Practice Corner MCQs

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(a) Before 1969, all the organisms had been divided into two groups-plants and animals, mainly on the basis of presence or absence of cell wall. Linnaeus (Father of taxonomy) founded two kingdoms – Kingdom Plantae and Kingdom Animalia in his two kingdom system of classification.

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(d) R.H. Whittaker proposed a Five Kingdom Classification. The kingdoms defined by him were named Monera, Protista, Fungi, Plantae, and Animalia. The main criteria for classification used by him include cell structure, thallus organization, mode of nutrition, reproduction and phylogenetic relationships. So the correct option is “All of these”.

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(b) In Whittaker’s five kingdom system of classification, eukaryotes are distributed among four kingdoms: Protista, Plantae, Fungi and Animalia. Kingdom Monera includes all prokaryotes, e.g., mycoplasma, bacteria, actinomycetes and cyanobacteria (blue green algae).

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(b)

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(c) Bacteria are grouped under four categories based on their shapes: the spherical coccus (pl.: cocci), the rod-shaped bacillus (pl.: bacilli), the comma-shaped vibrium (pl.: vibrio) and the spiral shaped spirillum (pl.: spirilla).

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(b)Methanogens are a type of archaebacteria which are strict anaerobes. Nutritionally they are autotrophs which obtain both energy and carbon from decomposition products. They occur in marshy areas where they convert formic acid and carbon dioxide into methane with the help of hydrogen. This capability is commercially exploited in the production of methane and fuel gas inside gobar gas plants, e.g., Methanobacterium, Methanococcus.

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(c) In a bacterial cell, membrane bound cell organelles as found in eukaryotes are absent. Various structures present in the cytoplasm of a prokaryotic cell include mesosomes, 70S ribosomes, nucleoid, plasmids, gas vacuoles, food reserve, etc.

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(a) Cyanobacteria or blue-green algae are Gram +ve photosynthetic prokaryotes which perform oxygenic photosynthesis. Cyanobacteria are classified under Kingdom Monera.

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(d) Photosynthetic pigments of cyanobacteria include chlorophyll a, carotenoids and phycobilins.

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(a) Because of their activity of fixing atmospheric nitrogen and make it available to plants(as plants cannot directly use nitrogen). This improves the yield of the crop and also reduces the cost of nitrogen fertilizers. Eg Anabena, Nostoc. So the correct option is “\(\mathrm{N}_{2}\) fixation”.

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(a) A heterocyst is a cyanobacterial cell that is segregated and conducts nitrogen fixation. Under aerobic conditions, the heterocysts serve as the sites for the fixation of nitrogen. In response to a lack of fixed nitrogen, they are created.
The mucilaginous sheath has a major role that covers and protects the cells from damage, resulting in cells that are immune to cell degradation. Before entering the process of DNA extraction, removing the mucilaginous sheath becomes a crucial step.

Nostoc is a dark blue-green, jelly-like organism sometimes found in soggy home lawns. Nostoc is in the group with the common name ‘blue-green algae’, a group often called cyanobacteria. Nostoc cyanobacteria form single-celled threadlike structures called filaments.

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(d) The cyanobacteria (also referred to as blue-green algae)have chlorophyll a similar to green plants and are photosynthetic autotrophs. The cyanobacteria are unicellular, colonial or filamentous fresh-water marine or terrestrial algae. The colonies are generally surrounded by a gelatinous sheath. They often form blooms in polluted water bodies. Some of these organisms can fix atmospheric nitrogen in specialized cells called heterocysts, e.g Nostoc and Anabaena. So the correct option is “All of these”.

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(a) In the given cyanobacterial diagram A represents naked DNA while B represents thylakoid. So, the correct option is ‘A – Naked DNA, B – Thylakoid’.

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(b) Chemosynthetic bacteria are organisms that use inorganic molecules such as sulphates & ammonia as a source of energy. So, the correct option is ‘Chemosynthetic autotrophic’.

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(d) Kingdom Monera includes prokaryotes – mycoplasma, bacteria, actinomycetes and cyanobacteria or blue green algae.

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(d) Saprophytic bacteria are free living bacteria which obtain their food from organic remains, e.g., corpses, animal excreta, fallen leaves, vegetables, fruits, meat, jams, jellies, bread and other products of plant and animal origin. Aerobic breakdown of organic compounds is known as decay. In nature saprophytic bacteria along with saprotrophic fungi are the decomposers of organic remains.

