AS & A Level Biology - 9700 Paper 4 2010 Winter Zone 2

(a) Using the information in Table 1.1 suggest reasons for the changes in numbers of these birds.

Table 1.1:
[Table_1]

(b) An ecosystem that has a wide range of species has a high biodiversity.
Explain the benefits of maintaining biodiversity.
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(a) Antibiotic A belongs to a group of antibiotics known as anti-pseudomonal penicillins.

(i) Describe the mode of action of penicillin on bacteria.
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(ii) Explain why penicillin does not affect viruses.
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(b) Wild-type and mutant bacteria were grown on solid culture media both with antibiotic \( A \)
and without antibiotic \( A \).

The subsequent change in numbers of living bacteria is shown in Fig. 2.1.



With reference to Fig. 2.1, describe the changes in numbers of the wild-type and mutant bacteria on culture media with antibiotic \( A \) and without antibiotic \( A \).
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(c) The wild-type and mutant strains of this bacterium have different DNA sequences in part of a gene coding for an enzyme which is needed to produce polymers of glucose, called glucans. Glucans are secreted by bacteria and can bind to various molecules, including those of antibiotic \( A \).

Explain

(i) how a mutation of a gene coding for an enzyme may result in an enzyme with reduced activity,
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(ii) the different effects of antibiotic \( A \), shown in Fig. 2.1, on the wild-type and mutant
strains of bacteria.
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(d) Explain the role of natural selection in the evolution of antibiotic resistance in bacteria.
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(a) With reference to Fig. 3.1, explain why women are treated with hormones for two weeks after being given drugs to suppress ovulation at the beginning of IVF treatment.
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(b) State the roles of mitosis and meiosis in producing an immature secondary oocyte.
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(c) Suggest one advantage and one possible disadvantage of fertilising an oocyte by injecting a sperm into its cytoplasm instead of mixing the oocyte with a sample of sperm.

advantage .......................................................................................................
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disadvantage .................................................................................................
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The secretion of insulin by the islets of Langerhans in the pancreas stimulates the liver to reduce the blood glucose concentration.

(a) Describe how the liver reduces blood glucose concentration, when insulin is secreted.
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(b) Almost all insulin used to treat type I diabetes is produced by genetically engineered bacteria or yeast. A summary of this procedure is shown in Fig. 4.1.

[Image_1: Flow chart showing steps from isolating human insulin gene to cloning bacteria and extracting insulin]

(i) One way of carrying out step 1 is to collect mRNA from β cells from the pancreas. The relevant mRNA is then isolated and used to make DNA. Suggest why isolating the mRNA coding for insulin in a β cell is easier than isolating the DNA for insulin in a β cell.
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(ii) Outline the use of restriction enzymes in step 2.
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(c) Most people with type I diabetes inject insulin. A recent product contains insulin that can be administered using a nasal spray. The spray is inhaled and the insulin is taken up through the lungs.

Fig. 4.2 shows the concentration of insulin in the blood plasma in the 480 minutes after injecting or inhaling insulin. In both cases, the insulin was of the same type, obtained from genetically engineered Escherichia coli.

[Image_2: Graph of insulin concentration over time for inhaled vs injected insulin]

Fig. 4.3 shows the concentration of glucose in the blood plasma in the 480 minutes after injecting or inhaling insulin.

[Image_3: Graph of glucose concentration over time for inhaled vs injected insulin]

(i) Compare the results for injected insulin and inhaled insulin shown in Fig. 4.2.
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(ii) With reference to Fig. 4.2, explain the differences in the blood glucose levels after injecting or inhaling insulin shown in Fig. 4.3.
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(iii) With reference to Figs. 4.2 and 4.3, suggest one advantage and one disadvantage of inhaling insulin rather than injecting it.

advantage ..................................................................................................................................................

disadvantage ........................................................................................................................................... [2]

Rice, Oryza sativa, is a staple food in many parts of the world. Rice is often grown in fields that are flooded with water for part of the growing season.

