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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Deliberately injecting weak microbes into a healthy body and producing antibodies to fight against strong microbes is called _______
Answer: C
Correct answer: Vaccination
Vaccination introduces a weakened or killed organism, or a part of one, so that the body mounts a response and retains memory cells. A later encounter with the real pathogen is then met at once. Antibiotics treat an infection already present; a vaccine prevents one.
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Which one of the following is not a beneficial effect of fungi?
Answer: C
Correct answer: They are used to make yoghurt.
Yoghurt is made with bacteria - Lactobacillus and Streptococcus - not with fungi. The other three are genuine benefits: fungi produce antibiotics such as penicillin, they act as decomposers, and they are essential to cheese making.
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Living organisms which are invisible to the naked eye are called _________ .
Answer: C
Correct answer: Microorganisms
Organisms too small to be seen without a microscope are microorganisms - bacteria, protozoa, many algae and fungi, and viruses. The category is defined by size alone, so it contains organisms of quite unrelated kinds.
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The scientist who discovered fermentation is
Answer: B
Correct answer: Louis Pasteur
Louis Pasteur showed in the 1850s that fermentation is caused by living microorganisms, not by a purely chemical process as had been supposed. The same work led to pasteurisation and to the germ theory of disease.
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The shape of a coccus bacterium is generally
Answer: A
Correct answer: Spherical
A coccus is spherical. The other basic shapes are the rod (bacillus), the comma (vibrio) and the helix (spirillum or spirochaete).
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Organisms that take in nutrients from dead and decaying matter are called
Answer: C
Correct answer: Saprotrophs
Saprotrophs feed on dead and decaying matter, secreting enzymes onto it and absorbing the products - the fungi and many bacteria. They are the decomposers, without which nutrients would stay locked in dead material and the cycles of matter would stop.
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Which of these microorganisms contains chlorophyll?
Answer: C
Correct answer: Algae
Algae contain chlorophyll and photosynthesise. Fungi have none - they absorb organic nutrients - and viruses are not cells at all.
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Rhizobium, the organism found in the root nodules of legumes, is a -
Answer: A
Correct answer: Bacteria
Rhizobium is a soil bacterium. It invades the roots of legumes, forms nodules, and fixes atmospheric nitrogen into ammonia the plant can use, taking sugars in return.
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