AQA A LEVEL BIOLOGY 7402/2 PAPER 2 QUESTION PAPER & MARK SCHEME [[VERIFIED]], Exams of Biology

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AQA A LEVEL

BIOLOGY 7402/

PAPER 2 QUESTION

PAPER AND MARK

SCHEME

{ MERGED} JUNE

2023 COMPLETE

AND UPDATED

Centre

number Candidate

number Surname

Forename(s)

Candidate

signature

I declare this is my own

work.

A-

level

For Examiner’s Use

3 4 5 6 7 8 9

10

TOTAL

Please write clearly in block capitals.

BIOLOGY

Paper 2

Friday 16 June 2023 Morning Time allowed: 2

hours

Materials

For this paper you must have:

• a ruler with millimetre measurements
• a scientific calculator.

Instructions

• Use black ink or black ball-point pen.
• Fill in the boxes at the top of this page.
• Answer all questions.
• You must answer the questions in the spaces provided.

Do not write outside the box around each page or on

blank pages.

• If you need extra space for your answer(s), use the lined pages at

the end of this book. Write the question number against your

answer(s).

• Show all your working.
• Do all rough work in this book. Cross through any work

you do not want to be marked.

Information

• The marks for the questions are shown in brackets.
• The maximum mark for this paper is 91.

Questio n

Mark

1

2

Do not write

• (^) IB/M/

Answer all questions in the spaces

provided.

outside the box

1 A student used chromatography to separate the different photosynthetic

pigments in a chlorophyll solution. She had the following materials.

Chromatography

paper A ruler and

pencil Suitable

glassware

A solvent (solvent A )

2 cm of the chlorophyll solution

Describe how she could use these materials to separate the

photosynthetic pigments by chromatography.

[4 marks]

2 Using solvent A , the student separated five pigments. She then repeated

her method using a different solvent, B. Using solvent B , she

separated six pigments.

Explain the difference between these results.

[2 marks]

Do not write outside the

• (^) IB/M/

1 Glutamate is a neurotransmitter involved in the transmission of nerve

impulses from pain receptors to the brain. Ziconotide is a drug that can

reduce severe, constant pain.

Ziconotide blocks the calcium ion channels at some of the synapses

which use glutamate.

The transmission of glutamate at synapses is similar to that of

acetylcholine.

box

Explain how ziconotide reduces severe, constant pain.

[5 marks]

Ziconotide is a polypeptide and acts on synapses in the spinal cord.

Scientists investigated the effectiveness of ziconotide in reducing severe,

constant pain.

Ziconotide was injected into each patient’s cerebrospinal fluid that

bathes the brain and spinal cord. Patients recorded the intensity of their

pain using a statistically valid scale.

2 Suggest two reasons why the patients had ziconotide injected

into their cerebrospinal fluid rather than taking a pill

containing the drug.

[2 marks]

Do not write outside the

• (^) IB/M/

Question 2 continues on the next page

Turn over ►

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• (^) IB/M/

3 Ziconotide was injected at 3 ng

kg

–

ng = 1 × 10

–

g

–

h for 8 days into each patient. 1

box

Calculate the total mass in grams of ziconotide injected after 8 days

into a patient with a body mass of 82 kg

Show your working.

[2 marks]

Answer g

4 When the patients recorded the intensity of pain, suggest two reasons

why it was important to use a statistically valid scale.

[2 marks]

Do not write outside the

• (^) IB/M/

0 3F

igure 1 shows part of a phosphorus cycle, including the mass of

phosphorus in two stores.

box

Figure 1

One teragram (Tg) is 1 × 10

grams.

The supply of phosphorus to the soil is shown as a percentage of

the total phosphorus mass of each store.

1 Calculate in teragrams the difference in the supply of phosphorus to the

soil from the two stores shown in Figure 1.

Show your

working. [2 marks]

Answer Tg

Question 3 continues on the next page

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• (^) IB/M/

Water shortage can inhibit crop production. Scientists investigated the

effect of the mycorrhizal species Glomus intraradices on the growth of

tomato plants under conditions of water shortage and no water

shortage.

• The scientists planted tomato seeds into a large number of pots

containing sterilised soil.

• They added a culture of G. intraradices to 50% of the pots and 50%

were left untreated.

• After the seeds had developed into seedlings (young plants), the

seedlings from the untreated and treated pots were planted into four

separate large greenhouses (glasshouses).

• A very limited supply of water (water shortage) was provided to two of

the greenhouses. A sufficient supply of water ( no water shortage) was

provided to the other two greenhouses.

• After 60 days, the scientists determined the mean mass of tomatoes (kg m

–

)

from each greenhouse.

Greenhouse P – untreated seedlings with water

shortage Greenhouse Q – treated seedlings with

water shortage Greenhouse R – untreated seedlings

with no water shortage Greenhouse S – treated

seedlings with no water shortage

Treated seedlings are plants grown with G. intraradices.

Figure 2 shows the scientists’ results.

The error bars represent ± 2 standard deviations from the

mean, which includes over 95% of the data.

box

Figure 2

Do not write outside the

• (^) IB/M/

0 3. 2 Using all the information, evaluate the effectiveness of using mycorrhizae

to increase crop production under conditions of water shortage and

no water shortage.

[5 marks]

Turn over

►

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• (^) IB/M/

box

0

Do not write outside the

• (^) IB/M/

3 The tomato seeds were planted into sterilised

soil.

Suggest two reasons why the soil was

sterilised.

