Assertion Reason Questions for Biology Chapter 2 Biological Classification

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Directions: In the following questions, a statement of assertion is followed by a statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

Q.1. Assertion : Bacteria are prokaryotic.
Reason : Bacteria do not possess true nucleus and membrane bound cell organelles.

Answer Answer: (a) Bacterial cell is prokaryotic. It lacks true nucleus and membrane bound organelles.

Q.2. Assertion : Bacterial photosynthesis occurs by utilizing wavelength longer than 700 nm.
Reason : Here reaction centre is P-890.

Answer Answer: (b) Bacteria utilize the wavelengths longer than 700 nm for photosynthesis and the reaction centre is P-890 the reductant is NADH + H+. In bacteria, donor may be H2S or malate or succinate.

Q.3. Assertion : Sand fly transmits Kala-azar.
Reason : In Kala-azar, the parasite damages the brain.

Answer Answer: (c) Leishmania donovani causes kala-azar. The parasite is transmitted by sandfly. The parasite lives inside the cells of liver, spleen, lymph glands, white blood corpuscles and inner wall cells of blood capillaries. In sleeping sickness disease, the parasite damages the brain.

Q.4. Assertion : Escherichia coli, Shigella sp. and Salmonella sp. are all responsible for diarrhoeal diseases.
Reason : Dehydration is common to all types of diarrhoeal diseases and adequate supply of
fluids and electrolytes should be ensured.

Answer Answer: (b) E. coli, Shigella sp. and Salmonella sp. causes diarrhoea. It is due to intake of contaminated water.

Q.5. Assertion : Gram-negative bacteria do not retain the stain when washed with alcohol.
Reason : The outer face of the outer membrane of gram-negative bacteria contains lipopolysaccharides, a part of which is integrated into the membrane lipids.

Answer Answer: (a) Gram negative bacteria contain lipopolysaccharide in its membrane.

Q.6. Assertion: Two kingdom classification was insufficient.
Reason: Majority of organisms failed to fall into either of the categories in two kingdom classification.

Answer Answer: (a) Two kingdom classification (founded by Linnaeus) worked well for a long time. However, this system failed to distinguish between the eukaryotes and prokaryotes, unicellular and multicellular organisms, photosynthetic and non-photosynthetic organisms. Although, classification of organisms (into plants and animals) was easily done and was easy to understand, but a large number of organisms did not fall into either category. Hence, the two kingdom classification used for a long time was found inadequate.

Q.7. Assertion: Archaebacteria are able to survive in harsh habitats.
Reason: Archaebacteria survive in extreme conditions due to the presence of peptidoglycan in their cell wall.

Answer Answer: (c) Archaebacteria are special since they live in some of the most harsh habitats such as extreme salty areas (halophiles), hot springs (thermoacidophiles) and marshy areas (methanogens). Archaebacteria differ from other bacteria in having a different cell wall structure and this feature is responsible for their survival in extreme conditions. Archaebacteria are characterised by absence of peptidoglycan in their cell wall. Instead cell wall contains protein and non cellulosic polysaccharide.

Q.8. Assertion: Several ruminant animals contain methanogens within their gut.
Reason: Methanogens help in the production of methane from dung of ruminants.

Answer Answer: (b) Methanogens occur in marshy areas where they convert formic acid and carbon dioxide into methane with the help of hydrogen. Some of the methanogen archaebacteria live as symbionts (e.g., Methanobacterium) inside rumen or first chamber in the stomach of herbivorous animals that chew their cud (ruminants, e.g., cow, buffalo) and thus, helps in production of methane from dung of these animals. These archaebacteria are helpful to the ruminants in fermentation of cellulose.

Q.9. Assertion: The nitrogen-fixing bacteria in leguminous plant nodules live as symbionts.
Reason: Leg-haemoglobin synthesized by leguminous plants protect bacteria.

Answer Answer: (a) Rhizobium form a symbiotic association with roots of leguminous plants producing root nodules. These bacteria reside inside the nodules and reduce atmospheric nitrogen (N2) to ammonia. The fixed nitrogen is taken up by plant. In return, the plant provides both nutrients and protection to bacteria.