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(d) Pathogen of cholera is Vibrio cholerae bacterium. Cholera is transmitted by contaminated water. Typhoid or enteric fever spreads through contaminated water in which bacterium Salmonella typhiis present. Citrus canker and crown gall are bacterial diseases of plants caused by Xanthomonas citri and Agrobacterium tumefaciens, respectively.

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(a) Reproduction in bacteria occurs by three methods – binary fission, sporulation and sexual reproduction. Binary fission is the most common method of bacterial multiplication under favourable conditions, in which a mature bacterium divides into two equal daughter cells.

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(a) Mycoplasma are classified under kingdom-Monera. There are two major groups of monerans, archaebacteria and eubacteria. Some other groups of monerans are mycoplasma, rickettsiae and actinomycetes. Mycoplasma are the simplest and the smallest free-living prokaryotes.

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(c) The Mycoplasma are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasmas are pathogenic in animals and plants.
So the correct option is “They cannot survive without oxygen”.

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(b) Bacterial plasma membrane or plasmalemma has a structure similar to that of a typical membrane. It is made of a phospholipid bilayer with proteins of various types (extrinsic, integral, transmembrane). Archaebacteria are a group of most primitive prokaryotes which are able to survive in extremely hostile conditions. Their cell membranes are different from eubacteria and are characterised by the presence of a monolayer of branched chain lipids.

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(b) Actinomycetes are a class of bacteria not fungi, numerous antibiotics are created from the bacteria. So, the correct option is ‘A large number of antibiotics are produced by actinomycetes (e.g, Streptomyces), which are a class of fungi.’

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(c) Although all single-celled eukaryotes (except some unicellular algae, e.g., Chlamydomonas, Chlorella etc., fungi, e.g., yeasts and animals, which are placed in their respective kingdoms along with their closely related multicellular organisms) are placed in Kingdom Protista, yet its boundaries are not well defined.

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(d) All single-celled eukaryotes are placed under Protista, but the boundary of this kingdom are not well defined. Protista includes Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds and Protozoans.
So the correct option is “All of these”.

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(c) All single-celled eukaryotes are placed under Protista, but the boundaries of this kingdom are not well defined. Members of Protista are primarily aquatic. Being eukaryotes, the protistan cell body contains a well-defined nucleus and other membrane-bound organelles.
So the correct option is “aquatic”.

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(d) Protista is a kingdom in which single-celled eukaryotic organisms are present. Protists don’t have well defined cell boundaries due to the presence of the nucleus. They form a link in different categories. The cell body of Protista contains a well-defined nucleus and membrane-bound organelles. Along with that some have cilia and some have flagella are also present that help in movement. Protist reproduces asexually as well as sexually depending on the external environment. So they show similarity with Plantae, fungi, and Animalia because they all are also eukaryotes. So the correct answer is d.

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(a) Monera is unicellular organisms having prokaryotic cellular structure while protista is also unicellular organism having a eukaryotic cellular organization. So, the correct option is ‘Monera – Includes unicellular prokaryotes; Protista – Includes multicellular eukaryotes’.

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(a) Chrysophytes include diatoms and desmids. They belong to the division Chrysophyta/Bacillariophyta.

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They are also called golden-brown algae.
(a) They are plant-like protists found in marine and fresh water environment. Since they live in watery environment and are commonly found in lakes hence they are a type of planktons.
Hence, Chrysophytes are planktons.

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(b) The body of diatoms is covered by a transparent siliceous shell (silica deposited in cell wall) known as frustule. The frustule is made of two valves, epitheca and hypotheca. The two valves fit together like a soap box.

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(b) In diatoms, the cell walls form two thin overlapping shells, which fit together as in a soapbox. The walls are embedded with silica and thus the walls are indestructible. Thus, diatoms have left behind large amount of cell deposits in their habitat; this accumulation over billions of years is referred to as ‘diatomaceous earth’. So the correct option is “diatomaceous earth”.

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(d) The cell walls of diatoms are embedded with silica and thus the walls are indestructible. Thus, diatoms have left behind a large number of cell deposits in their habitat; this accumulation over billions of years is referred to as ‘diatomaceous earth’. Being gritty this soil is used in polishing, filtration of oils and syrups.
So the correct option is “biogas production”.

