Edexcel GCSE Biology Paper 2, Higher Tier (1BI0/2H)Paper 2 — every question, answered
We read the real Higher Tier papers Edexcel has published for Biology Paper 2 in June 2019, June 2022 and June 2023, plus the mark schemes examiners actually used to grade them. Below is what real sub-questions on each topic have asked, what a full-mark answer looks like against that year's mark scheme, and what tripped candidates up. All three sittings are verified directly from Pearson's own published PDFs.
Questions © Pearson Education Ltd, quoted for analysis. Diagrams and photographs described in our own words, not reproduced. Mark scheme content translated into plain English, not copied. PrepWise is independent and not endorsed by Pearson or Edexcel.
The paper is a template
Same 16 question types, every sitting“Explain what causes high blood glucose in type 2 diabetes and how it is controlled”
All three sittings test type 2 diabetes, mixing a graph or blood-test data question with a straight explain question on the mechanism or its control.
1×asked“Excessive weight gain and obesity increase the likelihood of developing type 2 diabetes. Explain the effect of type 2 diabetes on the body.”
“Excessive weight gain and obesity increase the likelihood of developing type 2 diabetes. Explain the effect of type 2 diabetes on the body.”
What it’s really asking
It wants the mechanism: blood glucose levels are not regulated because body cells become resistant to insulin, so the liver does not convert enough glucose into glycogen, leaving blood glucose high.
The full worked answer — June 2022
In type 2 diabetes, blood glucose levels are not properly regulated and stay high, because body cells become resistant to insulin, meaning they no longer respond normally to it.
Because the liver cells do not respond properly to insulin, the liver does not convert as much glucose into glycogen for storage, so glucose remains in the blood at a higher concentration than normal.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise glucose regulationWhat the mark scheme rewarded
- Blood glucose levels are not regulated/are high
- Because cells are resistant to insulin/unresponsive to insulin
- So the liver does not convert glucose to glycogen
- Type 2 diabetes usually develops in adulthood and is strongly linked to obesity and inactivity, unlike type 1 diabetes which is an autoimmune condition destroying insulin-producing cells
- Persistently high blood glucose (hyperglycaemia) can damage blood vessels and nerves over time if type 2 diabetes is not controlled
Traps examiners saw
- Describing type 1 diabetes (the pancreas fails to produce insulin) instead of type 2 (the cells fail to respond to insulin), these are different mechanisms and the mark scheme rewards the correct one for the question asked
Full-mark self-check 0 of 3
1×asked“Explain how type 2 diabetes can be controlled.”
“Explain how type 2 diabetes can be controlled.”
What it’s really asking
It wants named, genuinely distinct lifestyle and medical control measures for type 2 diabetes, each linked to the goal of reducing or controlling blood glucose.
The full worked answer — June 2023
Type 2 diabetes can be controlled through regular exercise, which helps the body's cells respond better to insulin and use up glucose from the blood.
A person can also control their diet and lose weight, for example by reducing the amount of sugar and carbohydrate they eat, since excess weight is strongly linked to insulin resistance.
In addition, blood glucose levels can be monitored regularly, and medication such as metformin or insulin can be taken if diet and exercise alone are not enough to reduce blood glucose to a safe level.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise glucose regulationWhat the mark scheme rewarded
- Exercise
- Control diet/lose weight (accept avoid sugar/carbohydrate in diet)
- To reduce/control blood glucose
- Monitor/test blood glucose
- Take medication (metformin/insulin)
- Type 2 diabetes is often managed first through lifestyle changes before medication is introduced, unlike type 1 diabetes which always requires insulin injections
- Metformin is a common oral medication for type 2 diabetes that helps the body use insulin more effectively
Traps examiners saw
- Giving three versions of the same idea (for example, 'eat less sugar', 'eat healthily', 'reduce carbohydrates') instead of three genuinely distinct measures across lifestyle, monitoring, and medication
Full-mark self-check 0 of 3
The method for every Q2/Q6/Q2 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Linking insulin resistance specifically to cells not responding, not just 'not enough insulin'
- Naming the liver's role converting glucose to glycogen and vice versa
- Giving genuine lifestyle control measures (diet, exercise, weight loss) rather than vague 'eat healthily'
The steps
- State whether the question is about the CAUSE of high glucose (cell/insulin resistance) or the CONTROL of it (lifestyle measures)
- For the cause, always mention insulin resistance specifically, not just 'the pancreas doesn't work', since type 2 diabetes is a receptor problem not a production problem
- For control, give three genuinely different measures: exercise, diet/weight control, and monitoring or medication
Which organ monitors blood glucose concentration and secretes insulin and glucagon?
Type 2 diabetes questions test both the mechanism (insulin resistance) and the control measures (lifestyle and monitoring). Learn both halves.
Practise glucose regulation“Explain how sweating cools the body, controlled by the hypothalamus”
Both sittings we have test the hypothalamus as the temperature-control centre and the mechanism of sweat evaporation cooling the skin.
2×asked“Which part of the body controls the regulation of body temperature?”
“Which part of the body controls the regulation of body temperature?”
What it’s really asking
It wants the single correct brain structure, the hypothalamus, distinguished from the cerebellum, medulla oblongata and pituitary gland.