Q.10. Assertion: Bacteria are classified among plants.
Reason: They have cell walls.

Answer Answer: (a) Plant cells are characterized by the presence of a rigid cell wall on the basis of which they can be differentiated from animal cells. Hence, in two kingdom classification, bacteria were classified among plants. However, according to the five-kingdom classification, bacteria are grouped under kingdom Monera.

Q.11. Assertion: Bacteria do not always move with the help of flagella.
Reason: Rotary motion of flagellum is employed by flagellated bacteria for movement.

Answer Answer: (b) Myxobacteria do not have flagella and move by gliding movement.

Q.12. Assertion: Some bacteria have the capacity to retain Gram stain after treatment with acid alcohol.
Reason: They are known as gram positive as they are attracted towards positive pole under influence of electric current.

Answer Answer: (c) The cell wall of Gram-negative bacteria contains alcohol-soluble lipid, while the cell wall of Gram-positive bacteria lacks the lipids and therefore resist decolourisation and retain the primary stain, appearing violet. Gram-negative bacteria are decolorized by organic solvents and therefore, take the counter stain, appearing red. Gram + ve bacteria are not attracted towards positive pole under influence of electric current.

Q.13. Assertion: Chemosynthesis is not carried out by autotrophic bacteria.
Reason: Chemosynthetic bacteria trap the small amount of energy released from inorganic compound’s oxidation to use in the reactions that synthesize carbohydrates.

Answer Answer: Chemosynthetic bacteria are without photosynthetic pigments. For the synthesis of their own organic food (carbohydrates), they obtain carbon from Solutions CO2 of the atmosphere and necessary energy from oxidation of inorganic or organic compounds, such as hydrogen sulphide (H2S), ferrous compounds (Fe2+), molecular hydrogen (H2), ammonia (NH3) and nitrites (NO2 –).

Q.14. Assertion : Exotoxins are released by Gram +ve bacteria causing diseases to animals.
Reason: Exotoxins are proteins that react with WBC of animals.

Answer Answer: (a) Mostly pathogenic gram +ve bacteria releases exotoxins outside the cell thus, killing the W.B.C. and causing disease

Q.15. Assertion: All food chains will come to stand still if bacteria disappear from earth.
Reason: Bacteria are only associated with the soil fertility and hardly any role for food chains.

Answer Answer: (c) Bacteria play an important and dual role by disposing off the dead bodies and wastes of organism and by increasing the fertility of soil.

Q.16. Assertion: Broad spectrum antibiotics are produced by Streptomyces.
Reason: Antibiotics can destroy microorganisms by inhibiting DNA replication or protein synthesis.

Answer Answer: (a) Streptomyces is used for production of broad spectrum antibiotics where living microorganism is capable of inhibiting or destroying other many types of microbes.

Q.17. Assertion: Bacterial cell wall is characterised by having mucopolysaccharides.
Reason: Acetyl muramic acid is an example of mucopolysaccharide.

Answer Answer: (d) Chemically bacteria consists of acetylglycosamine, acetyl muramic acid and a peptide chain of four or five amino acids. All these chemicals together form a polymer called peptidoglycan (= murein or mucopeptide). Some other chemical substances deposited on the cell wall are – teichoic acid, protein, polysaccharides, lipoproteins and lipopolysaccharides.

Q.18. Assertion: Anabaena inhabits root nodules of leguminous plants.
Reason: Leguminous plants are an example of symbiotic nitrogen fixation.

Answer Answer: (a) Anabaena found symbiotically in the root nodules of many leguminous plants helps in N2 fixation.

Q.19. Assertion: Bacillus butschli is true bacterium.
Reason: Its cell wall is composed of acetyl muramic acid.

Answer Answer: (a) Bacillus butschli is the Gram positive bacterium and its cell wall consist of acetyl muramic acid.

Q.20. Assertion: Pili are motile appendages found in some bacteria.
Reason: These participate in conjugation.

Answer Answer: (a) In some bacteria, nonmotile appendages called pili or fimbriae are also present. They take part in sexual reproduction, i.e., conjugation.

