Biology B · Edexcel 9BI0 · Paper 2: Advanced Physiology, Evolution and Ecology · June 2025
The photograph shows part of a liver cell, as seen using an electron microscope.
(Source: © Keith R. Porter/SCIENCE PHOTO LIBRARY)
Describe the roles of the labelled organelles in a liver cell.
(3)
Hepatitis B is a DNA virus that infects liver cells. The DNA of the virus replicates inside liver cells.
Describe the process of DNA replication.
(3)
(2)
The diagram shows the process of oogenesis.
Which is the name of the cell labelled X?
(1)
Meiosis is involved in oogenesis.
Describe the events of prophase I during oogenesis.
(3)
Compare and contrast the process of oogenesis with spermatogenesis.
(3)
During in vitro fertilisation (IVF), oocytes are fertilised with sperm cells in a culture medium.
If more than one sperm cell fertilises an oocyte, the embryos do not develop.
The graph shows the effect on the production of embryos that develop when different numbers of sperm cells are added to oocytes during IVF.
Number of sperm cells per oocyte
1000
Calculate the number of sperm cells that need to be added to four oocytes so that 60% of embryos develop.
(1)
Analyse the data to explain the effects of increasing the number of sperm cells per oocyte on the percentage of embryos that develop.
(2)
Stress can change the heart rate of a person.
The diagram shows an ECG trace for a student at rest.
Which of the letters on this ECG trace represents the time when ventricular systole occurs?
(1)
Describe how myogenic stimulation maintains the heart rate of the student when at rest.
(3)
Scientists investigated the effect of an anti‑anxiety drug on the change in heart rate of a student after a sudden fright.
In this investigation:
• The resting heart rate of the student was measured.
• The student was given a sudden, unexpected fright and their heart rate was measured again.
• This was repeated four more times.
• The investigation was then repeated after the student had taken the anti‑anxiety drug.
The table shows the results of this investigation.
| Heart rate / beats per minute | ||||
| Fright number | without anti‑anxiety drug | with anti‑anxiety drug | ||
| resting | after fright | resting | after fright | |
| 1 | 64 | 135 | 46 | 70 |
| 2 | 56 | 125 | 54 | 65 |
| 3 | 55 | 125 | 48 | 70 |
| 4 | 75 | 110 | 56 | 105 |
| 5 | 72 | 105 | 48 | 65 |
The mean volume of blood pumped around the body in one minute after a fright without the anti‑anxiety drug is 18 dm3.
The stroke volume of the student’s heart was 150 cm3.
Calculate the mean volume of blood pumped around the body in one minute after a fright, when taking the anti‑anxiety drug.
Give your answer in dm3 and to the nearest whole number.
(2)
The anti‑anxiety drug has a similar shape to noradrenaline.
Analyse the data to comment on the results of this investigation.
(4)
Which type of bond is used when forming both the secondary structure and tertiary structure of proteins?
(1)
Which type of mutation has occurred to produce the allele for sickle cell anaemia?
(1)
(2)
The graph shows the range of oxygen dissociation curves for haemoglobin taken from people who do not have sickle cell anaemia (unaffected) and from people with sickle cell anaemia (affected).
The shaded areas represent the ranges for each blood sample.
Compare and contrast the properties of haemoglobin from these two groups of people.
(2)
There is only one known allele that causes sickle cell anaemia.
State how the graph suggests that other genes affect the phenotype of people affected by sickle cell anaemia.
(1)
Explain why the oxygen dissociation curve for people with sickle cell anaemia means that they have difficulty exercising.
(3)
Auxin is a plant growth substance.
Which of the following are functions of auxin?
1. inhibiting lateral shoot growth
2. stimulating the elongation of cells in plant stems
3. stimulating flowering
(1)
In an investigation, wheat seedlings were exposed to different concentrations of auxin.
The mean lengths of the roots and the mean dry biomass of the seedlings were calculated.
The graphs show the results of this investigation.
Auxin concentration / μmol dm–3
Auxin concentration / μmol dm–3
Calculate the percentage increase in mean root length when given an auxin concentration of 10–4 μmol dm–3 compared with no auxin.
Give your answer to the nearest whole number.
(1)
Analyse the data to discuss the effects of auxin on the growth of wheat seedlings.
(4)
The photograph shows a brown rat, Rattus norvegicus.
(Source: © DK IMAGES/SCIENCE PHOTO LIBRARY)
The classification hierarchy for the brown rat is:
• Domain: Eukarya
• Kingdom: Animalia
• Phylum: Chordata
• Mammalia
• Rodentia
• Muridae
• Genus: Rattus
• Species: norvegicus.
Which family, order and class does the brown rat belong to?
(1)
State one method that scientists use to determine the evolutionary relationships of the brown rat compared with other species.
(1)
Calculate the expected number of rats that would be resistant to warfarin but do not require large amounts of vitamin K to survive, before warfarin was used.
Use the Hardy‑Weinberg equation
(3)
Explain why, after two years, there is a change in the number of rats that are resistant to warfarin.
(2)
Warfarin is highly toxic to rats that have no resistance.
Explain why, after five years, there are still many rats that are not resistant to warfarin.
(2)
Inulin is a polysaccharide made of fructose that is used as a storage molecule by some plant species.
The diagram shows part of a molecule of inulin.
