduce the surface area. Their thick cuticle and sunken stomata also help to reduce water loss.
The gymnosperms are heterosporous; they produce haploid microspores and megaspores. The two kinds of spores are produced within sporangia that are borne on sporophylls which are arranged spirally along an axis to form lax or compact strobili or cones. The strobili bearing microsporophylls and microsporangia are called microsporangiate or male strobili. The microspores develop into a male gametophytic generation which is highly reduced and is confined to only a limited number of cells. This reduced gametophyte is called a pollen grain. The development of pollen grains take place within the microsporangia. The cones bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili. The male or female cones or strobili may be borne on the same tree (Pinus). However, in cycas male cones and megasporophylls are borne on different trees. The megaspore mother cell is differentiated from one of the cells of the nucellus. The nucellus is protected by envelopes and the composite structure is called an ovule. The ovules are borne on megasporophylls which may be clustered to form the female cones. The megaspore mother cell divides meiotically to form four megaspores. One of the megaspores enclosed within the megasporangium develops into a multicellular female gametophyte that bears two or more archegonia or female sex organs. The multicellular female gametophyte is also retained within megasporangium.
1.) In gymnosperms, seeds that develop after fertilisation are ________________
a) Covered in ovary walls
b) Not covered in ovary walls
c) Covered in ovary sheath
d) None of the above
2.) Identify the correct characteristics of cycus
Characteristic 1 –Leaves pinnate for a few years
Characteristic 2 – Small specialised coralloid roots present
Characteristic 3 – Roots are associated with nitrogen fixing bacteria
Characteristic 4 – Male and female cone are present on different plant
a) Both 2 and 3
b) Only 2
c) 1, 2 and 3
d) All of the above
3) Name the special type of root found in cycus tree.
4) Why gymnosperms are referred as heterosporous group of plants.
5) What is the reason behind needle-like leaves adaptation in gymnosperms?
Answer key
1) b
2) d
3) In cycus, small specialised roots i.e. coralloid roots are found. Coralloid roots shows symbiotic association with Nitrogen – fixing cyanobacteria.
4) Gymnosperms are referred as heterosporous group of plants, because they produce haploid microspores and megaspores
5) The leaves in gymnosperms are well-adapted to survive in extremes of temperature, humidity and wind. The needle-like leaves reduce the surface area. Their thick cuticle and sunken stomata also help to reduce water loss.
CASE 4
Bryophytes are mostly terrestrial plants. They are found in moist shady places. But they need water for fertilization and completion of their life cycle. Hence they are called ‘amphibious plants’. The plant body of bryophytes is more differentiated than that of algae. It is thallus-like and prostrate or erect, and attached to the substratum by unicellular or multicellular rhizoids. They lack true roots, stem or leaves. They may possess root-like, leaf-like or stem-like structures. The main plant body of the bryophyte is haploid. It produces gametes, hence is called a gametophyte. The sex organs in bryophytes are multicellular. The male sex organ is called antheridium. They produce biflagellate antherozoids. The female sex organ called archegonium is flask-shaped and produces a single egg. The antherozoids are released into water where they come in contact with archegonium. An antherozoid fuses with the egg to produce the zygote. Zygotes do not undergo reduction division immediately. They produce a multicellular body called a sporophyte. The sporophyte is not free-living but attached to the photosynthetic gametophyte and derives nourishment from it. Some cells of the sporophyte undergo reduction division (meiosis) to produce haploid spores. These spores germinate to produce gametophyte.
They include approximately 960 genera and about 25,000 species. Life cycle of Bryophytes shows sporophytic and gametophytic stages. Vegetative plant body is thalloid or leafy which represents gametophytic generation. Spore producing capsule represents sporophytic generation. Bryophytes have root-like structures called rhizoids. Rhizoids are unicellular in liverworts while multicellular in mosses. Rhizoids absorb water and minerals and also help in fixation of thallus on the substratum. Bryophytes are divided into two groups : liverworts and mosses.
Liverworts (Hepaticeae) – These are lower members of Bryophyta. These are primitive group of Bryophytes. Gametophyte possesses flat plant body called thallus. The thallus is green, dorsiventral, prostrate with unicellular rhizoids. E.g. Riccia, Marchantia
Hornworts (Anthocerotae) – These member possess flattened thallus. The thallus produces horny structures which are called sporophytes hence the name hornworts. e.g. Anthoceros.
Mosses (Musci) – These are advanced members of Bryophyta which possess erect plant body. Gametophytic phase of the life cycle includes two stages namely; protonema stage and leafy stage. The protonema is prostrate green, branched and filamentous (it is also called juvenile gametophyte). It bears many buds. Leafy stage is produced from each bud. Thus protonema helps in the vegetative propagation. The leafy stage has erect, slender stem like (Cauloid) main axis bearing spiral leaf like structures (Phylloid). It is fixed in soil by multicellular branched rhizoids. This stage bears sex organs. Vegetative reproduction takes place by fragmentation and budding in secondary protonema. e.g. Funaria, Polytrichum, Sphagnum, etc
Bryophytes in general are of little economic importance but some mosses provide food for herbaceous mammals, birds and other animals. Species of Sphagnum, a moss, provide peat that have long been used as fuel, and as packing material for trans-shipment of living material because of their capacity to hold water. Mosses along with lichens are the first organisms to colonise rocks and hence, are of great ecological importance. They decompose rocks making the substrate suitable for the growth of higher plants. Since mosses form dense mats on the soil, they reduce the impact of falling rain and prevent soil erosion. The bryophytes are divided into liverworts and mosses.
