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AS Science in Society – Answers to revision questions
Answers to revision questions
Suggested answers are given in italics. Each bullet point represents one point
for one mark. Where several points are given these are alternatives. The
examiners comments are given below the bullet points in normal type.
3.1.1 Germ theory of disease and 3.1.2 Infectious
disease
1. Comments by an examiner on how to rewrite the statements so that they
will get marks.
a) Bacteria can become resistant to antibiotics if they are exposed too often.
Bacteria do not have an immune system. Antibiotics do not change
individual bacteria, they select for the most resistant in the population.
b) True for antibodies which help prevent disease as part of the immune
system. Not true for antibiotics which cure some diseases.
c) Better housing helps prevent airborne and water borne infectious
diseases.
d) Antibiotics only cure the infectious diseases that are caused by bacteria,
They have no effect on viruses.
e) Nothing is completely safe. We should make sure that they are as safe
as possible. Vaccines are much safer than the disease they prevent.
f)
The most significant difference between viruses and bacteria is that
viruses are not independent living organisms. They have to live inside a
cell and use the cell processes to reproduce.
g)
All of the following diseases can be prevented by immunisation; measles,
smallpox, TB, hepatitis. There are still no vaccines for HIV and malaria .
h) The following diseases can be prevented by clean water; cholera,
hepatitis, dysentery. Chickenpox, anthrax and TB are not waterborne .
2. a)
 No change between 1994 and 1998.
 Decline from 2000 to 2006.
 May have levelled out again from 2006
You will get a mark for each of the points above. Note that you must describe
the different periods separately and give dates. A general ‘deaths have gone
down’ would not score marks.
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b) 1994
The range of uncertainty is 55 in this year. Subtract the lowest possible
value from the highest possible value to find the range within which the
rue value is expected to lie.
c)
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

The ranges of uncertainty for the two years overlap.
the range indicates that it is known that the 2004 value is between 32
and 60, which includes the 2006 value of 37
2006 range of 24 – 52, includes the 2004 value of 45
Any 2 points
d)



War
poor health services / lack of accurate diagnosis
poor transport links
3.1.3 Transport issues
1. a)
 different chemical elements
 combined in a fixed ratio
The terms element and fixed ratio are both essential here. Make sure you
understand the difference between a mixture which can have different
substances in any proportion. A compound always has the same
elements in the same ratio. If the ratios are different it is a different
compound.
b) Hydrocarbon + oxygen
carbon dioxide + water
You must include the oxygen, without it there is no reaction.
2. a) 11.2 x100 = 32%
35
Remember the starting value, in this case the energy of petrol itself, goes on
the bottom.
b)
 It is released as heat
 It heats the air/ the car/ the road
Remember energy is not destroyed it is just spread out.
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3. a) Athens, London, Barcelona, Birmingham
Confidence interval depends on the spread of values. It tells us that there is a
95% probability that the true value of the mean lies within these limits.
For all of these the confidence interval (could call it error bar) does not extend
past 0. There is a 95% probability that the true mean is >0.
b) The confidence interval includes negative values although the mean is
greater than 0. There is therefore a probability that the true mean is
negative, the death rate could actually decrease.
c)




Other pollutants could have a strong effect on death rate
the data from the pollution monitoring stations may not be accurate
health data may not be accurate
the ozone level may always be very high so an increase of 10μg/m3
would have less effect
d) No. We have a correlation but we need a causative mechanism to
conclude causation.
e)


wider range of data
smaller sample size
3.1.4 Medicines and 3.1.5 Ethical issues in medicine
1. a)
 the patients do not know which group they are in
 the medical staff do not know which patient is in which group
Of course a controller who is not involved with the patients in any way knows
who is in which group
b)