[2 marks]

box

4 The soil used in this investigation had the recommended concentration of fertiliser.

Suggest two reasons why the soil contained the recommended

concentration of fertiliser.

[2 marks]

Do not write outside the

• (^) IB/M/

Turn over for the next question

DO NOT WRITE ON THIS PAGE

ANSWER IN THE SPACES PROVIDED

box

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• 12 *

IB/M/

X X Ff X

0 4 I

n cats, males are XY and females are XX. A gene on the X chromosome

controls fur colour in cats. The allele G codes for ginger fur and the allele

B codes for black fur. These alleles are codominant. Heterozygous

females have ginger and black patches of fur and their phenotype is

described as tortoiseshell female.

The two alleles, F and f of a different gene, which is not sex-linked, interact

with the gene controlling fur colour. The allele F is dominant and stops the

formation of pigment in the fur, resulting in white fur. The allele f is

recessive and has no effect on fur colour.

box

1 Name the type of interaction between the two genes affecting fur colour.

[1 mark]

2 What phenotype would a cat with the following genotype have?

[1 mark]

G B

X X ff

3 Complete the genetic diagram to show all the possible genotypes and

the ratio of phenotypes expected in the offspring of this cross.

Genotypes of parents

G G

x

B

[3 marks]

Genotypes of offspring

Phenotypes of offspring

Ratio of offspring

phenotypes

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• 13 *

IB/M/

0 4. 4 In a population, 36% of cats had the F allele and had white fur.

Use the Hardy–Weinberg equation to calculate the frequency of the

f allele in this population.

Show your working.

box

[2 marks]

Answer

Turn over for the next question

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• 14 *

IB/M/

0 5. 1 Figure 3 shows the wavelengths of light absorbed by three

types of photoreceptor found in the human retina.

Figure 3

Use Figure 3 and your knowledge of colour vision to explain how

an orange colour is seen at 600 nm

[3 marks]

box

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• 15 *

IB/M/

0 5. 2 Which of the following statements is associated with high

sensitivity to light in the retina?

✓ Tick ( ) one box.

[1 mark]

box

A single photoreceptor connecting to one neurone and spatial summation

A single photoreceptor connecting to one neurone and temporal summation

Several photoreceptors connecting to one neurone and spatial summation

Several photoreceptors connecting to one neurone and temporal

summation

Question 5 continues on the next page

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• 16 *

IB/M/

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• 17 *

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0 5. 3 Variation in flower colour is considered one of the factors involved in the

evolution of the following two species of monkeyflower.

• Erythranthe lewisii (Great Purple Monkeyflower), which has pink flowers,

is mostly found at higher altitudes (1600 to 3000 metres) and attracts

bumblebees.

• Erythranthe cardinalis (Scarlet Monkeyflower), which has red flowers, is

mostly found at lower altitudes (up to 2000 metres) and attracts

hummingbirds.

Bumblebees and hummingbirds are important in the pollination

of flowers. Pollination involves the transfer of male gametes to

female gametes.

Explain the different processes that may have been involved in the

evolution of these two species of monkeyflower. Use the information

provided to justify your answer.

[5 marks]

box

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• 18 *

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• 19 *

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Turn over for the next question

DO NOT WRITE ON THIS PAGE

ANSWER IN THE SPACES PROVIDED

box

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• 20 *

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1 Describe and explain how three features of the cells in the proximal

convoluted tubule allow the rapid reabsorption of glucose into

the blood. (^) [3 marks]

box

2 Antidiuretic hormone (ADH) binds to V receptors found in cell-surface

membranes in two parts of a nephron.

Name the two parts of a nephron where V receptors are found.

[1 mark]

3 V receptors only bind with

ADH. Suggest and

explain why.

[2 marks]

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• 21 *

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0 6. 4 A decrease in blood pressure stimulates the release of ADH.

Give the location of the receptors that detect a decrease in

blood pressure and explain how the release of ADH will affect

blood pressure. [3 marks]

box

Location

Explanatio

n

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• 22 *

IB/M/

1 In the following passage, the numbered spaces can be filled with

biological terms. An ecosystem supports a certain size of population

of a species, called

Write the correct biological term beside each number below that matches

the space in the passage.

box

[2 marks]

2 Suggest two reasons for conserving rainforests.

[2 marks]

3 Give three reasons for the low efficiency of energy transfer from

secondary consumers to tertiary consumers in an ecosystem.

[3 marks]

the (1) capacity. There are often numerous habitats within an

ecosystem.

Within a habitat, a species

occupies a

(2) governed by an adaption to

both (3) and biotic conditions. Populations of different species

Do not write outside the

• 23 *

IB/M/

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ANSWER IN THE SPACES PROVIDED

box

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• 24 *

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1 The KRAS gene codes for a protein called K-Ras. The protein relays signals

from outside a cell to a cell’s nucleus, stimulating cell division. An

alteration in the KRAS gene produces an oncogene which can cause a

tumour to develop.

Suggest and explain how an alteration in the KRAS gene can cause a

tumour to develop.

box

[3 marks]

2 Alterations in the KRAS gene can cause colorectal cancer (CRC). Scientists

investigated the survival time of the following three groups of CRC

patients who had type II diabetes.

Group A – received no drug to treat type II diabetes

Group B – received the drug metformin to treat type II diabetes

Group C – received a combination of drugs (including

metformin) to treat type II diabetes

The scientists used a statistical test to compare the survival time of

these patients with CRC patients with no history of type II diabetes.