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 the reason is the correct explanation of assertion.
(b) If both assertion and reason are true but the reason is not the correct explanation of assertion.
(c) If the assertion is true but the reason is false.
(d) If the assertion is false but the reason is true.
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Assertion: Two kingdom classification was insufficient.
Reason: Majority of organisms did not fall into either of the categories in two kingdom classification.
(a) Two kingdom classification (founded by Linnaeus) worked well for a long time. But this system did not 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.
Assertion: Archaebacteria are able to survive in harsh habitats.
Reason: The presence of peptidoglycan in cell wall help archaebacteria to survive in extreme conditions.
(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 the absence of peptidoglycan in their cell walls. Instead cell wall contains protein and non-cellulosic polysaccharide.
Assertion: Methanogens are present in the gut of several ruminant animals.
Reason: Methanogens help in the production of methane from the dung of ruminants.
(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 they help in the production of methane from the dung of these animals. These archaebacteria are helpful to the ruminants in the fermentation of cellulose.
Assertion: Cyanobacteria are photosynthetic autotrophs.
Reason: Cyanobacteria have chlorophyll \(a\) and \(b\) similar to green plants.
(c) Cyanobacteria (also referred to as blue-green algae) are photosynthetic autotrophs. They have chlorophyll similar to green plants.
Assertion: Chemosynthetic autotrophic bacteria oxidise various inorganic substances.
Reason: Energy released during oxidation is used in ATP production.
(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.
Assertion: Mycoplasmas are pathogenic in animals and plants.
Reason: Mycoplasmas lack cell wall and can survive without oxygen.
(b) Almost all of the Mycoplasmas are pathogenic in animals and plants. Mycoplasma can infect animal and plant cells because of its adhering ability. They do lack cell wall and can survive. But, this is not the reason for its pathogenicity.
Therefore both the assertion and reason are true but the reason is not the correct explanation of the assertion.
Assertion: Cell wall of Chrysophytes are indestructible.
Reason: Cell wall of Chrysophytes have layer of magnesium pectate embedded in it.
(c) Chrysophytes include diatoms and golden algae (desmids). They are found in freshwater as well as in marine environments. The cell walls are embedded with silica and thus the walls are indestructible.
Assertion: Euglena is called a plant-animal.
Reason: Pellicle of Euglena is made up of cellulose and not protein.
(c) Euglena is studied as plant as well as animal. It is called plant-animal. Plant characters of Euglena are the presence of chloroplasts with chlorophyll and holophytic (photosynthetic) nutrition in presence of light. Animal characters of Euglena are the 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.
Assertion: The protoplasm of plasmodial slime mould is considered the purest in the world.
Reason: Protoplasm of plasmodium is differentiated into an outer enucleated and central nucleated portions.
(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.
Assertion: Sporozoans may have silica shells on their surface.
Reason: Sporozoans are endoparasites.
(d) Sporozoans are endoparasites. The body is covered with an elastic pellicle or cuticle.
Assertion: Phycomycetes are commonly known as sacfungi.
Reason: In Phycomycetes, zoospores or aplanospores are produced endogenously in sporangium.
(d) Ascomycetes is commonly known as sac-fungi.
Assertion: Deuteromycetes is known as fungi imperfecti.
Reason: In Deuteromycetes, only the asexual phase is known.
(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.
Assertion: Pasteur coined Contagium Vivum Fluidum.
Reason: M.W. Beijerinck found that virus-infected plant of tobacco can cause infection in healthy plants.
(d) M. W. Beijerinck demonstrated that the extract of the infected plant of tobacco could cause infection in healthy plants and called the fluid Contagium Vivum Fluidum (infectious healthy fluid).
Assertion: Virus is an obligate parasite.
Reason: Virus is host specific.
(b) Virus is an obligate parasite. It is inert outside the host cell. A virus does not grow, divide, or reproduce like typical organism. Instead, it multiplies by the independent formation of its parts using host machinery and then assembly of parts to produce virus particles. Viruses are host specific.
Assertion: In lichens, mycobiont and phycobiont are symbiotically associated in which algae is predominant and fungi is a subordinate partner.
Reason: The alga provides food and fungus provides shelter and absorb mineral nutrients and water for the alga.
(d) A lichen is an organism that results from a mutualistic relationship between a fungus and an alga. The fungus grows around the algal cells. The fungus benefits from the constant supply of food produced by the photosynthesizer algal part. The photosynthesizer benefits from the water and nutrients absorbed by the fungus.
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