Questions

Q1.
 
A pathologist can use a number of methods to estimate the time of death of a body found at a crime scene.
The pathologist will measure the body temperature and the temperature of the surroundings.
Explain why it is necessary to take these two measurements as soon as possible.
(3)
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(Total for question = 3 marks)

Q2.
 
The time of death of a person can be estimated in a number of ways. One method is 
to use a Henssge nomogram.
The Henssge nomogram relates the time of death to the ambient (surrounding) 
temperature, the core temperature and the mass of the body.
Explain why the ambient temperature and the core temperature of the body are 
used to determine the time of death of a person.
(3)
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Q3.
 
* A pathologist can use a number of methods to estimate the time of death of a body found at a crime scene.
A pathologist can also use forensic entomology to estimate the time of death of a body.
The diagram below shows the life cycle of a fly.

Describe an investigation that could be carried out to study the effect of temperature on the time taken for the first instar maggot to become a pupa.
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(Total for question = 5 marks)

Q4.
 
As part of the immune response, a B cell has to be activated. It then divides to form a clone of cells. These cells then differentiate into plasma cells, which produce antibodies.
Describe how a B cell is activated.
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(Total for question = 3 marks)

Q5.
Human diseases can be caused by many different types of organism, such as bacteria and viruses.

(a)  Give two differences between the genetic material of bacteria and viruses.
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(b)  Tuberculosis (TB) is caused when droplets, containing the bacterium Mycobacterium tuberculosis, are inhaled into the lungs.

In the lungs, large numbers of the bacterium are formed rapidly. These can be ingested by macrophages. Eventually, tubercles (tissue masses), containing dormant bacteria inside macrophages, may form.

(i)  Describe how macrophages ingest the bacteria.
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(ii)  Suggest why treatment with antibiotics may not be effective against the dormant bacteria in the tubercles.
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(iii)  TB can be prevented by vaccination. Explain how a person can develop artificial active immunity following vaccination.
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(c)  In a person with TB, the dormant bacteria in tubercles may be activated after several years. The bacteria multiply rapidly, resulting in severe lung damage.

The bacteria are released from the tubercles. These bacteria can inhibit the activity of T cells and infect other organs.

Explain why the activity of these bacteria and the inhibition of T cells means that a person may quickly develop severe symptoms leading to death.
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(Total for Question = 13 marks)

Examiner's Report

Q1.
 
We have asked questions on body temperature and ambient temperature a number of times in the past, but not usually in relation to the importance of taking the readings as soon as possible. Many candidates gave us our first two marking points but far fewer commented on the fact that the ambient temperature alters over time.

Results Plus: Examiner Comments
This is a clear response of the standard that we were hoping for.

Results Plus: Examiner Comments
This response typically gave us the first two points on the mark scheme and in addition our fourth point. A number of candidates who tried to give us point 4 worded it poorly and told us that the readings would be more accurate instead of the time of death.

 

Q2.
 
Another question assessing a familiar part of the specification but again many candidates rushed their response without considering what the third mark could be for. Mark points 1 and 2 were frequently awarded but a more lateral approach was rarely seen.

Results Plus: Examiner Comments
A typical response scoring 2 marks.

Results Plus: Examiner Tip
Do not forget that ambient temperature not only affects the change in temperature of the body but also the rate of decomposition and rigor and the duration of insect life cycles.

 

Q3.
 
Few candidates really thought about the question being asked before launching into their response.
Few picked up the subtlety of the context so mark points 3 and 4 were rare. Those who tried to make mark point 4 usually stated that the second instar maggot turns into the pupa, which is clearly not the case if they looked at the diagram and thought about their answer

Results Plus: Examiner Comments
This candidate was one of the exceptions who did try to answer the question in its context, but we did not like their reference to 'nutrients' being supplied.

Results Plus: Examiner Comments
Candidates have learnt from numerous past paper mark schemes that if temperature is the independent variable then there will be marks for stating that a range of temperatures should be used and that a waterbath is the correct piece of equipment to use. However some thought needs to be given to their answer as stated temperatures have to sensible; we felt that 60°C was just a bit too hot.

 

Q4.
 
We saw some very good descriptions of B cell activation.
Some candidates wrote about the activation of T helper cells and then only commented on the subsequent release of cytokines.

Results Plus: Examiner Comments
This is a very concise account of B cell activation.

Results Plus: Examiner Tip
Activation of B cells, T helper cells and T killer cells involve similar principles but they each involve different modes of antigen presentation.

 

Q5.
Question (a)
The candidates that read the question carefully did reasonably well in that they did not try to write comparisons that did not involve the nucleic acid. However very few scored more than one mark; it appeared that candidates had only been taught the structure of HIV and not viruses in general.

Results Plus: Examiner Comments
A good response where the candidate has tried to make more than the required two comparisons. We usually expect the candidates to make their two comparative statements within the same sentence, but as the candidates did struggle with this question we decided to piece their answers together.

Results Plus: Examiner Tip
Always try to give one more comparison than the question asks.

Question (b)(i)
Not too many problems were encountered here, except by the candidates who simply repeated the question or who gave irrelevant information not relating to the process of phagocytosis itself.

Results Plus: Examiner Comments
This is an example of the type of response that we were looking for.

Results Plus: Examiner Tip
Do not repeat the information given in the question in your answer.

Question (b)(ii)
A slightly more challenging question which again required the candidates not to repeat the information given in the question. Many just stated that the bacteria were inside the tubercles. There was also the expected confusion between antibiotics and antibodies.

Results Plus: Examiner Comments
This example illustrates marking points 1, 2 and 3, in that order.

Results Plus: Examiner Comments
This is very typical of the responses made by the weaker cohort of candidates.

Question (b)(iii)
Candidates made a good attempt at answering this question, but only a small percentage scored full marks. A large percentage described artificial passive immunity. Many wrote clumsy descriptions that were just not accurate enough to award marks at A2. Some churned out past mark schemes that did not quite answer the question.

Results Plus: Examiner Comments
A good response that could be awarded mark points 1, 3, 4 and 6 in that order.

Results Plus: Examiner Comments
This could not be awarded any marks. We cannot award wrong biology – a vaccination does not contain TB – this is the name of the disease and not the bacterium. This was a very common mistake that prevented us awarding the first mark point. The reference to B memory cells is in the wrong context for this question.

Results Plus: Examiner Tip
Although we really want you to use past mark schemes in your preparation for the examinations, we need you to apply them to the context of the question and not just repeat them verbatim to any question on that particular topic.

Question (c)
This question saw a range of responses and discriminated well; the weaker candidates struggled and the better candidates scored well.

Results Plus: Examiner Comments
This is an example of one of the good responses that we saw. Mark points 1, 3, 5, 6, 7, 8, and 4 were all awarded, in that order.

Results Plus: Examiner Comments
Mark points 5, 4 and 8 were awarded on the first couple of lines. Mark point 1 could not be awarded as the candidate did not refer to 'further' damage or 'severe' breathing problems being caused. For mark point 2 we wanted to know how the bacteria travel round the body to the other organs.

Results Plus: Examiner Tip
Read the question very carefully and then apply your knowledge to the question being asked.

Mark Scheme

Q1.

 

Q2.

Q3.

 

Q4.

 

Q5.