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Testbank for PYC 115 pages. Document contains past questions, answers and page references. Can be used to assist students with assignments and examination preparation.
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PYC2605Testbank
,The document contains previous questions with answers, and page references.
Take note: where two-page numbers are provided, e.g., p. 10 / p. 15, the first page number
refers to the 6th edition and the second page number refers to the 5th edition.
,QUESTION 1
What is currently the most widely accepted scientific theory about the origin of Aids?
(1) An ancestor of HIV-1 group M virus was transmitted from a chimpanzee to a hunter.
(2) HIV was introduced into the human population by polio vaccines which were produced on monkey
kidney cell cultures in the 1950s.
(3) Aids is not a new disease, but has probably been present for many centuries in central Africa.
(4) HIV originated in the white gay communities of America and Europe in the early 1980s.
Feedback on Question 1
The correct answer is 1. There are many theories about the origin of Aids. However, the accepted theory
(after doing a scientific process called ‘sequence comparisons’) is that HIV crossed the species barrier from
primates to humans at some time around the 1930s when chimpanzee blood infected a human being.
Alternative 2 is not correct and can be seen as a conspiracy theory (polio vaccines causing Aids).
Conspiracy theories like this do a lot of damage to vaccine programmes and can cost the lives of thousands
of children. Alternative 3 is not correct since HIV is not that old. Alternative 4 is incorrect because,
although HIV was first diagnosed in white, gay men in America, it is not where HIV originated. Read
“Crossing the species barrier” (p. 7) for more information.
QUESTION 2
How do viruses (including HIV) reproduce?
(1) Viruses can reproduce in any warm and humid environment; the cells of the virus divide to form new
viruses.
(2) Viruses reproduce in the open air; they cannot reproduce in anaerobic conditions.
(3) Viruses ‘inject’ their genetic material into a living cell and then use the cell to reproduce more viruses.
(4) Viruses first kill cells, then enter them and then use the remains of the cell as ‘food’ for the new viruses.
, Feedback on Question 2
The correct answer is 3. Viruses need other cells to be able to reproduce. They have to enter cells and take
over the normal mechanisms of the cells to be able to divide and increase their numbers. Therefore,
viruses cannot reproduce in any environment as they need to access other cells in order to multiply using
these host cells abilities to divide. Alternative 1 is more correct for the conditions bacteria need to
reproduce, but it is not true for viruses. Alternative 2 is incorrect (viruses do not reproduce in open air),
and Alternative 4 is wrong because viruses do not kill the host cells to use them as food as they need living
cells in order to facilitate their multiplication. Read page 38 in your prescribed book for more information.
QUESTION 3
The defences of the immune system can be divided into two main groups: the non-specific defences, for
example (a) ____, and the specific defences, for example (b)____.
(1) (a) the skin and mucous membranes; (b) plasma proteins
(2) (a) phagocytes (e.g. macrophages); (b) lymphocytes (e.g. T cells and B cells)
(3) (a) plasma proteins; (b) phagocytes (e.g. macrophages)
(4) (a) T lymphocytes (e.g. CD4+T cells); (b) B lymphocytes (e.g. B memory cells)
Feedback on Question 3
The correct answer is 2. To understand the division of the immune system into non-specific and specific
defences, look at Figure 2.1 on page 27. Although you do not have to study figures, this figure gives a nice
summary of the content under Section 2.1.1 to Section 2.1.3 on pages 29 to 33. Non-specific defences
defend the body in a ‘crude’ manner, which means that they do not have specialised weapons (therefore
the name ‘non-specific’ defences. Non-specific defences consist of two lines of defence. The first line of
defence (physical barriers) tries to keep pathogens out of the body (e.g. the skin and mucous membranes).
The second line of defence is the inflammatory reaction. When the skin breaks and pathogens do enter
they body (e.g. a child falls), protective plasma proteins and cells like phagocytes (e.g. macrophages) try to
get rid of the pathogens by killing or eating them. So far the (a) part of both alternatives 1 and 2 are
correct.
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