Viruses, Bacteria and Fungi

1. INTERACTIVE MULTIPLE CHOICE QUESTIONS Viruses, Bacteria and Fungi The answers are provided. Explanations of why the alternatives are unsatisfactory are also offered

2. These multiple choice questions are similar to the ones set by the GCSE and IGCSE Examination Boards except that, in some cases, there may be more than one acceptable answer. For this reason, even if you select a correct answer at your first attempt, it is worth looking at all the alternatives (a) to see if there is a better answer and (b) to see why some of the alternatives are unacceptable. First slide

3. Question 1 Which of the following are characteristics of a virus? (a) Respiration (b) Growth (c) Excretion (d) Reproduction Question 2

4. No Viruses do not respire

5. No Viruses do not grow but they do reassemble themselves in the host’s cell

6. No Viruses do not excrete

7. Yes Viruses do reproduce inside the host’s cell. Their DNA (or RNA) replicates and they assemble new protein coats using the host’s resources

8. Question 2 Viruses can reproduce only… (a) at certain temperatures (b) inside a living cell (c) in dry conditions (d) inside bacteria Question 3

9. No Reproduction of viruses is not dependent on temperature. They will produce at any temperature which does not damage their host’s cells

10. Yes Viruses can reproduce only in the cells of their host organism

11. No Unless the host is harmed by dry conditions, the virus reproduces in the cytoplasm of the host’s cells

12. No There are certain viruses, called bacteriophages, which reproduce inside bacteria but this does not apply to all viruses

13. Question 3 Which of the following diseases is caused by a virus? (a) Influenza (b) Tuberculosis (c) Syphilis (d) Sore throat Question 4

14. Yes Influenza (‘flu’) is caused by a virus

15. No Tuberculosis is caused by a bacterium, Mycobacterium tuberculosis

16. No Syphilis is caused by a spirochaete bacterium, Treponema pallidum

17. No Sore throat is caused by a Streptococcus bacterium.

18. Question 4 A bacterial cell differs from a plant cell by having … (a) no cell wall (b) no central vacuole (c) no nuclear membrane (d) no cytoplasm Question 5

19. No A bacterial cell does have a cell wall but, unlike a plant cell wall, it does not contain cellulose

20. Yes A bacterial cell has no central vacuole

21. Yes A bacterial cell has no nuclear membrane

22. No A bacterial cell does have cytoplasm

23. Question 5 Most bacteria can be killed by … (a) cooking (b) refrigeration (c) freezing (d) canning Question 6

24. Yes (within limits) If the temperature is high enough and the cooking reasonably prolonged, the majority of bacteria will be killed. There will probably be a residual population of bacteria but not in sufficient numbers to cause disease. However, if the cooked food is left at room temperature, this small population will multiply rapidly

25. No Refrigeration at 4oC does not kill bacteria but slows down their rate of reproduction so that the food remains safe for longer periods

26. No Freezing at about minus 18oC stops bacteria from reproducing but does not kill them

27. Yes Food is canned at high temperatures and pressures to kill bacteria

28. Question 6 Which of the following is a bacterium? (a) Penicillium notatum (b) Candida albicans (c) Plasmodium vivax (d) Salmonella typhimurium Question 7

29. No Penicillium notatum is a mould fungus. It grows on decaying fruit and other organic matter and is the source of the antibiotic, Penicillin

30. No Candida albicans is a yeast-like fungus. It causes a disease called ‘thrush’

31. No Plasmodium vivax is a protozoan parasite which causes malaria

32. Yes Salmonella typhimurium is a bacterium which causes one form of food poisoning

33. Question 7 Which of the following diseases is caused by bacteria? (a) Tinea (b) The common cold (c) Typhoid fever (d) Diabetes Question 8

34. No Tinea is a skin infection caused by one of a number of fungal parasites which cause inflammation between the toes (‘athletes’ foot’), on the scalp or in the pubic region

35. No The common cold is caused by a virus, (a ‘rhinovirus’).

36. Yes Typhoid fever is caused by a bacterium, Salmonella typhi.

37. No Diabetes is not an infectious disease. It arises as a result of either (a) a failure of the pancreas to produce sufficient insulin or (b) an inability of the body to use insulin effectively

38. Question 8 A fungus is made up of … (a) hyphae (b) cells (c) cytoplasm (d) chitin Question 9

39. Yes Hyphae are the living, thread-like structures which form a fungus

40. No Fungi are made up of hyphae which have a wall, cytoplasm and nuclei like plant cells but are in the form of long threads

41. No A fungus is made up of hyphae which do contain cytoplasm, but the fungus is not made solely of cytoplasm

42. No Chitin is a component of the hyphal wall but the fungus is not made up of chitin

43. Question 9 A The drawing represents a mushroom partly in section. Which of the following structures represents the mycelium? C B soil level (a) A (b) B (c) C D (d) D Question 10

44. No This is the ‘cap’ of the mushroom

45. No These are the ‘gills’ of the mushroom. They carry the spores.

46. No This is the mushroom’s ‘stalk’

47. Yes This network of hyphae constitutes a ‘mycelium’

48. Question 10 Fungi have the potential to produce large numbers of offspring by ... (a) producing many seeds (b) sexual reproduction (c) producing fruits (d) producing many spores

49. No Fungi do not produce seeds

50. No Fungi do have methods of sexual reproduction but they do not result in the production of large numbers of offspring