Rhizobium, found in the root nodules of leguminous plants, is an
Answer: C
Correct answer: Atmospheric Nitrogen fixer
Rhizobium converts atmospheric N2 into ammonia the plant can use, in exchange for sugars. Neither carbon nor oxygen is “fixed” by it - carbon fixation is photosynthesis, and oxygen is not fixed at all.
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Examples of multicellular microorganisms are
Answer: D
Correct answer: Algae and Fungi
Algae and fungi include many multicellular forms - filamentous algae such as Spirogyra, and the mycelia of moulds and mushrooms. Bacteria are always unicellular, and viruses are not cells at all.
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Microorganisms are
Answer: B
Correct answer: Both
Microorganisms are simply organisms too small to see with the naked eye, and that includes both kinds. Most - bacteria, protozoa, yeasts - are unicellular, but many moulds and algae are multicellular, with filaments of many cells. Size, not cell number, is what defines the category.
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A plant disease called citrus canker is caused by a _________ .
Answer: A
Correct answer: Bacteria
Citrus canker is caused by the bacterium Xanthomonas citri. It produces raised corky lesions on leaves, stems and fruit, spreads in wind-driven rain, and is controlled by removing infected trees and by copper sprays rather than by any cure.
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Which of the following drugs is an antipyretic?
Answer: D
Correct answer: Paracetamol
An antipyretic reduces fever, and paracetamol is the commonest - it acts on the hypothalamic centre that sets body temperature. Insulin controls blood glucose and streptomycin is an antibiotic.
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The amount of nitrogen in the atmosphere is
Answer: C
Correct answer: 78%
Air is about 78% nitrogen and 21% oxygen, with argon and carbon dioxide making up most of the rest. Nitrogen is so abundant and so unreactive - the triple bond takes a great deal of energy to break - that living things depend on nitrogen-fixing bacteria to make any use of it.
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The sole members of the kingdom Monera are
Answer: D
Correct answer: Bacteria
Monera is the kingdom of prokaryotes - the bacteria, including the cyanobacteria. It is defined by the absence of a nucleus and of membrane-bound organelles. Mushrooms are fungi, algae are protists or plants, and viruses are not placed in any kingdom, being non-cellular.
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Which of the following is the smallest?
Answer: B
Correct answer: Virus
Viruses are the smallest, typically 20-300 nanometres - far below the resolution of a light microscope, which is why they were unknown until the electron microscope. Bacteria are measured in micrometres, a thousand times larger, and fungi larger still.
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Which of these is a saprotroph?
Answer: C
Correct answer: Fungi
Fungi are saprotrophs: they secrete enzymes onto dead organic matter and absorb the digested products. The pitcher plant is an insectivorous autotroph, and Cuscuta is a parasite that feeds on a living host.
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