The full worked answer — June 2019
The hypothalamus.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise temperature regulationWhat the sources actually showed — June 2023
A labelled diagram of the insulation investigation apparatus: a beaker of hot water wrapped in wool or polyester, sealed with a lid, with a thermometer inserted through the lid, standing on an insulating mat.
The full worked answer — June 2023
The hypothalamus.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise temperature regulationWhat the mark scheme rewarded
- The single correct answer: hypothalamus
- The hypothalamus continuously monitors blood temperature and triggers responses such as sweating, shivering, and changes to blood vessel diameter to keep body temperature close to 37 degrees Celsius
- The pituitary gland releases hormones but does not itself detect or directly control temperature
Traps examiners saw
- Confusing the hypothalamus with the pituitary gland, since both are small structures near the base of the brain but have very different roles
Full-mark self-check 0 of 1
1×asked“Wearing an insulated jacket may cause a person to sweat. Explain how sweating helps to regulate temperature in humans.”
“Wearing an insulated jacket may cause a person to sweat. Explain how sweating helps to regulate temperature in humans.”
What it’s really asking
It wants the chain: sweat is released onto the skin, it evaporates, and evaporation removes heat/thermal energy from the body, cooling it down.
The full worked answer — June 2023
Sweat is released onto the surface of the skin from sweat glands, and this sweat then evaporates.
As the sweat evaporates, it takes thermal energy from the skin's surface with it, cooling the body down and helping to bring its temperature back towards normal.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise temperature regulationWhat the mark scheme rewarded
- Sweat/water is released onto the skin
- Which evaporates
- Transferring thermal energy/heat (away from the body)
- Evaporation requires energy, and this energy is taken from the body's surface, which is why evaporating sweat has a cooling effect
- In hot or humid conditions where sweat cannot evaporate as effectively, cooling by sweating becomes less efficient
Traps examiners saw
- Saying 'sweating cools the body down' without explaining the mechanism (evaporation transferring heat away), which is what actually earns the marks
Full-mark self-check 0 of 3
The method for every Q4/Q4 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Naming the hypothalamus specifically as the temperature-control centre, not a different brain region
- Linking sweat release to evaporation to heat loss, in that order, not just 'sweating cools you down'
The steps
- Distinguish the hypothalamus (temperature) from the cerebellum (balance), medulla oblongata (involuntary actions) and pituitary gland (hormone release), all common wrong options
- For sweating, state the three-step chain: release onto skin, evaporation, heat removed
- Use 'thermal energy' or 'heat' language rather than just 'the body gets colder'
What is the normal core body temperature in humans?
Temperature regulation questions always want the hypothalamus named correctly and the full sweat-evaporation-cooling chain explained.
Practise temperature regulation“Describe the route of urine formation, how urea is made, and how ADH controls water reabsorption”
Both sittings test the kidney system in depth, from urea production through to the full hormonal (ADH) control of the water content of the blood.
2×asked“Sweat contains urea. State where and how urea is produced in the human body.”
“Sweat contains urea. State where and how urea is produced in the human body.”
What it’s really asking
It wants the specific site (the liver) and the specific process (breakdown of excess amino acids, deamination) that produces urea.
The full worked answer — June 2019
Urea is produced in the liver, from the breakdown of excess amino acids that the body cannot store.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise water regulationThe full worked answer — June 2023
Urea is produced in the liver, by the breakdown of excess amino acids or protein, in a process called deamination.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise water regulationWhat the mark scheme rewarded
- Urea is produced in the liver
- From the breakdown of (excess) amino acids/protein (accept the term deamination)
- The body cannot store excess amino acids, so they are broken down in the liver, releasing ammonia which is then converted into the less toxic urea
- Urea is transported in the blood plasma to the kidneys, where it is filtered out and excreted in urine
Traps examiners saw
- Saying urea is produced 'in the kidney', the kidney filters urea out of the blood but does not produce it, production happens in the liver
Full-mark self-check 0 of 2
1×asked“Describe how the water content of the blood is controlled in the nephron.”
“Describe how the water content of the blood is controlled in the nephron.”
What it’s really asking
It wants the full negative-feedback loop in both directions: when blood water is too low, ADH release increases collecting duct permeability and more water is reabsorbed producing concentrated urine; when blood water is too high, ADH release decreases and more dilute urine is produced.
The full worked answer — June 2023
If the water content of the blood is too low, the hypothalamus detects this, and the pituitary gland responds by releasing more ADH (antidiuretic hormone) into the blood.
More ADH makes the walls of the collecting duct more permeable to water, so more water is reabsorbed back into the blood by osmosis. This means a smaller volume of more concentrated urine is produced, conserving water in the body.
If the water content of the blood is too high, the opposite happens: the hypothalamus detects this and less ADH is released from the pituitary gland, making the collecting duct less permeable to water.