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it reduces the effect of patient expectations on the reported outcome
it prevents the expectations of medical staff influencing the way they
treat patients
the placebo effect is the same for both groups so the difference is likely
to be due to the drug
There is no placebo in this trial but patient expectations on which drug is
better could still affect their outcomes in a way similar to the placebo effect.
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c)
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

it is important that the two groups are as equal as possible, on
average, apart from the different drugs
we do not know all the other variables that might be important
randomly selected groups are likely to be matched on other variables.
medical staff might make choices based on some patient characteristic
for example they might think the new drug is better and put the patients
who are worse into that group/ or do the opposite
It is very rare for researchers to assign patients to groups on the basis on
known variables. Any matching is likely to introduce bias.
d)
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
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high blood pressure is known as a significant risk factor
it would be unethical to deny patients treatment that is known to be
effective
patients in the trial would be worse off than normal patients if they were
given placebo
trials may do harm because of unknown risks but it is unethical to
cause known risks
e) the risk of high blood pressure is so great, death or disability from stroke
or heart attack, that the benefit of reducing it outweighs the discomfort of
the side effects.
f)
g)
h)
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
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negative results are as useful as positive ones
it helps doctors know what to prescribe
It might be tempting to assume that a new drug is better
if it is not published others will not know the outcome and do the work
again which would be a waste of resources


a larger sample size means that the results are less likely to be due to
chance
in a small sample a result might be due to random variation in the
groups

larger SD means a greater spread of ages in the group
You do not need to know how a SD is calculated but you do need to be able
to recognise it ‘as an indication of the spread of values’
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3. 1.6 Reproductive choices
1.
a) Humans have about 30 000 genes.
There are only 46 chromosomes each containing many genes
b) Most diseases are caused by environmental factors though a few
inherited diseases such as sickle cell or cystic fibrosis are caused by the
genes we inherit.
c)
A mutation is change to a gene.
Not all changes are harmful. Evolution would not happen without
mutation.
d) If both parents carry a single gene/allele with a mutation for a genetic
disease the chance of each of their children inheriting the disease is 1 in 4
if the allele is recessive. If it is dominant then the risk is 1 in 2.
e) The term ‘designer baby’ means a baby that has been conceived by IVF
with the characteristics that the parents want. This is what the term
means but designer babies are still in the realm of science fiction. It is not
possible to choose which of the parents’ genes a baby receives or even to
test for the genes for many characteristics.
f)
PGD and IVF are not different terms for the same technique.
PGD can only be done on an embryo conceived by IVF but most IVF
embryos are not tested using PGD.
g) IVF can be used to prevent the birth of babies with genetic diseases if the
IVF embryo is then tested using PGD and embryos carrying alleles for a
disease are then discarded .
h) PGD can be used to identify an embryo with a genetic disease.
It is not possible to use gene therapy on an embryo. Embryos found to be
carrying a disease are discarded and only those without the disease
alleles are implanted.
i)
Preimplantation genetic diagnosis, PGD, means that the egg and sperm
are tested before conception. This is wrong. If the genes in an egg or
sperm were tested they would be destroyed in the test. PGD takes one
cell from a developing embryo, which does not affect the development.
j)
Amniocentesis can be used to prevent the birth of a baby with a genetic
disease if it is followed by abortion of the affected fetus.
Amioncentesis itself identifies the affected fetus. The parents then have
to decide whether to have an abortion.
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2. A
a) Use a utilitarian argument, the harm to the family from long term caring
and the possible suffering of the disabled child could outweigh the harm of
the abortion.
b) The mother’s autonomy is important here. The mother may have a strong
belief in the right to life and would refuse an abortion even if the child did
have Down syndrome.
c) This would involve the ill child’s right to life or a utilitarian argument for
overall benefit.
d) They could use a utilitarian argument to defend their restriction. IVF is
expensive and the same money could pay to help a greater number of
people with other health problems.
2.B
a) The foetus’ right to life
b) If the mother is considered as making the decision on her own behalf the
only way to argue against her autonomy would be by using a utilitarian
argument about the difficulty of bringing up a handicapped child.
However she is in effect also making a decision on behalf of the unborn
child. Again hard to argue against its existence.
c) The child they wish to conceive is being used as a means to an end. It
goes against the autonomy of this child as a person in its own right.
d) This decision does not ensure justice, couples who can afford to will be
able to pay for several rounds of IVF and greatly increase their chance of
having a child. It is not justice if some couples are unable to have
children because they cannot afford the medical treatment they need.
3.1.7 Radiation
a) More neutrons
b) same number of protons
c) 2 half lives
60 years
d) isotopes taken up by plants/small creatures in sea
eaten by fish
fish contaminated with radioactive isotopes
long half life means isotopes remain in food chain
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e) radiation/ βemissions
cause mutations in DNA
cells reproduce uncontrollably
f)
Sieverts measure the amount of damage to the body
different types of radiation cause different amounts of damage
g) 20 in 20 000 cases
1 in 1000 risk
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