The inulin molecule in the diagram contains fructose.
Which of these carbohydrates also contain fructose?
(1)
Which is the name of the chemical bond that joins the monosaccharides in inulin?
(1)
Fructose has the same molecular formula as glucose.
Which is the molecular formula of a molecule of inulin consisting of four fructose sugars?
(1)
The number of fructose molecules in inulin can vary from 10 to 70.
Inulin with high numbers of fructose molecules is less soluble in water.
The diagram shows three plant cells with different water potentials.
Draw arrows on the diagram to show the direction of water movement between the cells.
(1)
Explain why some plant species make inulin with fewer fructose molecules in dry weather and inulin with more fructose molecules in wet weather.
(2)
Inulin is used to measure the rate of filtration by the kidneys.
A saline solution containing inulin is injected into the vein of a patient.
The concentration of inulin in the blood plasma is then measured over time.
The rate of filtration is a measure of the maximum rate that inulin is removed from the blood by the kidneys.
The graph shows the concentration of inulin in the blood plasma after an injection of 5 g of inulin.
Calculate the maximum rate that the inulin is removed from the blood.
Give your answer to two decimal places with appropriate units.
(2)
Explain how inulin passes from the blood plasma into the proximal convoluted tubule of a nephron.
(2)
Explain why all the inulin is released into the urine.
(2)
The photograph shows a grouse on a heather moor. Heather moors are areas of countryside that are dominated by heather plants.
(Source: © Ben Hall/2020VISION/Nature Picture Library/SCIENCE PHOTO LIBRARY)
Heather moors are habitats for a variety of plants and animals. They are also used for sheep farming and as areas to raise grouse.
The net primary productivity (NPP) of a heather moor decreases with the age of the heather plants.
Which of the following is the correct formula to calculate NPP?
(1)
As heather plants age, the ratio of leaf area to area of woody stem changes.
A student investigated the relationship between the age of heather plants and the ratio of leaf area: woody stem area.
The student carried out a Spearman’s rank correlation test using the data in the table.
| Age of heather plant / years | Rank of age of heather plant | Ratio of leaf area : woody stem area | Rank of leaf area : woody stem area | d | d2 |
| 16 | 4 | 0.7 | 4.5 | –0.5 | 0.25 |
| 15 | 5 | 0.4 | 8 | –3 | 9 |
| 12 | 6 | 0.6 | 6 | 0 | 0 |
| 4 | 9 | 2.0 | 1 | 8 | 64 |
| 7 | 8 | 1.1 | 5.5 | 30.25 | |
| 22 | 1 | 0.2 | 10 | –9 | 81 |
| 20 | 2 | 0.3 | 9 | –7 | 49 |
| 3 | 10 | 1.1 | |||
| 17 | 3 | 0.5 | 7 | –4 | 16 |
| 11 | 7 | 0.7 | 4.5 | 2.5 | 6.25 |
Calculate the missing values to complete the table. Write your answers in the table.
(2)
Calculate the Spearman’s rank correlation coefficient for the data in the table. Use the formula
(3)
The table gives some critical values for the Spearman’s rank correlation coefficient.
| n | Level of significance | |
| P = 0.05 | P = 0.01 | |
| 5 | 1.000 | – |
| 6 | 0.886 | 1.000 |
| 7 | 0.786 | 0.929 |
| 8 | 0.738 | 0.881 |
| 9 | 0.700 | 0.833 |
| 10 | 0.648 | 0.794 |
| 11 | 0.618 | 0.755 |
Comment on the relationship between the age of the heather and the ratio of leaf area to woody stem area.
Use your calculated value of Spearman’s rank correlation coefficient and the table.
(3)
*(c) Farmers manage heather moors by burning the heather every 10 years. This removes older heather and allows younger plants to grow.
Managing heather moors by burning is controversial.
It has been suggested that instead of burning the heather, the moors should be left to return to nature as part of a rewilding strategy.
Rewilding strategies aim to return areas of farmland to the original ecosystems that existed before the heather moors.
Several factors have to be considered before a decision on rewilding is made.
• The heather moors are areas of peat containing dead organic waste that decomposes very slowly.
• Heather moors are an area of income for farmers.
• Over time, heather becomes very dominant and lies flat over the ground, blocking light.
• A variety of small species of plants live around areas of older heather.
• Heather seeds need to be heated to germinate efficiently.
• Some endangered species consume grouse.
• Grouse are raised by humans for profit.
• Heather moors have been managed for many years and many species that lived in the area are now extinct.
Analyse all the information in the question to discuss the effects of rewilding the moors compared with management by burning.
(6)
The diagram shows a section through the central area of a human retina.
Draw an arrow on the left of the diagram to show the direction that light travels through the retina.
(1)
Describe how light absorbed by rhodopsin in a rod cell leads to a change in release of neurotransmitter from the rod cell.
(3)
*(b) A student investigated the retinal structures of different mammals.
The student collected information about:
• the structure of the retina of the cat (a predator that hunts at night)
• the distribution of rods and cones in the retina of humans and cats
• the total number of rods and cones in the retinas of species active in the day and species active at night.
The diagram shows part of the retina of a cat.
Table 1 and Table 2 show some of the data collected by the student.
Discuss how the retinas of animals are adapted to their activity at different times of the day.
(6)
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