As a result, less water is reabsorbed back into the blood, and a larger volume of more dilute urine is produced, removing the excess water from the body.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise water regulationWhat the mark scheme rewarded
- Water content too low: hypothalamus detects too little water in the blood; ADH released from the pituitary gland; collecting duct becomes more permeable; more water reabsorbed by osmosis; more concentrated, smaller-volume urine produced
- Water content too high: hypothalamus detects too much water in the blood; ADH lowered/not released; collecting duct is less permeable; less water reabsorbed; more dilute, larger-volume urine produced
- Level 3 (5 to 6 marks) requires a detailed description of BOTH directions, linked to ADH and the pituitary gland and the effect on collecting duct/nephron permeability
- ADH stands for antidiuretic hormone, and 'antidiuretic' means it acts against producing a large volume of urine, hence more ADH means less urine produced
- This is a classic negative feedback loop: a change in one direction triggers a response that pushes the system back towards the normal water balance
Traps examiners saw
- Only describing what happens when water content is too low, missing the too-high direction entirely, which caps the answer below Level 3 even if the low-water explanation is detailed and correct
- Naming the wrong gland as releasing ADH (it is the pituitary gland, not the hypothalamus itself, though the hypothalamus does the detecting)
Full-mark self-check 0 of 4
The method for every Q6/Q10 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Naming deamination and the liver specifically as where urea is produced from excess amino acids
- Building the full ADH negative-feedback loop, both directions: too little water AND too much water
- Linking ADH release from the pituitary gland to collecting duct permeability, not just 'ADH controls water'
The steps
- For urea, always name the liver as the site and amino acid breakdown (deamination) as the process, not the kidney
- For the full water-control question, cover BOTH directions of the loop, low water and high water, since Level 3 explicitly requires both
- Name the hormone ADH from the pituitary gland and its effect on collecting duct permeability specifically
Where does the filtration of blood take place in the kidney?
Water regulation questions want the FULL ADH loop in both directions, not just one scenario. Practise building both halves.
Practise water regulation“Explain how FSH and LH cause ovulation, and how hormone levels change with pregnancy or thyroid disease”
All three sittings test hormone interactions in the body: the menstrual cycle across two sittings, and thyroid hormone data interpretation in the third.
1×asked“Explain how two of the hormones shown cause ovulation.”
“Explain how two of the hormones shown cause ovulation.”
What it’s really asking
It wants the causal chain linking FSH to follicle maturation and oestrogen release, and then high oestrogen triggering the LH surge that causes ovulation.
What the sources actually showed — June 2023
Two linked graphs showing the changes in FSH, LH, oestrogen and progesterone levels across the days of a menstrual cycle, with ovulation marked at day 14.
The full worked answer — June 2023
FSH causes an egg (inside a follicle) to mature in the ovary, and FSH also stimulates the follicle to release oestrogen.
As the oestrogen level rises to a high peak just before day 14, this high level of oestrogen triggers a surge in LH.
This surge in LH is what directly causes ovulation, the release of the mature egg from the ovary.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise hormones and the menstrual cycleWhat the mark scheme rewarded
- FSH causes the egg/follicle to mature
- FSH stimulates oestrogen (release)
- High levels of oestrogen (trigger)
- LH/LH surge
- Causes the egg to be released
- The menstrual cycle is controlled by four hormones released from the pituitary gland and ovaries: FSH, LH, oestrogen and progesterone, each with a distinct role
- The LH surge is a sharp, short spike in LH concentration, distinct from the more gradual rise and fall of oestrogen across the cycle
Traps examiners saw
- Saying 'oestrogen causes LH' without specifying that it must be a HIGH level of oestrogen that triggers the surge, since a low oestrogen level does not trigger ovulation
Full-mark self-check 0 of 4
1×asked“Explain how the levels of each hormone in the woman shown would be different, if she was pregnant.”
“Explain how the levels of each hormone in the woman shown would be different, if she was pregnant.”
What it’s really asking
It wants the changes to all four hormones if pregnancy occurred: FSH and LH staying low because they are inhibited, and progesterone and oestrogen staying high to maintain the uterus lining.
What the sources actually showed — June 2023
Two linked graphs showing the changes in FSH, LH, oestrogen and progesterone levels across the days of a menstrual cycle, with ovulation marked at day 14.
The full worked answer — June 2023
If the woman was pregnant, FSH levels would remain low throughout, since no further egg or follicle would need to mature.
LH levels would also remain low, so that ovulation would not occur again during the pregnancy.
Progesterone levels would remain high, because progesterone inhibits FSH and LH, and high progesterone is needed to maintain the lining of the uterus throughout the pregnancy.
