AQA MERGED QUESTION PAPER AND MARK SCHEME BIOLOGY PAPER 2-7402/2 FOR JUNE 2024, Exams of Biology

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7402/

For Examiner’s Use

Question Mark 1 2 3 4 5 6 7 8 9

10

TOTAL

Friday 14 June 2024 Morning Time allowed: 2 hours

A-level

BIOLOGY

Paper 2

Do not write outside the Answer all questions in the spaces provided.^ box

(^0 1) Figure 1 shows a drawing of a neuromuscular junction.

Figure 1

(^0 1). 1 Name the parts labelled A to D. [2 marks]

A

B

C

D

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(^0 1). 2 Following the release of acetylcholine into a neuromuscular junction, a muscle contraction occurs.

Describe the sequence of events, following the release of acetylcholine, that leads to stimulation of this contraction.

Do not include in your answer the events following the release of calcium ions in the myofibril. [4 marks]

0 1. 3 Inhibitory synapses cause hyperpolarisation in postsynaptic neurones.

Explain how this inhibits synaptic transmission. [2 marks]

Do not write outside the (^0 2). 1 Figure 2 shows part of a relaxed myofibril.^ box

Figure 2

The myofibril represented in Figure 2 has 34 sarcomeres. The length of every sarcomere is 2 μm After contraction of this myofibril, the length of each sarcomere changed by 20%.

Use the information provided to calculate the length of the myofibril after contraction.

Give your answer in mm and in standard form.

Show your working. [2 marks]

Answer mm

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Do not write outside the (^0 2). 2 Which statement correctly describes the changes in length in a sarcomere when a^ box myofibril contracts?

Tick () one box. [1 mark]

H-zone decreases, I-band increases, A-band decreases

H-zone increases, I-band decreases, A-band decreases

H-zone decreases, I-band decreases, A-band no change

H-zone increases, I-band increases, A-band no change

0 2. 3 Fast muscle fibres have a higher concentration of glycogen than slow muscle fibres.

Explain how the difference in glycogen concentration is related to the different properties of these muscle fibres. [4 marks]

Do not write outside the (^0 3). 1 A biologist investigated photosynthesis. They:^ box

• measured the percentage of light absorbed by a plant when it was exposed to different wavelengths
• measured the rate of photosynthesis at each wavelength of light.

Figure 3 shows the results they obtained.

Figure 3

Using Figure 3 , what can you conclude about the relationship between: [2 marks]

the percentage of light absorbed and the rate of photosynthesis

the colour of light and the rate of photosynthesis

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Do not write outside the (^0 3). 2 Give three environmental factors that should be controlled when measuring the rate^ box of photosynthesis in this investigation.

Do not include features of the plant in your answer. [2 marks]

1

0 3. 3 Describe how the products of the light-dependent reaction are used in the light-independent reaction to produce triose phosphate.

Do not include the role of ribulose bisphosphate (RuBP) in your answer. [3 marks]

Do not write outside the (^0 4). 1 In fruit flies, a gene for body colour has a dominant allele for grey body, G , and a^ box recessive allele for black body, g.

Explain how you would determine if the genotype of a grey fly is homozygous or heterozygous for body colour. [2 marks]

0 4. (^2) In fruit flies, males are XY and females are XX.

A cross between a grey-bodied male fly and a black-bodied female fly produced some black-bodied females. Explain how this shows that the gene for body colour is not sex-linked. [1 mark]

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Do not write outside the (^0 4). 3 A population of fruit flies contained 19% grey-bodied flies.^ box

Use the Hardy–Weinberg equation to calculate the percentage of flies heterozygous for gene G.

Show your working. [2 marks]

Answer %

(^0 4). 4 In fruit flies, a gene for wing shape has a dominant allele for curly wings, R , and a recessive allele for normal wings, (^) r. The alleles for this gene are on a different pair of chromosomes from the gene for body colour.

Fruit flies that are homozygous dominant for curly wings do not survive beyond the embryo stage.

A curly-winged fly, homozygous for grey body colour was crossed with a curly-winged, black-bodied fly.

Complete the genetic diagram to show all the possible genotypes and the ratio of phenotypes expected to develop into adults from this cross. [3 marks]

Phenotypes of parents Curly-winged, grey-bodied, × Curly-winged, black-bodied

Genotypes of parents ×

Genotypes of offspring

Phenotypes of offspring

Ratio of offspring^8

Do not write outside the (^0 5). 1 A weed is a plant growing where it is not wanted. Fat hen is a weed which grows in^ box some crop fields.

Describe how you could estimate the number of fat hen plants in a field. [5 marks]

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Do not write outside the (^0 5). 2 In potato plant fields, fat hen plants can grow up to a height of 2 m and absorb large^ box quantities of nutrients from the soil.

Fat hen has a negative effect on the growth of potato plants.

Use the information provided to explain why.

In your answer, name the type of competition occurring between fat hen plants and potato plants. [3 marks]

Question 5 continues on the next page

Do not write outside the (^0 5). 3 Table 1 gives some features of fat hen seeds.^ box

Table 1

Feature of seed

Mean mass / mg 0.