Q.21. Assertion: Cell secretion does not occur in bacteria.
Reason: Golgi complex is absent in bacteria.

Answer Answer: (a) Cell secretion occurs even in the prokaryotic cells (bacteria) in relation to the production of a variety of enzyme in the medium. While, golgi complex and other membrane bound organelles are absent in prokaryotes.

Q.22. Assertion: Methanogens are obligate anaerobes.
Reason: Halophiles are salt loving bacteria.

Answer Answer: (b) Methanogens are obligate anaerobes and used in biogas fermenters to produce methane. e.g. Methanobacterium, Methanococcus, etc. Halophiles are salt loving bacteria as they are found in to live in environments with a very high salt concentration.

Q.23. Assertion: Cyanobacteria are unicellular and colonial.
Reason: Blue green algae are chemosynthetic.

Answer Answer: (c) Cyanobacteria or Blue green algae are photosynthetic prokaryotes with chlorophyll a, carotenoids and phycobillins. They may be unicellular, colonial or filamentous and marine or terrestrial.

Q.24. Assertion: Cyanobacteria are photosynthetic autotrophs.
Reason: Cyanobacteria have chlorophyll a and b similar to green plants.

Answer Answer: (c) Cyanobacteria (also referred to as bluegreen algae) are photosynthetic autotrophs. They have chlorophyll a similar to green plants.

Q.25. Assertion : Plasmids are double-stranded extra chromosomal DNA.
Reason: Plasmids are possessed by eukaryotic cells.

Answer Answer: (c) In addition of bacterial chromosomes, many bacteria have accessory rings of DNA called plasmids. Plasmids are absent in eukaryotic chromosome.

Q.26. Assertion : Euglena is studied as an animal as well as a plant.
Reason :Euglena is more an animal than a plant.

Answer Answer: (b) Euglena is a typical example of mastigophora. It is phytoflagellate as it possesses both chloroplast and flagella. It is autotrophic in sunlight, but becomes heterotrophic in dark. Because of its two fold nutritional abilities, it is usually studied as a plant as well as an animal. But it is more an animal than plant because of
(a) The absence of cellulose cell wall overlying the plasma membrane.
(b) Presence of centriole.
(c) Reserve food is paramylon which is not a true starch.
(d) Response to various stimuli like an animal.

Q.27. Assertion : Amoeba contains a contractile vacuole.
Reason : It helps in both digestion and osmoregulation.

Answer Answer: (c) Contractile vacuole in Amoeba is a single, clear, rounded, pulsating structure which is filled with a watery fluid and enclosed by a unit membrane. It helps in the osmoregulation and excretory activities. Digestion in Amoeba occurs in the food vacuoles. These are spherical species small and large, contain water and food in various phases of digestion. As soon as the egestion of non digestible food occurs through body, these disappear.

Q.28. Assertion : Chemosynthesis is an autotrophic nutrition.
Reason : Chemoautotrophs contain chlorophyll pigments.

Answer Answer: (b) Chemoautotrophs developed the ability to synthesize organic molecules from inorganic raw materials. Chlorophyll pigments are present in photoautotrophs. The photo-autotrophs utilize the solar energy absorbed by them in synthesizing organic compounds. Certain chemoautotrophs include green sulphur bacteria.

Q.29. Assertion: Cell wall of chrysophytes are indestructible.
Reason: Cell walls of chrysophytes have layer of magnesium pectate embedded in it.

Answer Answer: (c) Chrysophytes include diatoms and golden algae (desmids). They are found in fresh water as well as in marine environments. The cell walls are embedded with silica and thus, the walls are indestructible.

Q.30. Assertion: The protoplasm of plasmodial slime mould is considered purest in the world.
Reason: Protoplasm of plasmodium is differentiated into an outer enucleated and central nucleated portions.

Answer Answer: (a) Vegetative part of slime moulds does not possess cell wall they either occur as free living amoeboid mass of protoplasm (plasmodium) or aggregation of amoebae (pseudoplasmodium). The protoplasm of plasmodial slime mould is considered as purest in the living world. It is differentiated into outer enucleated (hyaloplasm) and central nucleated portions. At maturity, it may contain several hundred to many thousand nuclei. The protoplasm is vacuolated.