Oestrogen levels would also remain high, since high oestrogen helps to build and maintain the lining of the uterus that supports the developing pregnancy.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise hormones and the menstrual cycleWhat the mark scheme rewarded
- FSH levels remain low as no egg/follicle would mature
- LH levels remain low so ovulation would not occur
- Progesterone inhibits FSH/LH
- Progesterone levels remain high to maintain the lining of the uterus
- High levels of oestrogen build/maintain the lining of the uterus
- During early pregnancy, the placenta eventually takes over producing progesterone and oestrogen to maintain the pregnancy, rather than relying solely on the ovary
- This is why a maintained high level of progesterone across a full cycle, rather than the usual rise-and-fall pattern, is a key sign used in this style of question
Traps examiners saw
- Describing the normal cycle again (FSH rises, LH surges) rather than explaining what is DIFFERENT if pregnancy occurred, which is what the question specifically asks for
Full-mark self-check 0 of 4
The method for every Q7/Q6/Q8 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Linking FSH to follicle/egg maturation AND oestrogen release, then oestrogen to the LH surge, in the correct causal order
- Explaining hormone changes as a consequence of pregnancy (progesterone/oestrogen staying high to maintain the uterus lining) rather than describing the normal cycle again
- Comparing blood test results against the normal range with a stated conclusion, not just reading off numbers
The steps
- Always state the causal chain in order: FSH first (egg maturation, oestrogen release), then LH (triggered by high oestrogen, causes ovulation)
- For pregnancy-comparison questions, explain WHY levels are different (progesterone/oestrogen inhibiting FSH/LH, maintaining the uterus lining), not just 'they change'
- For blood-test comment questions, name each abnormal result, compare explicitly to the normal range, and state the likely biological cause
Which response does adrenaline prepare the body for?
Menstrual cycle questions want the FULL causal chain between hormones, in the right order, not each hormone described in isolation.
Practise hormones and the menstrual cycle“Explain how hormones in the combined contraceptive pill reduce the chance of pregnancy”
Both sittings test the mechanism of hormonal contraception, requiring the inhibition pathway rather than just naming the hormones involved.
1×asked“The combined contraceptive pill contains artificial versions of oestrogen and progesterone. Explain how the combined contraceptive pill prevents pregnancy.”
“The combined contraceptive pill contains artificial versions of oestrogen and progesterone. Explain how the combined contraceptive pill prevents pregnancy.”
What it’s really asking
It wants the hormonal inhibition mechanism: the artificial oestrogen and progesterone inhibit FSH and/or LH, preventing follicle maturation and ovulation.
The full worked answer — June 2022
The artificial oestrogen and progesterone in the combined pill inhibit the production of FSH, which prevents an egg or follicle from maturing in the ovary.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise contraceptionWhat the mark scheme rewarded
- Inhibits (the production of) FSH
- Which prevents (maturation of a follicle/ovulation)
- OR inhibits LH, so ovulation is prevented
- OR thickens cervical mucus (to stop sperm reaching the egg), or thins the uterus lining (reducing implantation chance)
- The combined pill contains both artificial oestrogen and progesterone, unlike the progesterone-only pill, and works mainly by suppressing the natural hormone signals that trigger ovulation
- Without ovulation, there is no egg available to be fertilised, which is the core reason the pill prevents pregnancy
Traps examiners saw
- Saying 'it stops pregnancy' without stating the specific hormone inhibited (FSH or LH) and its specific consequence, which is what actually earns the marks
Full-mark self-check 0 of 2
1×asked“When taken correctly, the combined pill can be over 99% effective. Taking the combined pill can lead to weight gain. Give one other disadvantage of using the combined pill as the only method of contraception.”
“When taken correctly, the combined pill can be over 99% effective. Taking the combined pill can lead to weight gain. Give one other disadvantage of using the combined pill as the only method of contraception.”
What it’s really asking
It wants a genuine disadvantage other than weight gain, most commonly that it does not protect against sexually transmitted infections.
The full worked answer — June 2022
The combined contraceptive pill does not protect against sexually transmitted infections.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise contraceptionWhat the mark scheme rewarded
- Doesn't prevent STIs (accept named STIs)
- OR still a chance of pregnancy (if taken incorrectly)
- Barrier methods such as condoms are needed alongside hormonal contraception if protection against sexually transmitted infections is also required
- Other disadvantages sometimes credited include remembering to take it daily and possible side effects such as mood changes or headaches
Traps examiners saw
- Repeating weight gain in a different wording, since the question specifically asks for one OTHER disadvantage
Full-mark self-check 0 of 1
The method for every Q7/Q6 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Naming which hormone (FSH or LH) is inhibited and the specific consequence (no egg maturation or no ovulation)
- Recognising a genuine disadvantage of hormonal contraception beyond the named one already given in the question
The steps
- State which hormone is inhibited (FSH or LH) as the first part of the answer
- Link the inhibition to its specific consequence: no follicle maturation (FSH) or no ovulation (LH), not just 'prevents pregnancy'
- For disadvantages, avoid repeating anything already given in the question stem
Which hormone triggers the release of an egg from the ovary (ovulation)?
Contraception questions want the specific hormone inhibited and its consequence, not just 'it stops pregnancy'.
Practise contraception“Explain how alveoli structure and Fick's law maximise gas exchange”
All three sittings test gas exchange in the lungs, linking alveoli/capillary structure to Fick's law factors (surface area, diffusion distance, concentration gradient).
1×asked“Explain why these alveoli have the internal structure shown.”
“Explain why these alveoli have the internal structure shown.”
What it’s really asking
It wants the alveoli's many-chambered structure linked to increased surface area, which maximises diffusion of gases into the capillaries.
What the sources actually showed — June 2019
A diagram of a cluster of alveoli connected to a bronchiole, with labelled blood vessels showing the pulmonary artery bringing blood in and the pulmonary vein taking blood away.
The full worked answer — June 2019
The alveoli are structured as many small chambers, or air sacs, clustered together, which greatly increases the total surface area available for gas exchange.
