Which one of the following acts as a decomposer?
Answer: A
Correct answer: Bacteria
Bacteria are the principal decomposers, breaking down dead organic matter and returning nutrients to the soil. (Fungi and moulds do the same work, and are decomposers too - but bacteria are the answer the question is looking for, being the most numerous and the most versatile.)
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Which one of the following statements is incorrect?
Answer: B
Correct answer: Bacteria cannot respire.
That statement is false: bacteria do respire, some aerobically and some anaerobically, and some ferment instead. The others are true - bacteria cause a range of human infections, bacteria are used in cheese making, and soil bacteria decompose dead plants and animals.
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Which of these is an autotroph?
Answer: B
Correct answer: Algae
An autotroph makes its own food, and algae do so by photosynthesis. Mushrooms and most bacteria absorb organic nutrients, and Cuscuta (dodder) is a parasitic plant with almost no chlorophyll, drawing its food from a host.
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Viruses that infect bacteria are called
Answer: D
Correct answer: Bacteriophages
A virus that infects a bacterium is a bacteriophage - literally “bacteria eater”. Phages are the most numerous biological entities on earth, and they are used both as research tools and, increasingly, as an alternative to antibiotics against resistant infections.
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Of all microorganisms, the most adaptable and versatile are the
Answer: B
Correct answer: Bacteria
Bacteria are the most versatile of all organisms: they live from the deep sea to hot springs to the human gut, and among them are found every mode of nutrition - photosynthesis, chemosynthesis, fermentation, respiration on a dozen different acceptors. Their short generation time also lets them adapt genetically with great speed.
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Who discovered the process of fermentation?
Answer: B
Correct answer: Louis Pasteur
Louis Pasteur established in the 1850s that fermentation is the work of living microorganisms rather than a purely chemical change. The same investigations gave us pasteurisation and, in time, the germ theory of disease.
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Which one of the following is not a method of food preservation?
Answer: C
Correct answer: Boiling
Boiling kills the organisms present at the time but leaves the food just as open to recontamination as before, so it preserves nothing by itself. Salting and drying remove the water microbes need, and pickling makes the food too acid for them - each creates conditions in which spoilage organisms cannot grow.
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Fungi are simple plants. Which one of the following statements about fungi is INCORRECT?
Answer: A
Correct answer: Fungi contain chlorophyll.
Fungi have no chlorophyll and cannot photosynthesise - which is why they must absorb organic nutrients, as saprotrophs or as parasites. The absence of chlorophyll is the main reason they are no longer classed as plants at all, but placed in a kingdom of their own.
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An infectious disease is ___________ .
Answer: B
Correct answer: spread from person to person
An infectious (communicable) disease is one that can be transmitted, whether by air, water, contact or a vector. The cause may be a bacterium, a virus, a fungus or a protozoan - it is the transmissibility, not the kind of organism, that defines it.
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Partial sterilization of a product such as milk at a high temperature is known as:
Answer: A
Correct answer: Pasteurization
Pasteurisation heats milk briefly - about 72°C for 15 seconds, then rapid cooling - which kills the pathogens and most spoilage organisms without curdling the milk or spoiling its flavour. It is partial sterilisation: some harmless organisms survive, which is why pasteurised milk still needs refrigeration.
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