AQA A Level Biology Paper 2 June 2024 question paper 7402/2

Figure 1 shows a drawing of a neuromuscular junction.

Name the parts labelled A to D.

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.

Inhibitory synapses cause hyperpolarisation in postsynaptic neurones.

Explain how this inhibits synaptic transmission.

Figure 2 shows part of a relaxed myofibril.

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.

Which statement correctly describes the changes in length in a sarcomere when a myofibril contracts?

Tick (✓) one box.

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.

A biologist investigated photosynthesis. They:

• 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.

Using Figure 3, what can you conclude about the relationship between:

the colour of light and the rate of photosynthesis

Give three environmental factors that should be controlled when measuring the rate of photosynthesis in this investigation.

Do not include features of the plant in your answer.

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.

In fruit flies, a gene for body colour has a dominant allele for grey body, G, and a 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.

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.

A population of fruit flies contained 19% grey-bodied flies.

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

Show your working.

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.

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

Genotypes of offspring

Phenotypes of offspring

Ratio of offspring

A weed is a plant growing where it is not wanted. Fat hen is a weed which grows in some crop fields.

Describe how you could estimate the number of fat hen plants in a field.

In potato plant fields, fat hen plants can grow up to a height of 2 m and absorb large 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.

Table 1 gives some features of fat hen seeds.

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.

Describe the myogenic stimulation of the heart and how the regular contraction of the atria and ventricles is coordinated.

Do not include the autonomic nervous system in your answer.

Atrial fibrillation (AF) is a condition that causes an irregular heart rate. Scientists used 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.

What can you conclude from Table 2 ?

Bam H1 and Hin dIII are both restriction endonucleases.

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

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.

Complete Figure 5 to show the relative positions of the bands following

electrophoresis in experiments 1 and 2.

Suggest how you could determine the size of the different DNA fragments produced in these experiments.

How many DNA fragments would be produced in experiment 2 if the original DNA molecule was a plasmid?

Describe how restriction endonuclease and DNA ligase are used to insert a gene into a plasmid.

Plant cells are surrounded by a rigid cell wall. Cell wall plasticity refers to the ability of 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.

Use the information provided to explain the relationship between IAA concentration, cell wall plasticity and mean growth of the stem segments.

Use Figure 6 to calculate the percentage increase in mean growth of the stem segments when the IAA concentration was increased from 10^–8 mol dm^–3

Give your answer to 2 significant figures.

Show your working.

Gibberellic acid (GA) is another plant growth factor. A student was asked to design

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.

A technician produced the different concentrations of GA solution from a stock

Describe how the technician produced the 10^–3 mol dm^–3 solution.

Describe a suitable procedure the student could follow to investigate the effect of 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.

A person with diabetes is in diabetes remission if their blood glucose concentration is 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.

Give two reasons why a weight-loss programme could be used to treat type II diabetes but not type I diabetes.

The design of this investigation helps to support the validity of any conclusions obtained.

Suggest and explain three features of this investigation that justify this statement.

Table 3 shows some of the scientists’ results.

Use the information provided to calculate the difference in number of volunteers between the two groups who achieved diabetes remission.

Show your working.

Use all the information to evaluate whether a weight-loss programme is an effective treatment for type II diabetes.

Read the following passage.

The wall gecko is a medium-sized lizard. In an isolated habitat of southern Italy, the wall gecko shows phenotypic diversity. Scientists investigated whether disruptive selection was leading to sympatric speciation in the wall gecko.

Pale geckos live only on walls and are nocturnal (active at night). Dark geckos 5 live mainly on the dark trunks of olive trees and are diurnal (active during the day). These diurnal geckos can change skin colour when occupying different surfaces during the day.

Comparison of mitochondrial genes indicated that the diurnal geckos formed a distinct genetic group. This comparison also confirmed that all the geckos in 10 the habitat were of the same species.

The scientists used the mark-release-recapture method to estimate the size of the population of geckos in the habitat.

Use the information in the passage and your own knowledge to answer the following questions.

The wall gecko shows phenotypic diversity (lines 1–2).

Suggest two factors that have resulted in this phenotypic diversity.

The ability of diurnal geckos to change skin colour (lines 7–8) is advantageous.

Explain why.

The scientists concluded that it was probable that disruptive selection was leading to sympatric speciation in the wall gecko.

Use the information in the passage to evaluate this conclusion.

Explain how comparison of mitochondrial genes could indicate that the nocturnal geckos formed a distinct genetic group (lines 9–10).

In your answer, explain how new techniques enable the comparison of genes to be completed rapidly.

Describe and explain two precautions required to ensure that the estimate of the size of the population of geckos was valid (lines 12–13).

Do not include sample size as one of the required precautions.

In your answer, include the formula to estimate the size of the population using the mark-release-recapture method.