Microorganisms
11 Grade 10 General Science questions on Microorganisms, with worked marking schemes. 11 questions are available on this topic in full.
Question 1
1 markA school health club is preparing a poster that groups infections according to the microorganism that causes them. Which list contains only infections caused by viruses?
A. Cholera, typhoid and tuberculosis
B. Measles, tuberculosis and polio
C. Measles, mumps and chickenpox
D. Ringworm, thrush and influenza
(1 mark)
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6 marksDraw a table to compare fungi, bacteria and viruses under the following two features: - presence of a true nucleus - ability to reproduce outside a living host cell (6 marks)
(6 marks)
Marking scheme
1 mark for each correctly completed cell (6 marks). Answers must be presented in a table. - Fungi, true nucleus: present (nucleus enclosed by a nuclear membrane) (1 mark) - Fungi, reproduction outside a host cell: able to reproduce, e.g. on bread, soil or dead matter (1 mark) - Bacteria, true nucleus: absent; genetic material lies free in the cytoplasm (1 mark) - Bacteria, reproduction outside a host cell: able to reproduce, e.g. in milk, water or soil (1 mark) - Viruses, true nucleus: absent; they are not cells and have genetic material enclosed in a protein coat (1 mark) - Viruses, reproduction outside a host cell: unable; they reproduce only inside living host cells (1 mark)
Question 3
1 markMeasles is caused by a virus that spreads through droplets from an infected person's coughs and sneezes, and it mainly affects young children. Which measure would best protect the children of a village from future measles outbreaks?
A. Boiling all drinking water before giving it to children
B. Giving children antibiotics whenever they have a fever
C. Draining stagnant water around homesteads
D. Immunising all infants with the measles vaccine
(1 mark)
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4 marksA county public health officer states that the method used to control an infection must match the way the microorganism that causes it spreads. Using the following infections, justify this statement by stating the mode of transmission and a control measure that targets it.
(a) Tuberculosis (2 marks)
(b) Typhoid (2 marks)
(4 marks)
Marking scheme
(a) Tuberculosis (2 marks): - Mode: airborne, through droplets released when an infected person coughs, sneezes, talks or spits (1 mark) - Matching measure, any one (1 mark): good ventilation of rooms / classrooms / matatus; covering the mouth and nose when coughing; wearing face masks; avoiding spitting in public places; early diagnosis, isolation and full treatment of patients (b) Typhoid (2 marks): - Mode: faecal-oral, through food or water contaminated with faeces of an infected person or carrier (1 mark) - Matching measure, any one (1 mark): boiling or chlorinating drinking water; proper use of latrines / safe sewage disposal; washing hands with soap after visiting the toilet and before handling food; proper food hygiene / covering food; screening and treating food handlers Note: a measure earns the mark only if it blocks the stated route. Vaccination (BCG, typhoid vaccine) protects the individual but does not block the route, so it does not earn the mark here.
Question 5
3 marksState how each of the following microorganisms is transmitted to a human being.
(a) The influenza virus (1 mark)
(b) The human immunodeficiency virus (HIV) (1 mark)
(c) The bacterium that causes tetanus (1 mark)
(3 marks)
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1 markA baker in Eldoret mixes flour, sugar, water and a small amount of a microorganism, then leaves the dough in a warm place for one hour before baking. The dough rises to almost twice its size. Which statement correctly explains the role of the microorganism?
A. Yeast ferments the sugar, releasing carbon dioxide that raises the dough
B. Yeast photosynthesises in the warmth, releasing oxygen into the dough
C. Mould digests the flour proteins, releasing ammonia gas that raises the dough
D. Bacteria turn the sugar into lactic acid gas that raises the dough
(1 mark)
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1 markWhile examining ugali left in a covered sufuria for four days, a Grade 10 learner used a hand lens to observe a cotton-like mass of thread-like structures topped with tiny black round heads. To which group of microorganisms does this growth belong?
A. Viruses, which multiply on moist food surfaces
B. Bacteria, which form long chains of rod cells
C. Algae, which form threads containing chloroplasts
D. Fungi, which grow as hyphae bearing spore cases
(1 mark)
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4 marksAs part of a community service learning project, Grade 10 learners in Kisumu are sensitising traders and households on the significance of food preservation. Explain how each of the following methods prevents the spoilage of food by microorganisms.
(a) Sun-drying omena (2 marks)
(b) Pasteurising fresh milk and packing it in sealed packets (2 marks)
(4 marks)
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4 marksMicroorganisms can both earn and cost a mixed farmer in Kiambu County money.
(a) Outline two ways in which microorganisms are economically beneficial to the farmer. (2 marks)
(b) Outline two ways in which microorganisms cause economic losses to the farmer. (2 marks)
(4 marks)
Marking scheme
(a) Any two of the following, 1 mark each (2 marks): - Nitrogen-fixing bacteria (Rhizobium) in root nodules of beans and other legumes enrich the soil, reducing the cost of fertiliser - Decomposers break down manure and crop remains into compost / humus that improves soil fertility - Bacteria in a biogas digester break down cow dung to produce biogas for cooking and lighting - Bacteria ferment fodder into silage for feeding livestock in the dry season - Microorganisms in the rumen of cattle digest cellulose, allowing cattle to use grass - Bacteria ferment milk into mala / yoghurt that can be sold at a higher price (b) Any two of the following, 1 mark each (2 marks): - Cause crop diseases that lower yields, e.g. maize lethal necrosis (virus), coffee berry disease (fungus), bacterial wilt - Cause livestock diseases, e.g. foot-and-mouth disease (virus), anthrax (bacterium), mastitis, raising treatment costs and causing deaths - Spoil milk, vegetables and other produce before sale - Moulds in poorly stored maize produce aflatoxins, making the grain unfit for sale or use - Cause illness in the farmer and workers, reducing labour and raising medical costs
Question 10
5 marksSeveral learners in a boarding school complain of itching, cracked and peeling skin between their toes. The school nurse notes that the learners share bathroom slippers and that the shower floors are always wet.
(a) Name the infection the learners are most likely suffering from and the type of microorganism that causes it. (2 marks)
(b) Outline three measures the school can take to control the spread of this infection. (3 marks)
(5 marks)
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Create a free account to see itQuestion 11
1 markAfter heavy floods in a lakeside town, pit latrines overflowed into the stream that residents use for drinking water. Within a week, many people developed severe watery diarrhoea caused by the bacterium Vibrio cholerae. Which mode of transmission best explains this outbreak?
A. Inhaling droplets released when patients sneeze
B. Skin contact with soil carried by the floods
C. Bites from mosquitoes breeding in flood water
D. Drinking water contaminated with faecal matter
(1 mark)
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