(a) The roots of young rice plants are highly tolerant of ethanol. Explain how this helps them to survive when the fields are flooded.
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(b) Rice grains have a similar structure to those of maize. The endosperm makes up most of the rice grain. The endosperm is surrounded by an aleurone layer, which contains hydrolytic enzymes. Outside the aleurone layer is the fused pericarp and testa, containing large amounts of cellulose.

(i) Describe the function of the endosperm.
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Brown rice includes the pericarp and testa, whereas in white rice these have been removed during milling, along with most of the aleurone layer.

Table 5.1 shows the nutrient content of samples of white and brown rice.

Table 5.1

[Table_1]

(ii) With reference to the structure of rice grains, suggest why brown rice contains more protein than white rice.
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(iii) Explain why brown rice contains less carbohydrate per gram than white rice.
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(iv) Explain why the grains of cereals such as rice are staple foods in many parts of the world.
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In sickle cell anaemia the recessive allele $Hb^S$ replaces the normal allele $Hb^A$.

• The frequency of $Hb^S$ is much higher in West Africa than in most parts of the world.
• The frequency of $Hb^S$ corresponds with the distribution of malaria.

(a) Explain what is meant by the term allele.
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(b) State whether the likely life expectancy is high or low in West Africa for individuals with the following genotypes. In each case give a reason for your answer.

$Hb^AHb^A$ ..............................................................................................................................
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$Hb^AHb^S$ ..............................................................................................................................
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$Hb^SHb^S$ ...............................................................................................................................
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(c) Explain why populations of West African descent living in the USA have a decreased frequency of the $Hb^S$ allele compared to West African populations.
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(a) Explain why the side shoots increase in length when the terminal buds are removed.
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(b) Calculate the percentage difference, at 13 days, in the mean length of side shoots of plants treated with paste alone compared with the plants treated with paste and auxin.
Give your answer to the nearest whole number.
Show your working.
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(c) Using data from Fig. 7.1, describe and explain the effect of auxin on the growth of side shoots.
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(a) In flowering plants, the light-dependent reactions are carried out by photosynthetic pigments which fall into two categories: primary pigments and accessory pigments.
Outline the role played by accessory pigments in the light-dependent reactions.
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(b) Photosynthetic pigments are arranged in photosystems. There are two photosystems, PS I and PS II. PS I takes part in cyclic photophosphorylation but PS II does not.
Outline the differences between cyclic and non-cyclic photophosphorylation.
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(c) The rate of photosynthesis is affected by several environmental factors. Fig. 8.1 shows the effect of temperature on the rate of photosynthesis.



(i) Explain why the rate of photosynthesis levels out at 30°C.
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(ii) On Fig. 8.1 continue the curve to indicate what would happen to the rate of photosynthesis if the temperature was increased to 70°C. [1]
(iii) Explain why you have continued the curve in this way.
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(d) A palisade mesophyll cell is adapted to carry out photosynthesis. The table below lists some of the adaptations of a palisade mesophyll cell.
Complete the table to show how these adaptations help the cell to carry out photosynthesis.

\begin{tabular}{|c|c|}\hline adaptation & how the adaptation helps photosynthesis \\ \hline thin cell wall & ......................................................................... \\ & ......................................................................... \\ \hline cylindrical shape & ......................................................................... \\ & ......................................................................... \\ \hline large vacuole & ......................................................................... \\ & ......................................................................... \\ \hline chloroplasts can be moved within the cell & ......................................................................... \\ & ......................................................................... \\ \hline \end{tabular} [4]

(a) Outline the behaviour of chromosomes during meiosis. [9]
(b) Describe the ways by which gene mutations can occur. [6]

(a) Outline the need for energy in living organisms using named examples. [9]
(b) Explain the different energy values of carbohydrate, lipid and protein as respiratory substrates. [6]
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