Maximum number produced per fat hen plant during a growing season 20 000

Percentage viable (able to develop) after a growing season 79

During a growing season, it was estimated that a total number of 550 fat hen plants grew on the fields of a farm.

Calculate the maximum mass, in kg, of viable fat hen seeds on this farm after a growing season.

Show your working.

Assume that all the seeds produced during the growing season remain on the farm. [2 marks]

Answer kg^10

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ANSWER IN THE SPACES PROVIDED

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Do not write outside the (^0 6). 1 Describe the myogenic stimulation of the heart and how the regular contraction of the^ box atria and ventricles is coordinated.

Do not include the autonomic nervous system in your answer. [5 marks]

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Do not write outside the (^0 6). 2 Atrial fibrillation (AF) is a condition that causes an irregular heart rate. Scientists used^ box a statistical test to investigate the association between different factors and the risk of developing AF.

Table 2 shows some of the scientists’ results, including the probability (P) values obtained using the statistical test.

Table 2

Factor Probability (P) value for associationbetween factor and risk of AF

Age 0.

High blood pressure 0.

High LDL (Low-density lipoprotein) concentration

0.

Hyperthyroidism 0.

What can you conclude from Table 2? [3 marks]

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Do not write outside the (^0 7). 1 Bam H1 and Hin dIII are both restriction endonucleases.^ box

Figure 4 shows the positions where these enzymes cut a linear molecule of DNA.

Figure 4

In two experiments, multiple copies of the DNA molecule shown in Figure 4 were all completely cut into fragments using these restriction enzymes. The DNA fragments produced were then separated by electrophoresis.

Experiment 1 – DNA cut into fragments using Bam H1.

Experiment 2 – DNA cut into fragments using Bam H1 and Hin dIII.

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Do not write outside the Complete Figure 5 to show the relative positions of the bands following^ box electrophoresis in experiments 1 and 2. [2 marks]

Figure 5

0 7. 2 Suggest how you could determine the size of the different DNA fragments produced in these experiments. [2 marks]

Do not write outside the (^0 7). 3 How many DNA fragments would be produced in experiment 2 if the original DNA^ box molecule was a plasmid? [1 mark]

(^0 7). 4 Describe how restriction endonuclease and DNA ligase are used to insert a gene into a plasmid. [2 marks]

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Do not write outside the (^0 8) Plant cells are surrounded by a rigid cell wall. Cell wall plasticity refers to the ability of^ box a cell wall to stretch permanently. IAA is a growth factor which can activate enzymes that loosen the cell wall.

Scientists investigated the effect of IAA concentration on cell wall plasticity and the growth of stem segments.

Figure 6 shows some of the scientists’ results.

Figure 6

(^0 8). 1 Use the information provided to explain the relationship between IAA concentration, cell wall plasticity and mean growth of the stem segments. [2 marks]

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Do not write outside the (^0 8). 2 Use Figure 6 to calculate the percentage increase in mean growth of the stem^ box segments when the IAA concentration was increased from 10 –8^ mol dm–3 to 10 –5^ mol dm–3

Give your answer to 2 significant figures.

Show your working. [2 marks]

Answer %

Question 8 continues on the next page

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Do not write outside the Gibberellic acid (GA) is another plant growth factor. A student was asked to design^ box and carry out an investigation into the effect of different concentrations of GA on the growth of stem segments.

The student was provided with:

• 10 –1, 10 –2, 10 –3, 10 –4^ and 10 –5^ mol dm–3^ concentrations of GA solution
• distilled water
• 6 Petri dishes and access to glassware
• 60 stem segments of different lengths.

0 8. 3 A technician produced the different concentrations of GA solution from a stock 10 –1^ mol dm–3^ concentration of GA.

Describe how the technician produced the 10 –3^ mol dm–3^ solution. [1 mark]

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Do not write outside the (^0 8). 4 Describe a suitable procedure the student could follow to investigate the effect of^ box different concentrations of GA on the growth of stem segments.

In your answer, you should include the variables that should be controlled in this investigation. [5 marks]

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Do not write outside the (^0 9) A person with diabetes is in diabetes remission if their blood glucose concentration is^ box below the diabetes threshold concentration for at least 3 months. This diabetes remission is achieved without taking medication.

Scientists investigated whether a weight-loss programme would result in type II diabetes remission.

The scientists:

• used a computer-generated list to select 380 volunteers from a large number of health centres
• selected volunteers aged 25 to 60 years, each with less than 5 years duration of type II diabetes
• divided the volunteers in the ratio 1 : 1 between experimental group P and control group Q
• placed group P on a weight-loss programme for the 2-year duration of this investigation
• recorded loss of mass and percentage of volunteers in each group in type II diabetes remission after 2 years.

(^0 9). 1 Give two reasons why a weight-loss programme could be used to treat type II diabetes but not type I diabetes. [2 marks]

1

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