This large surface area maximises the rate of diffusion of oxygen from the alveoli into the surrounding capillaries, and of carbon dioxide in the opposite direction.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise gas exchangeWhat the mark scheme rewarded
- The structure shows many chambers/circles/alveoli (accept air sacs)
- Which increase the surface area (accept surface area to volume ratio)
- To maximise diffusion (from the alveoli into the capillaries) (accept more efficient gas exchange, or thin walls/membranes so a short diffusion distance)
- Alveoli also have moist, thin walls that are only one cell thick, further reducing the diffusion distance for gases, alongside their large surface area
- The dense network of capillaries surrounding each alveolus maintains a steep concentration gradient by constantly carrying oxygenated blood away and bringing deoxygenated blood in
Traps examiners saw
- Describing the structure without linking it explicitly to increased surface area or diffusion, a bare description without the Fick's law link does not earn full marks
Full-mark self-check 0 of 3
1×asked“The capillary wall is only one cell thick. Explain how gases move from the alveolus to the capillary.”
“The capillary wall is only one cell thick. Explain how gases move from the alveolus to the capillary.”
What it’s really asking
It wants the three-part diffusion chain: movement by diffusion, down a concentration gradient, through the one-cell-thick membrane.
What the sources actually showed — June 2023
A cross-section diagram of an alveolus and an adjacent capillary, with the alveolar wall, capillary wall and a red blood cell inside the capillary all labelled.
The full worked answer — June 2023
Gases move from the alveolus to the capillary by diffusion.
They move down a concentration gradient, from a high concentration in the alveolus to a lower concentration in the capillary.
This diffusion happens through the thin membrane formed by the alveolar wall and the capillary wall, both of which are only one cell thick.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise gas exchangeWhat the mark scheme rewarded
- By diffusion
- Down a concentration gradient/from high to low concentration
- Through a membrane
- Oxygen diffuses from the alveolus (high concentration, just breathed in) into the capillary (low concentration, since it has been used up by respiring cells)
- Carbon dioxide diffuses in the opposite direction, from the capillary (high concentration, produced by respiration) into the alveolus (low concentration, ready to be breathed out)
Traps examiners saw
- Naming osmosis or active transport instead of diffusion, gases move passively down their own concentration gradient, they do not require energy or involve water specifically
Full-mark self-check 0 of 3
The method for every Q9/Q6 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Naming the specific structural feature (large surface area, thin walls, dense capillary network) AND linking it to a named Fick's law factor
- Explaining WHY a one-cell-thick membrane or single-file red blood cell flow maximises diffusion, not just describing the structure
The steps
- For 'why is the structure like this', always name the Fick's law factor the structure improves: surface area, diffusion distance, or concentration gradient
- For 'how do gases move', give diffusion, direction (high to low concentration), and the membrane it crosses, as three separate points
- For single-file red blood cell questions, link the narrow capillary to slower flow, more time for diffusion, and maximising oxygen uptake
Which is the correct order of structures air passes through to reach the lungs?
Gas exchange questions always link structure to a named Fick's law factor. Practise stating WHY, not just describing WHAT.
Practise gas exchange“State two differences between aerobic and anaerobic respiration, and explain a hydrogencarbonate indicator result”
Both sittings we have full data for test respiration directly, comparing aerobic and anaerobic respiration and interpreting carbon dioxide indicator results from a practical-style investigation.
1×asked“When the athlete is running, their muscle cells use both aerobic respiration and anaerobic respiration. State two differences between aerobic respiration and anaerobic respiration.”
“When the athlete is running, their muscle cells use both aerobic respiration and anaerobic respiration. State two differences between aerobic respiration and anaerobic respiration.”
What it’s really asking
It wants two genuinely distinct differences, most safely: oxygen use, and either energy released or the specific products formed.
The full worked answer — June 2023
Aerobic respiration uses oxygen, whereas anaerobic respiration does not use oxygen.
Aerobic respiration also releases more energy than anaerobic respiration, and produces carbon dioxide and water as products, whereas anaerobic respiration in muscle cells produces lactic acid instead.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise respirationWhat the mark scheme rewarded
- Aerobic respiration uses oxygen/anaerobic does not use oxygen
- Aerobic respiration releases more energy/anaerobic releases less energy
- Aerobic produces carbon dioxide/water; anaerobic produces lactic acid (accept lactate)
- Aerobic respiration takes place in the mitochondria/anaerobic takes place in the cytoplasm
- During intense exercise, muscle cells cannot get enough oxygen delivered quickly enough, so they switch partly to anaerobic respiration to keep releasing energy
- Lactic acid build-up from anaerobic respiration is linked to muscle fatigue and the drop in muscle pH seen after intense exercise
Traps examiners saw
- Giving two differences from the same category, for example 'aerobic uses oxygen' and 'anaerobic does not use oxygen' counted only once as a single credited difference, not two
Full-mark self-check 0 of 2
1×asked“A scientist placed pondweed into two sealed test tubes containing green BTB solution. Test tube A was kept in the dark. Test tube B was kept in the light. Explain the results for tube A and tube B.”