Q.31. Assertion: Sporozoans may have silica shells on their surface.
Reason: Shells of sporozoans render protection from acidic environment of the host.

Answer Answer: (d) Sporozoans are endoparasites. Their body is covered with an elastic pellicle or cuticle. Thus, these do not have silica shells on their surface.

Q.32. Assertion: Euglena is called as plant animal.
Reason: Pellicle of Euglena is made up of cellulose and not protein.

Answer Answer: (c) Euglena is studied as plant as well as animal. It is called plant animal. Plant characters of Euglena are presence of chloroplasts with chlorophyll and holophytic (photosynthetic) nutrition in presence of light while, animal characters of Euglena are presence of pellicle which is made up of proteins and not of cellulose, presence of stigma and paraflagellar body (photosensitive structures), presence of contractile vacuole (not found in plants) and presence of longitudinal binary fission.

Q.33. Assertion: Chemosynthetic autotrophic bacteria oxidise various inorganic substances.
Reason: Energy released during oxidation is used in ATP production.

Answer Answer: (b) Chemoautotrophic bacteria are able to manufacture their organic food from inorganic raw materials with the help of energy derived from exergonic chemical reactions involving oxidation of an inorganic substance present in the external medium. The chemical energy obtained from oxidation reaction is trapped in ATP molecules.

Q.34. Assertion: Slime moulds show alternation of generation.
Reason: The sporangia bearing slime moulds represent haplophase.

Answer Answer: (a) Slime moulds exhibit alternation of generation. The diploid plasmodium is a sporophyte. Under certain conditions, it bears sporangia. These sporangia bearing plasmodium and spore producing sporangia constitute the sporophyte generation. It is a diplophase reduction division which takes place at the time of differentiation of resting spore. The resting spores germinate to produce the haploid, uninucleate swarm cells or myxamoebae. The latter meet and fuse in pairs to form a zygote. The haploid resting spores and the swarm cells or myxamoebae represent the haploid or gametophyte generation.

Q.35. Assertion: Trichomonas vaginalis causes infection only in women.
Reason: Trichomonas buccalis lives in the buccal cavity.

Answer Answer: (b) Trichomonas vaginalis infects vagina of women and causes the disease known as leucorrhoea. In males, the parasite produces irritation in urethra. Trichomonas buccalis resides in the buccal cavity, which is nearly harmless

Q.36. Assertion: Erythrocytic merozoites form gametocytes.
Reason: Gametocytes are of two types – male and female.

Answer Answer: (b) Some erythrocytic merozoites enter fresh RBCs and form rounded gametocytes (gamonts). The gametocytes are of two types – (i) Smaller male gametocytes or microgamete and (ii) Larger female gametocytes or macrogamete.

Q.37. Assertion: Plasmodium causes disease in female Anopheles mosquitoes.
Reason: Female Anopheles mosquitoes feed on plasmodial blood.

Answer Answer: (d) The sexual phase of the malarial parasite occurs in the Anopheles mosquito. As the female Anopheles mosquitoes feed on blood, only they can serve as vector hosts of malarial parasites. The parasite does not harm the mosquito.

Q.38. Assertion: Malarial fever appear at merozoite stage of Plasmodium.
Reason: The infective stage of Plasmodium is sporozoite.

Answer Answer: (b) When the mosquito bites man, sporozoites present in the salivary gland of female Anopheles mosquito are injected into the blood of the man. The erythrocytic schizont gives rise to merozoites. Malaria fever occurs when schizonts in red blood corpuscles burst and set free their contained merozoites and malarial pigment (haemozoin) in the blood plasma.

Q.39. Assertion: Schizogony is an asexual reproduction of female Anopheles mosquito.
Reason: It takes place only in human liver cells.

Answer Answer: (c) Schizogony is an asexual reproduction in which schizont is formed. From the human blood, sporozoites enter the liver cells. The sporozoite grows in size to become a rounded schizont called cryptozoite. The latter divides to form cryptomerozoites. The cryptomerozoites formed during preerythrocytic schizogony may enter the human RBCs to start the erythrocytic schizogony, while some of them enter new liver cells to repeat hepatic (liver) schizogony.

