Topic 4 Longer Response Exam Questions

Q1.
 
The Iberian lynx, Lynx pardinus, is very rare. The wild population consists of less than 200 individuals.

The Iberian lynx and the Eurasian lynx are both found in Spain. The Iberian lynx inhabits open scrubland and the Eurasian lynx inhabits forests.
The Iberian lynx is smaller than the Eurasian lynx and it hunts smaller animals, such as rabbits.
(i)  Explain why the Iberian lynx is not in competition with the Eurasian lynx.
(2)
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(ii)  The Iberian lynx has low genetic diversity.
Evidence from lynx fossils shows little change in the genetic diversity over the past 50 000 years.
Discuss the potential of a captive breeding programme to conserve the Iberian lynx.
(5)
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Q2.
 
Photosynthesis is a process that occurs in all green plants.
Describe how starch is formed from the products of the light-independent reactions of photosynthesis.
(4)
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(Total for question = 4 marks)

Q3.
 
Sloths are mammals found in Central and South America.
The map shows the distribution of two species of sloth. 
There are currently two major populations of C. hoffmanni in South America. 
B. pygmaeus is restricted to an island off the coast of Central America. 
Each population occupies different habitats.

Discuss why the number of sloth species may change in the future.
(6)
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(Total for question = 6 marks)

Q4.
 
The modern bread wheat plant (Triticum aestivum) has been developed from other plant species that have different genomes.
Three species of plant and their genomes are shown in the images.

The diagram shows how chromosomes from different species have combined to produce the bread wheat species used to produce flour.

* New varieties of plants with desirable combinations of characteristics can be produced using the methods shown in the table.

Evaluate the risks and benefits of producing varieties of plants using these methods.
(6)
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(Total for question = 6 marks)

Q1.
No Examiner's Report available for this question

Q2.
 
Many candidates ignored the reference to 'products of the ...' in the question. As a result, many produced a complete description of photosynthesis or the Krebs cycle before then answering the question. Even so many candidates scored well on this question.

Results Plus: Examiner Comments
A clear response that addresses the question directly and gains all four marks.

Results Plus: Examiner Comments
The candidate has not described the formation of glucose from two GALP so did not get marking point one. The response did gain marking point 3 and 4. Although not relevant to the marks awarded, it is worth noting that if they had suggested two GALP form beta glucose, then since starch is formed from alpha glucose they would not have been awarded MP1.

Results Plus: Examiner Tip
Much of the biochemistry needed for A level biology may be taught early in the course. Make sure you learn this biochemistry well. Poor recall of the basic biochemistry (e.g. confusing alpha and beta glucose, or bases and amino acids, or the types of bonds involved in forming biological molecules) is a common reason for candidates to lose marks.

 

Q3.
 
This level based question provided a range of respsonses although there were a majority who only reached level one.
Many candidates did not make reference to a change in the number of species only referring to increased or decreased population.
Other reasons for lower scores included general references to speciation or simply natural selection without any reference to either species referred to in the question.
The strongest responses referred to mechanisms leading to the extinction of Bradypus pygmaeus and evolution of Choloepus hoffmanni due to natural selection to a new species.

Q4.
 
This was the second of the two extended writing questions set in this paper: another one where the command word was 'evaluate', although in this case it was to consider the risks and benefits of three methods described for producing new varieties of plants. Information was provided in the table to provide context to the question.
Most candidates achieved 2-4 marks for this question, with fewer at the extremes, demonstrating a normal distribution of marks – which is to be expected for this type of question, which discriminates well.
There were some good answers, although others were vague or contained incorrect facts. While many candidates made a reasonable attempt to describe the benefits and risks of the three methods, they were not always very clear on either which risk and benefit related to which approach or what the actual risks and benefits were.
Many mentioned infertility or expense, which are drawbacks rather than risks, indicating that they had not read the question carefully or did not understand what is meant by 'risk'.
Many candidates described 'disadvantages' as opposed to risks.
Many seemed to be under the impression that GM held risks of 'unknown side-effects' or some kind of ethical conundrum.
In general, there seemed to be a very poor understanding of genetic modification, with many of the opinion that GM as a process was unpredictable, potentially spreading various resistances to random other plants, bacteria, insects and even humans. Few drew solid conclusions. Many candidates wasted time repeating information on the benefits that they had been given in the table without revealing anything new at all.
A lack of precise details and accurate biology prevented candidates achieving more than Level 2; this included vague references to risks such as 'super weeds' – often in the context of all three methods – without describing gene transfer or interbreeding. The better responses did refer to the risks of antibiotic resistance and had a clear idea of what could be achieved with each method, they also often referred to the risks of inbreeding and loss of alleles with selective breeding.
Statements made were frequently vague, plain wrong, irrelevant or out of context: for example attributing risks to the wrong method. Answers did repeat a host of scare stories about GM which even A-Level biologists seem to have absorbed, with references to 'natural' and 'unnatural'.

Results Plus: Examiner Comments
This is a Level 1 response to this question. Only one side of the argument – the benefits – has been covered. The risks have not been discussed, instead there has been a description of either disadvantages or vague statements including: cost, some plants cannot form hybrids, the long term implications of GM are unknown, selective breeding may result in infertile plants (valid for hybrids, but not for selective breeding).
The benefits for hybridisation were discussed sufficiently to gain the highest mark available at Level 1.

Results Plus: Examiner Tip
If the question asks for risks and benefits to be evaluated, make sure that the risks are not just disadvantages – there is a difference.
e.g. selective breeding takes a long time = disadvantage, but selective breeding may lead to loss of genetic diversity = risk.

Results Plus: Examiner Comments
This is a Level 3 response that gained 5/6 marks.
The risks of each method are described well, with relevant details, including hybrids interbreeding with weeds, making them difficult to control, selective breeding reducing the gene pool and GM risking the introduction of unwanted characteristics to food crops. However, the benefits were not discussed as fully, limiting this response to 5 marks instead of 6.

 

Mark Scheme

Q1.

 

Q2.

 

Q3.

 

Q4.