“A scientist placed pondweed into two sealed test tubes containing green BTB solution. Test tube A was kept in the dark. Test tube B was kept in the light. Explain the results for tube A and tube B.”
What it’s really asking
It wants tube A (dark) explained by respiration alone producing carbon dioxide, turning the indicator yellowy-green, and tube B (light) explained by photosynthesis balancing out respiration, keeping the indicator green.
What the sources actually showed — June 2023
Two identical sealed test tubes, each containing pondweed in green BTB solution, one labelled 'A in dark' and the other labelled 'B in light'.
A table showing the colour of the BTB solution in each tube after 5 hours: tube A is yellowy green, tube B remains green.
| Test tube | Colour of BTB solution after 5 hours |
|---|---|
| A (kept in the dark) | Yellowy green |
| B (kept in the light) | Green |
The full worked answer — June 2023
In tube A, kept in the dark, the pondweed could only respire, since no light was available for photosynthesis, so it produced carbon dioxide, which made the BTB solution turn yellowy green.
In tube B, kept in the light, the pondweed carried out photosynthesis as well as respiration, using up the carbon dioxide produced by respiration, so the overall carbon dioxide level stayed balanced and the indicator remained green.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise respirationWhat the mark scheme rewarded
- Tube A: respiration took place, producing carbon dioxide/photosynthesis did not take place
- Tube B: photosynthesis took place, using up the carbon dioxide
- BTB (bromothymol blue) solution turns yellow as carbon dioxide dissolves and forms a weak acid, and returns to blue/green as carbon dioxide is removed
- A plant kept in the light photosynthesises and respires simultaneously, so a lack of colour change indicates the two processes are roughly balanced
Traps examiners saw
- Saying 'tube B did not respire' rather than the more accurate 'tube B's photosynthesis used up the carbon dioxide that respiration produced', since respiration still occurs in the light, it is just balanced out
Full-mark self-check 0 of 2
The method for every Q3/Q3 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Giving two genuinely distinct differences between aerobic and anaerobic respiration (oxygen use, energy released, and/or products), not two versions of the same point
- Explaining an indicator colour change by linking the organism's activity (respiring or not) to the amount of carbon dioxide produced
The steps
- For differences, pick two DIFFERENT categories (oxygen use, energy amount, or product), not two ways of saying 'anaerobic makes less energy'
- For indicator questions, always state which specific organism respired (producing carbon dioxide, turning indicator yellow) and which did not (staying red/green)
- Distinguish germinating from dried peas: only living, respiring tissue produces carbon dioxide
Where in the cell does aerobic respiration take place?
Respiration questions want genuinely distinct differences and clear reasoning about which process is happening. Learn to avoid restating the same point twice.
Practise respiration“Calculate light intensity using the inverse square law and explain limiting factors in photosynthesis”
Both sittings we have full data for use real light-intensity or gas-production data, requiring either a calculation using the inverse square law or an explanation of why a gas stopped being produced.
1×asked“The light intensity was calculated using the inverse square law for photosynthesis. Calculate the light intensity at a distance of 25 cm from the lamp. Include the equation for the inverse square law in your answer.”
“The light intensity was calculated using the inverse square law for photosynthesis. Calculate the light intensity at a distance of 25 cm from the lamp. Include the equation for the inverse square law in your answer.”
What it’s really asking
It wants the equation light intensity is proportional to 1 over distance squared, correctly substituted with 25 cm, giving a final numerical answer.
What the sources actually showed — June 2023
A table showing distance from the lamp in centimetres, the number of bubbles of gas produced by pondweed in two minutes, and the calculated light intensity in arbitrary units, for five different distances.
| Distance from the lamp (cm) | Number of bubbles in two minutes | Light intensity (arbitrary units) |
|---|---|---|
| 5 | 62 | 0.04 |
| 10 | 60 | 0.01 |
| 15 | 43 | 0.0044 |
| 20 | 32 | 0.0025 |
| 25 | 11 | ? |
The full worked answer — June 2023
The inverse square law states that light intensity is proportional to 1 divided by the distance squared.
Substituting the distance of 25 cm: light intensity is proportional to 1 divided by 25 squared, which is 1 divided by 625.
This gives a light intensity of 0.0016 arbitrary units at 25 cm from the lamp.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise photosynthesisWhat the mark scheme rewarded
- States the equation: light intensity is proportional to 1 divided by distance squared
- Correct substitution: 1 divided by (25 squared, or 625)
- Final answer of 0.0016 (arbitrary units); correct answer with no working also earns full marks
- The inverse square law explains why light intensity falls away very quickly as a light source is moved further from an object, since the intensity depends on distance squared, not distance alone
- This is the same relationship used in the required practical investigating light intensity and the rate of photosynthesis in pondweed
Traps examiners saw
- Forgetting to square the distance before dividing, giving 1 divided by 25 (0.04) instead of 1 divided by 625 (0.0016), a factor-of-25 error
Full-mark self-check 0 of 3
1×asked“Joseph Priestley continued the investigation but placed a plant inside the bell jar. State why the candle was not burning after three minutes.”
“Joseph Priestley continued the investigation but placed a plant inside the bell jar. State why the candle was not burning after three minutes.”