Q.40. Assertion: Kingdom-Protista forms a link between monerans and and the other organism like plants, animal and fungi.
Reason: Protist reproduce sexually and asexually by a process involving cell fusion and zygote formation.

Answer Answer: (b) Phylogenetically the Kingdom-Protista acts as a connecting link between the prokaryotic Kingdom- Monera and the complex multicellular kingdom- Fungi, Plantae and Animalia. They reproduce asexually and sexually.

Q.41. Assertion: Euglena cannot be classified on the basis of two kingdom system.
Reason: Euglena is a plant due to presence of chlorophyll.

Answer Answer: (c) Euglena is a green coloured, single celled organism, which moves like animals. Some taxonomists considered it as a plant and included it in the plant kingdom on the basis of chlorophyll, while other included it in the animal kingdom along with the flagellated protozoans because of the locomotion by flagella.

Q.42. Assertion: The protist feeds on red blood corpuscles.
Reason: Amoebiasis is caused by Amoeba

Answer Answer: (c) Person suffering from amoebic dysentery has repeated blood mixed with slimy and foul smelling motions. The protist feeds on red blood corpuscles by damaging the wall of large intestine and reaching the blood capillaries.

Q.43. Assertion : Aflatoxins are produced by Aspergillus flavus.
Reason : These toxins are useful to mankind.

Answer Answer: (c) Aflatoxins, are produced by Aspergillus flavus. Contaminated food is the main source of infection. This toxin causes aflatoxicosis which may lead to haemorrhage and diseases of liver.

Q.44. Assertion : Saccharomyces ellipsoidens is Wine yeast and Saccharomyces cerevisiae is Baker’s yeast.
Reason :Yeast is used to make dry ice.

Answer Answer: (b) The two common yeasts used by brewing industry are Saccharomyces cerevisiae (Beer or Baker’s yeast) and S. ellipsoidens (Wine yeast). In the baking or brewing industry, CO2 is the useful product. It is collected, solidified and sold as “dry ice”.

Q.45. Assertion : Neurospora is commonly called water mould.
Reason : It belongs to basidomycetes fungi.

Answer Answer: (d) Neurospora belongs to class ascomycetes in which ascospores are produced in sac like asci . Neurospora is commonly called as pink or red bread mould. It can be grown easily in laboratory conditions so, used in genetics experiments.

Q.46. Assertion: Phycomycetes are commonly known as sac fungi.
Reason: In phycomycetes, ascospore (sexual spores) are produced endogenously in sac like asci.

Answer Answer: (d) Ascomycetes is commonly known as sacfungi. Sexual spores of Ascomycetes are produced endogenously in sac like asci. Members of Phycomycetes are found in aquatic habitats and on decaying wood in moist and damp places or as obligate parasites on plants

Q.47. Assertion: Deuteromycetes is known as fungi imperfecti.
Reason: In Deuteromycetes, only the asexual phase is known.

Answer Answer: (a) Deuteromycetes are commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known and perfect or sexual stage is either absent or not known.

Q.48. Assertion: “Fungi imperfecti” does not show alternation of generation.
Reason: The diploid phase is present in only zygote.

Answer Answer: (c) Fungi imperfecti is that group of fungi where only the imperfect stage (asexual stages) is present. The only known method of reproduction is by conidia (asexual reproduction). As sexual reproduction is absent in this group therefore, diplophase is also absent.

Q.49. Assertion: Rhizopus and Mucor are used in liquor industry.
Reason: These cause fermentation.

Answer Answer: (a) Both Rhizopus and Mucor species are used in alcoholic fermentation. Both of these produce a number of organic acids like citric acid, lactic acid and fumaric acid.

Q.50. Assertion: Morels and Truffles are edible fungi.
Reason: Ascocarps are edible.

Answer Answer: (a) The frutifications of some ascomycetes, i.e., ascocarps are edible, e.g., morels, truffles.

Q.51. Assertion: Yeast are the best source of vitamin B complex.
Reason: Ashbya gossypii is a filamentous yeast.