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(c) Dinoflagellates – These organisms are mostly marine and photosynthetic. Whereas Euglenoids are freshwater (majority).
So the correct option is “marine and photosynthetic”.

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(d) These features are matching to the Kingdom Protista. Protista are single-celled eukaryotes. Members of Protista are primarily aquatic. Being eukaryotes, the protistian cell body contains a well-defined nucleus and other membranebound organelles. Protista includes Chrysophytes, Dinoflagellates, Euglenoids, Slime molds, and Protozoans. Most of the Dinoflagellates have two flagella, one lies longitudinally and the other transversely in a furrow between the wall plates.
So the correct option is “Dinoflagellate”.

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(b) In the given figure, we can observe that there are two flagella; one lies longitudinally and the other transversely in a furrow between the wall plates. So this is the characteristics feature of Dinoflagellates. So the correct option is “Dinoflagellates”.

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(a) These organisms are mostly marine and photosynthetic. They appear yellow, green, brown, blue, or red depending on the main pigments present in their cells. The cell wall has stiff cellulose plates on the outer surface Most of them have two flagella: one lies longitudinally and the other transversely in a furrow between the wall plates. Very often, red dinoflagellates undergo such rapid multiplication that they make the sea appear red. So the correct option is “dinoflagellates”.

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(d) Protozoan, life form, generally single-celled and heterotrophic (utilizing natural carbon as a wellspring of vitality), having a place with any of the real ancestries of protists and, as most protists, ordinarily minuscule. All protozoans are eukaryotes and in this manner have a “genuine,” or layer-bound, core.
So, the correct option is ‘(v) only’.

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(d) Euglenoids are unicellular aquatic alga that belongs to the kingdom Protista. Many of these organisms exhibit characteristics of both plants and animals. In this many of them have 2 flagella that emerges out of the cytostome through cytopharynx and are motile. Out of the two flagella, one is short and the other one is a long one. Instead of cell walls, they have a protein-rich pellicle that helps in maintaining the definite shape of the body. Nutrition in Euglena is accomplished by holophytic (able to synthesize organic compounds by photosynthesis) or saprophytic (those organisms get its nourishment from dead organisms) or both so they show the mixotrophic mode of nutrition.

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(c) The body of Euglena is covered by a plasma membrane followed by periplast or pellicle. At the place of union of the two branches, the flagellum bears a swelling called paraflagellar body (photoreceptor). The posterior end is pointed. The anterior end of the cell is blunt and bears an eccentric cytostome (mouth). At one end of the reservoir, the cytoplasm contains an orange-red stigma (eye spot). Pyrenoids (proteinaceous bodies) may be present in the chloroplasts. The endoplasm contains several paramylum bodies.

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(a) Correct answer is (a) Both statements  1 and 2 are correct.

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(a) Euglena is a class of single-cell flog eukaryotic. The species Euglena gracilis has been utilized widely in the research center as a model creature. Most types of Euglena have photosynthesizing chloroplasts inside the body of the cell, which empower them to nourish via autotrophy, similar to plants.
So, the correct option is ‘Euglena is a flagellate organism.’.

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(b) Slime moulds do not have chlorophyll. They are surrounded by the plasma membrane only (somatic parts are without cell walls). The slime moulds live usually amongst decaying vegetation. They are quite common on Iawns and moist fields. They exhibit wide range of colouration. They have phagotrophic or saprotrophic nutrition.

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(a) Phytoplankton has two principal classes: diatoms and dinoflagellates. Diatoms are the most well-known type of phytoplankton in the sea. Euglena is mixotrophs implying that they are the two autotrophs and heterotrophs. Ooze molds fall into two essential sorts: cells, for instance, Dictyostelium, and plasmodia.
So, the correct option is ‘A-(ii), B-(iv), C-(i), D-(iii)’.

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(a) A free-living thalloid body of the acellular slime moulds is called plasmodium. The plasmodium is wall-less mass of multinucleate protoplasm covered by slime.

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(d) Slime moulds are saprophytic protists having plasmodium as a free-living thalloid body. Plasmodium is a wall-less mass of multinucleate protoplasm covered by slime. During unfavourable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips. These spores are dispersed by air currents.

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(b) Entamoeoa histolytica resides in the upper part of the human large intestine and causes the disease amoebic dysentery or amoebiasis. The symptoms of the disease are abdominal pain, and repeated motions with blood and mucus.