What it’s really asking
It wants the reason the candle went out: all the oxygen inside the sealed bell jar had been used up by the burning candle.
What the sources actually showed — June 2019
Two diagrams showing a lit candle sealed inside a bell jar over a dish of water, one labelled 'candle sealed in a bell jar' and the other 'candle after 3 minutes', showing the flame extinguished.
The full worked answer — June 2019
All of the oxygen inside the sealed bell jar had been used up, so there was no oxygen left for the candle to keep burning.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise photosynthesisWhat the mark scheme rewarded
- All the oxygen had been used up/no oxygen left
- This experiment is based on Joseph Priestley's historical demonstration, one of the earliest investigations linking green plants to the oxygen needed for combustion
- Because the bell jar is sealed, no new oxygen can enter to replace what the candle's combustion consumes
Traps examiners saw
- Saying 'the candle ran out of wax' or an unrelated physical explanation, the sealed-container oxygen depletion is the specific biological/chemical reasoning the mark scheme rewards
Full-mark self-check 0 of 1
The method for every Q10/Q5 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Correctly stating and applying the inverse square law equation (light intensity is proportional to 1 divided by distance squared)
- Explaining WHY a plant stopped producing oxygen, linking it to a resource (carbon dioxide, oxygen already present) being used up
The steps
- Always state the inverse square law equation first (1 divided by distance squared) before substituting numbers
- Square the distance correctly before dividing, this is the step most likely to go wrong under time pressure
- For 'why did production stop' questions, name the resource that ran out rather than a vague 'conditions changed'
Where does photosynthesis take place in plant cells?
Photosynthesis calculation questions want the equation stated before you substitute. Practise the inverse square law step by step.
Practise photosynthesis“Explain how air flow affects transpiration rate, using xylem and phloem structure”
Both sittings test plant transport structures directly, either describing xylem/phloem features or explaining how an environmental factor changes the rate of water uptake.
1×asked“Describe two features of the structure of xylem vessels that can be seen in the figure.”
“Describe two features of the structure of xylem vessels that can be seen in the figure.”
What it’s really asking
It wants two genuine visible structural features of xylem: thick walls, and continuous hollow tubes without end walls.
What the sources actually showed — June 2022
A diagram of a plant stem with a magnified cross-section showing the xylem and phloem tissue side by side, with arrows indicating the direction of water movement in the xylem and sucrose movement in the phloem.
The full worked answer — June 2022
Xylem vessels have thick cell walls, which help support the plant and withstand the pressure of water moving through them.
They are also made up of continuous, hollow tubes with no end walls between the cells, allowing water to flow through them easily from the roots to the leaves.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise plant transportWhat the mark scheme rewarded
- Thick walls
- Continuous/hollow tubes/no end walls (accept no cytoplasm, accept made of lignin/dead cells)
- Xylem vessels are made of dead cells joined end to end, with the internal cross-walls broken down to form a continuous tube, unlike phloem which retains living cytoplasm
- The thick walls are strengthened with a substance called lignin, which also gives plant stems their rigidity
Traps examiners saw
- Describing phloem features (living cells, sucrose transport) when the question specifically asks about xylem, these are opposite tissue types with different structures
Full-mark self-check 0 of 2
1×asked“Explain why switching on the fan caused a change in the volume of water taken up by the plant.”
“Explain why switching on the fan caused a change in the volume of water taken up by the plant.”
What it’s really asking
It wants the full chain: the fan increases air flow across the leaf, removing water vapour, which increases the rate of evaporation/transpiration, causing the plant to take up more water.
What the sources actually showed — June 2022
A line graph showing the cumulative volume of water taken up by a plant over 10 minutes, comparing a line where a fan was switched on after 3 minutes against a line where the fan was never switched on.
The full worked answer — June 2022
Switching on the fan causes air to move across the leaf surface, creating wind or increased air flow.
This moving air removes the water vapour that builds up around the leaf, which increases the rate of diffusion and evaporation of water vapour from the leaf's stomata.
As transpiration increases, the plant takes up more water from its roots through the xylem to replace the water lost, which explains the steeper increase in the volume of water taken up once the fan was switched on.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise plant transportWhat the mark scheme rewarded
- Fan causes air to move/creates wind/increased air flow
- Water (vapour) removed (from around the leaf)
- Increased rate of diffusion/evaporation/transpiration (of water vapour from the leaf)
- Causing the plant to take up more water
- Transpiration is the loss of water vapour from a plant's leaves, mostly through the stomata, and it creates a 'pull' that draws more water up through the xylem from the roots
- A still, humid environment slows transpiration because water vapour builds up around the leaf and reduces the concentration gradient driving diffusion out of the stomata
Traps examiners saw
- Jumping straight to 'more water is taken up' without explaining the mechanism in between (vapour removed, increased evaporation rate), which is what the marks are actually awarded for
Full-mark self-check 0 of 4
The method for every Q5/Q2 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Naming genuine structural features of xylem (thick walls, continuous hollow tubes) rather than confusing it with phloem
- Building the full transpiration chain: air movement, water vapour removed, increased evaporation/diffusion rate, more water taken up
The steps
- For xylem structure, focus on the physical features visible in a diagram: wall thickness and tube continuity, not its function
- For air-flow questions, build the chain in order: air movement, vapour removed, transpiration rate increases, water uptake increases
- Distinguish xylem (water, thick dead cell walls) from phloem (sucrose, living cells) clearly
Which substance does xylem tissue transport?