Answer Answer: (b) Yeasts are the best sources of vitamin B complex. Riboflavin (B6) is obtained from a filamentaous yeast, Ashbya gossypii.

Q.52. Assertion: Claviceps produces lysergic acid.
Reason: It is carcinogenic.

Answer Answer: (c) A derivative of ergot known by name of lysergic acid (LSD) is used in experimental psychiatry, as it is a hallucinogen.

Q.53. Assertion: Mushrooms are called fairy rings.
Reason: Mushroom consists of two parts-stipe and pileus.

Answer Answer: (b) The basidiocarps or mushrooms often lie in rings. Therefore, these are also known as fairy rings. Each basidiocarp consists of two parts-stipe and pileus. The stipe or stalk is fleshy while, pileus is umbrella-like cap of the mushroom.

Q.54. Assertion: Actinomycetes are mycelial bacteria.
Reason: They are called ray fungi.

Answer Answer: (a) Actinomycetes are mycelial (aseptate, branched filamentous) bacteria which form radiating colonies in culture hence, formerly called ray fungi. e.g. Streptomyces.

Q.55. Assertion : Symbiosis is furnished by mycorrhiza.
Reason : In mycorrhiza, symbiosis is established between fungus and alga.

Answer Answer: (c) Mycorrhiza represents mutualistic symbiosis between fungus and roots of higher plants. Fungus helps in absorption of minerals and water more efficiently and protect plant roots from infection. Fungus also gets food from plant.

Q.56. Assertion: Viruses are nucleoproteins and lack cell organelle, etc.
Reason: Viruses are not considered organism.

Answer Answer: (a) Virus is a small infectious agent that can only replicate inside the cells of another organism. Viruses are not considered as organisms as they have no independent machinery.

Q.57. Assertion : TMV is a virus which causes mosaic disease.
Reason : TMV has RNA as genetic material.

Answer Answer: (b) In TMV, the chromosome consists of single stranded, linear RNA molecule coiled into a regular spiral. TMV causes mosaic disease in tobacco and some other plants.

Q.58. Assertion: Mycoplasmas are pathogenic in animals and plants.
Reason: Mycoplasmas lack cell wall and can survive without oxygen.

Answer Answer: (b) Mycoplasmas or mollicutes are the simplest and the smallest of free living prokaryotes, they can survive without oxygen. Mycoplasmas are heterotrophic in their nutrition. Some of them live as saprophytes but majority parasitise plants and animals. The parasitic habit is due to the inability of the most mycoplasmas to synthesise the required growth factors.

Q.59. Assertion: “Contagium Vivum Pasteur Fluidum” was coined by Pasteur.
Reason: Pasteur found that virus infected plant of tobacco can cause infection in healthy plant.

Answer Answer: (d) M.W. Beijerinek (1898) demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants and called the fluid as Contagium Vivum Fluidum (infectious living fluid).

Q.60. Assertion: Virus is an obligate parasite.
Reason: Virus is host specific.

Answer Answer: (b) Virus is an obligate parasite. It is inert outside the host cell. A virus does not grow, divide or reproduce like typical organisms. Instead it multiplies by independent formation of its parts using host cell’s machinery and then assembly of parts to produce virus particles. Viruses are host specific.

Q.61. Assertion: In lichens, mycobiont and phycobiont are symbiotically associated in algae which is predominant and fungi is a subordinate partner.
Reason: In this symbiotic association, the fungus provides food while the alga protects fungus from unfavourable conditions.

Answer Answer: (d) Lichens are symbiotic associations i.e., mutually useful associations between algae and fungi. The algal component is known as phycobiont and fungal component as mycobiont, which are autotrophic and heterotrophic, respectively. Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner. Fungi dominate the relationship.

Q.62. Assertion: These lichens are upright and have pendulous organisation and are attached to substratum by a discoid structure.
Reason: Fruticose are well branched leafy lichens.

Answer Answer: (c) Fruticose are well branched shruby lichens with upright and pendulous organization. These are attached to substratum by a discoid structure. Plant body can be divided into prostrate, leafy and lobed thallus.

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