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(b) Trypanosoma gambiense, causes Gambian sleeping sickness. The parasite is transmitted by blood-sucking tse-tse fly, Glossina palpalis. Leishmania donovani causes kala-azar or dumdum fever (= visceral ieishmaniasis). The parasite is transmitted by sandfly, Phlebotomus argentipes and other species. Causal organisms of both diseases belong to flagellated protozoans of Kingdom Protista.

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(d) The given figure is of Trypanosoma gambiense that belongs to flagellated protozoans of Kingdom Protista.

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(c) Paramecium is a free-living ciliate which is found in freshwater. The most widely distributed species are Paramecium caudatum and Paramecium aurelia. The cilia of the extreme posterior end are longer and form a bunch called caudal tuft.

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(c) All sporozoans are endoparasites. Sexual reproduction takes place through syngamy. Asexual reproduction occurs through multiple fission. Under unfavourable conditions, they form cysts. Examples – Plasmodium (the malarial parasite), Monocystis, etc.

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(d) Gonyaulax spinifera is a dinoflagellate. 

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(c) Fungi is a large kingdom of over 100,000 species. They are achlorophyllous, heterotrophic, spore-forming, non-vascular, eukaryotic organisms which often contain chitin or fungai cellulose in their walls and possess glycogen as food reserve.

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(c) Filamentous parasites could contain more than one core in a coenocytic mycelium. A coenocyte ability as a solitary facilitated unit made out of several cells connected basically and practically, i.e. Through hole intersections. Parasitic mycelia where hyphae need septa are frequently called “aseptate”. So, the correct option is ‘multinucleate, aseptate’.

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(c) In fungi, cell wall contains chitin or fungal cellulose along with other polysaccharides, proteins, lipids, and a number of other substances. Chitin is basically made up of \(\mathrm{N}\)-acetyl glucosamine. In some fungi, cellulose is also present, either alone (e.g., Phytophthora and many other oomycetes) or along with chitin.

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(b) Asexual reproduction in fungi occurs through the formation of spores. Spores are single-celled propagules which separate from the parent organism and can get dispersed., e.g., zoospores, sporangiospores, chlamydospores, oidia, conidia, etc. Oospore is the product of sexual reproduction.

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(c) Sexually produced spores (or meiospores) are produced after meiosis in some fungi, e.g., ascospores, basidiospores, and oospores. Zoospores are motile spores produced asexually.

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(d) In Ascomycetes and Basidiomycetes, there occurs an intervening phase called dikaryophase, between plasmogamy and karyogamy. In this phase, the cells often contain two nuclei or dikaryons (n+n). Such cells are called dikaryotic cells.

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(b) In Ascomycetes and Basidiomycetes, the life cycle is completed in three phases instead of two-haplophase, dikaryophase, and diplophase (2 n). Haplophase by plasmogamy converts into dikaryophase where each cell has two haploid nuclei. Then karyogamy occurs converting dikaryophase to diplophase. Meiosis occurs in diplophase and haploid condition is regained.

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(b) Phycomycetes are characterised by the presence of coenocytic multinucleate and aseptate branched mycelium.

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(a) The fungus that lacks cross walls in mycelium is Phycomycetes because it grows like a single cell. The class Phycomycetes has been abolished and in its place.

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(b) Phycomycetes are characterised by aseptate coenocytic hyphae.

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(a) White rust occurs in crucifers and is characterised by the appearance of irregular white blisters containing conidiosporangia on the leaves and stems. White rust is caused by Albugo candida (Cystopus candidus).

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(c) The best-known antibiotic, called penicillin is obtained from both Penicillium notatum and P. chrysogenum.

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(d) In Penicillium, the asexual reproduction takes place by conidiospores.

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(b) In phycomycetes, the hyphae are aseptate, coenocytic and they form multinucleate gametes called coenogametes. Basidiomycetes to which Agaricus belongs has a layer in gills with basidia and paraphyses called hymenium.

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(a) In the majority of Ascomycetes, the common mode of asexual reproduction is through the formation of conidia (singular-conidium). Conidia are non-motile fungal mitospores that are produced exogenously from the tips and sides of hyphae called conidiophores.

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(c) The given figure is of Aspergillus. It belongs to Class Ascomycetes.