1.) Lower members of bryophytes are represented by _____________ group of bryophytes
A) Mosses
b) Liverworts
c) Hornworts
d) Both a and b
2.) In bryophytes, capsule which produces spore represents ____________
a) Amphibious generation
b) Gametophytic generation
c) Sporophytic generation
d) None of the above
3) Define rhizoids and give its functions
4) Enlist the name of the male and female sex organ present in bryophytes and what they produce.
5) Name the group of plant which are commonly called as “Amphibians of Plant Kingdom” and why?
Answer key
1) b
2) c
3) Bryophytes have root-like structures called rhizoids. Rhizoids absorb water and minerals and also help in fixation of thallus on the substratum.
4) The male sex organ is called antheridium. They produce biflagellate antherozoids. The female sex organ called archegonium is flask-shaped and produces a single egg.
5) Bryophytes are called as “amphibians of the plant kingdom” because they are terrestrial plants, but require water to complete their life cycle at the time of sexual reproduction.
CASE 5
In plants, both haploid and diploid cells can divide by mitosis. This ability leads to the formation of different plant bodies – haploid and diploid. The haploid plant body produces gametes by mitosis. This plant body represents a gametophyte. Following fertilisation the zygote also divides by mitosis to produce a diploid sporophytic plant body. Haploid spores are produced by this plant body by meiosis. These in turn, divide by mitosis to form a haploid plant body once again. Thus, during the life cycle of any sexually reproducing plant, there is an alternation of generations between gamete producing haploid gametophyte and spore producing diploid sporophyte.
Life cycle of a plant includes two phases or distinct generations namely sporophyte (2n) and gametophyte (n). Some special diploid cells of sporophyte divide by meiosis to produce haploid cells. These haploid cells divide mitotically to give rise to gametophyte. The gametophyte produces male and female gametes which fuse during fertilization to produce diploid zygote. It divides by mitosis to form diploid sporophyte. The sporophytic and gametophytic generations generally occur alternately in the life cycle of a plant. This phenomenon is called alternation of generations.Distinct alternation of these two generations is observed in Bryophytes.
However, different plant groups, as well as individuals representing them, differ in the following patterns:
- Sporophytic generation is represented only by the one-celled zygote. There are no free-living sporophytes. Meiosis in the zygote results in the formation of haploid spores. The haploid spores divide mitotically and form the gametophyte. The dominant, photosynthetic phase in such plants is the free-living gametophyte. This kind of life cycle is termed as haplontic. Many algae such as Volvox, Spirogyra and some species of Chlamydomonas represent this pattern.
- On the other extreme, is the type wherein the diploid sporophyte is the dominant, photosynthetic, independent phase of the plant. The gametophytic phase is represented by the single to few-celled haploid gametophyte. This kind of life cycle is termed as diplontic. An alga, Fucus sp., represents this pattern. In addition, all seed bearing plants i.e., gymnosperms and angiosperms, follow this pattern with some variations, wherein, the gametophytic phase is few to multi-celled.
- Bryophytes and pteridophytes, interestingly, exhibit an intermediate condition (Haplo-diplontic); both phases are multicellular. However, they differ in their dominant phases.A dominant, independent, photosynthetic, thalloid or erect phase is represented by a haploid gametophyte and it alternates with the shortlivedmulticelluler sporophyte totally or partially dependent on the gametophyte for its anchorage and nutrition. All bryophytes represent this pattern.
The diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. It alternates with multicellular, saprophytic/autotrophic, independent but short-lived haploid gametophyte. Such a pattern is known as haplo-diplontic life cycle. All pteridophytes exhibit this pattern. Interestingly, while most algal genera are haplontic, some of them such as Ectocarpus, Polysiphonia, kelps are haplo-diplontic. Fucus, an alga is diplontic.
1.) Identify the incorrect statement about haplontic life cycle pattern.
Statement 1 – Gametophytic phase is dominant phase in this life cycle
Statement 2 – Zygote acts as sporophyte
Statement 3 – haploid Spores form gametophyte by mitotic division
Statement 4 –Sporophytes are free-living
a) Statement 1 and 3 are incorrect
b) Statement 4 is incorrect
c) Statement 1 is incorrect
d) Statement 2 and 4 are incorrect
2) In diplonticlife cycle, gametophytic phase is represented by _________________
a) Haploid gametophyte
b) diploid gametophyte
c) Haploid sporophyte
d) Both a and c
3.) Name the plant or organism which represent the haplontic pattern of life cycle.
4.) What is mean by alternation of generations?
5.) What is mean by ,
- Diplontic life cycle
- Haplontic life cycle
- Haplo-diplontic life cycle
Answer key
1.) b
2.) a
3.) Many algae such as Volvox, Spirogyra and some species of Chlamydomonas represent haplontic pattern of life cycle.
4.) When sporophytic and gametophytic generations occur alternately in the life cycle of a plant. This phenomenon is called as alternation of generations.
5.) Diplontic life cycle – Here mitotic divisions occurs only in diploid cells. Gametes formed through meiosis are haploid in nature. The diploid zygote divide mitotically. In this process production of multicellular diploid organism or in the production of many diploid single cells takes place. E.g. Animals.
Haplontic life cycle – Here mitosis occurs in haploid cells. It results in the formation of single haploid cells or a multicellular haploid organism. These forms produce the gametes through mitosis. Zygote is formed after fertilization. This cell is the only diploid cell in the entire life cycle of the organism. Thus the same zygotic cell later undergoes meiosis. E.g. Some Algae and Fungi.
Haplo-diplontic life cycle – Here mitosis occur in both diploid and haploid cells. These organisms undergo through a phase in which they are multicellular and haploid (the gametophyte), and a phase in which they are multicellular and diploid (the sporophyte). E.g. Land plants and in many algae.