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(d) Sexual propagation in Basidiomycota happens in the fruiting body, in specific structures called basidia. The basidia are itself framed by plasmogamy between mycelia from two unique spores. Plasmogamy results in binucleate hyphae, that is, hyphae with two sorts of cores, one from each parent. So, the correct option is ‘All of these’.

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(b) The given figure is of Agaricus. It is an edible mushroom commonly used to make delicacies.

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(b) The correct option is ‘A – Mucor, B – Saccharomyces, C – Penicillium, D – Agaricus’.

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(c) Some members of Class Deuteromycetes are saprophytes or parasites while a larger number of them are decomposers of litter and help in mineral cycling. Some examples are Colletotrichum and Trichoderma.

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(d) Deuteromycetes is an artificial class of fungi that have been created to include all those fungi in which sexual stage is either absent or not known. Ustilago is a member of Basidiomycetes.

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(a) Morels are Ascomycetes with edible ascocarps that have fleshy sponge-like conical cap or pileus and a stalk-like stipe, e.g., Morchella esculenta (Vern. Gucchi), M. crassipes, M. deliciosia. Truffles are edible Ascomycetes with tuber-like subterranean ascocarps that are often dug out with the he!p of trained dogs and pigs, e.g., Tuber uncinatum. T.aestivum.

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(c) Bladderwort and Venus fly trap are insectivorous plants. Cuscuta is a parasite. Solanum is a photosynthetic green plant.

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(c) In plants, cellulosic cell wall is defining feature of plants only.

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(a) Kingdom Animalia includes all heterotrophic eukaryotic organisms that are multicellular and lack cell walls in their cells.

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(b) Virus (L. poison) is a non-cellular, infectious, nucleoprotein entity enclosed within a protein covering or coat. Viruses are characterised by having an inert crystalline structure outside the living cell.

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(c) TMV (Tobacco mosaic virus) is a ribovirus. It is rod-shaped measuring \(300 \times 20 \mathrm{~nm}\). It is made up of ssRNA and proteinaceous covering capsid with 2130 capsomeres, which are helically arranged to form a hollow cylinder.

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(a) Stanley first isolated and crystallized virus. he shared the Nobel Prize with Northrop. So, the correct option is ‘W.M. Stanley’.

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(b) The name virus was given by Pasteur. 

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(d) Virus is an obligate parasite and is inert outside the host cell. An inert virus outside the host is called virion. It can be crystallised and stored indefinitely.

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(c) Viruses are non-cellular, infectious, nucleoprotein entity that cannot be grown in culture medium as they lack their own machinery. Once, they infect a cell, they take over the machinery of the host cell to replicate themselves, killing the host.

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(d) The given figure is of bacteriophage, a virus that infects bacteria.

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(d) In humans, viruses cause diseases like measles, smallpox, mumps, poliomyelitis, rabies, hepatitis, dengue, encephalitis, AIDS, common cold, flu, herpes, SARS (severe acute respiratory syndrome), bird flu (H5NI), swine flu (H1N1), etc.

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(c) Dmitri Ivanovsky discovered that the cause of tobacco mosaic disease could pass through a porcelain filter. Temin and Baltimore discovered retrovirus and the phenomenon of Teminism in 1972.

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(c) In plants, viruses cause diseases like potato mosaic, pumpkin mosaic, apple mosaic, tulip mosaic (broken tulip), bhindi yellow vein mosaic, potato leaf roll, papaya leaf curl, banana bunchy top, tomato bunchy, rice tungro, etc.

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(a) Fungus Colletotrichum falcatum produces red rot of sugarcane which is conspicuous on leaf midribs as well as in canes. It reduces the juice content of canes and brings about the withering of leaves.

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(b) The Potato axle tuber viroid was the primary viroid to be distinguished. PSTVd is a little, round RNA atom firmly identified with the chrysanthemum stunt viroid. Present inside the viroidal RNA is the Pospiviroid RY theme stem circle. The common hosts are potatoes and tomatoes. So, the correct option is ‘Viroid’.

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(c) Lichens serve as an example of symbiosis (mutualism). They constitute the pioneer community in the case of lithosere. Planktons are pioneers in hydrosere.

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(d) Prions are highly resistant glycoprotein particles which function as infectious agents. They are formed due to mutation in the gene PRNP. Prions can also act as catalyst converting normal protein into prion state.

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(d) The protein coat called capsid made of small subunits called capsomeres, protects the nucleic acid. These capsomeres are arranged in helical or polyhedral forms.