Plant transport questions want the full transpiration chain explained, and xylem/phloem structural features kept clearly distinct.
Practise plant transport“Explain the commercial uses of auxins, gibberellins and ethene in plant and fruit production”
This is a 6-mark, asterisked extended-response question in the sitting we have it, marked against a 3-level scheme rewarding coverage of all three named hormones.
1×asked“Explain the uses of auxins, gibberellins and ethene in the commercial production of plants and fruits.”
“Explain the uses of auxins, gibberellins and ethene in the commercial production of plants and fruits.”
What it’s really asking
It wants a genuine commercial use for each of the three named hormones, each linked to the specific process or growth stage it affects, covering weedkillers/rooting powder, seed germination/seedless fruit, and fruit ripening respectively.
The full worked answer — June 2022
Auxins are used commercially as selective weedkillers. They are absorbed by broad-leaved weeds far more than by narrow-leaved crop plants such as cereals, so spraying a field with auxin-based weedkiller causes uncontrolled, excessive growth in the weeds that kills them, while leaving the narrow-leaved crop largely unaffected.
Auxins are also used in rooting powder, which is applied to the cut end of a plant cutting to stimulate the growth of new roots, allowing gardeners and growers to produce new plants quickly and reliably from cuttings.
Gibberellins are used commercially to stimulate germination in seeds that would otherwise stay dormant, by initiating the breakdown of starch stores inside the seed to provide energy for the embryo to begin growing. Gibberellins are also sprayed onto some plants before pollination to stimulate the development of seedless fruit, which is commercially valuable because consumers often prefer fruit without seeds.
Ethene is used commercially to ripen fruit. Fruit such as bananas are often picked while still unripe so that they survive being transported long distances without becoming damaged, and ethene gas is then applied once the fruit has reached its destination, ripening it so it is ready for sale.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise plant hormonesWhat the mark scheme rewarded
- Auxins: used in selective weed killers, targeting broad leaf plants and not narrow leaf crops; used as rooting powder, added to cuttings to stimulate root growth
- Gibberellins: stimulate germination in dormant seeds by initiating the breakdown of starch; stimulate flower formation; promote fruit formation; sprayed onto plants before pollination; stimulate development of seedless fruits
- Ethene: used in fruit ripening; unripe fruit is harvested (for transport); ethene is added so the fruit ripens in time for selling
- Level 3 (5 to 6 marks) requires identification of commercial uses of ALL THREE hormones, each linked to the process involved or when it is used
- Auxins are naturally produced at the tip of a growing shoot and control the plant's response to light (phototropism) and gravity (gravitropism), which is why they can be exploited to control weed growth
- Ethene is a gas at room temperature, unlike auxins and gibberellins, which is why it can be applied to whole storage rooms of fruit at once to trigger ripening
Traps examiners saw
- Only covering two of the three hormones in detail, which caps the answer at Level 2 even if those two are explained thoroughly
- Naming a hormone's use without linking it to the process or timing involved, for example just writing 'ethene ripens fruit' without explaining the unripe-harvest-then-ripen commercial reasoning
Full-mark self-check 0 of 4
The method for every Q7 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Naming a genuine commercial use for EACH of the three hormones (auxins, gibberellins, ethene), not just one or two
- Linking each use to the specific process or stage of growth it affects, not just naming the hormone
The steps
- Structure the answer in three clear sections, one per hormone, so no hormone is accidentally missed
- For auxins, cover selective weedkillers and rooting powder as the two most commonly rewarded uses
- For gibberellins, cover breaking seed dormancy/germination and producing seedless fruit
- For ethene, cover fruit ripening, specifically ripening fruit picked unripe for transport
When a plant shoot is lit from one side, where does auxin accumulate?
Plant hormone questions want all three hormones covered with a linked commercial use each. Structure your answer in three clear sections.
Practise plant hormones“Calculate net carbon movement into the atmosphere and describe how carbon is cycled through living and non-living components”
Both sittings we have full data for test the carbon cycle in depth, from a numerical net-carbon calculation through to a full extended-response description of biotic and abiotic carbon movement.
1×asked“Calculate the net mass of carbon added to the atmosphere each year.”
“Calculate the net mass of carbon added to the atmosphere each year.”
What it’s really asking
It wants the total carbon released into the atmosphere (respiration plus combustion plus ocean loss) minus the total carbon absorbed (photosynthesis plus ocean uptake), giving the net change.
What the sources actually showed — June 2019
A table showing five processes (photosynthesis, respiration, ocean uptake, ocean loss, combustion of fossil fuels) with the mass of carbon moved into or out of the atmosphere each year, in gigatonnes.
| Process | Mass of carbon moved into/out of the atmosphere (gigatonnes per year) |
|---|---|
| Photosynthesis | 120.1 |
| Respiration | 119.6 |
| Ocean uptake | 92.8 |
| Ocean loss | 90 |
| Combustion of fossil fuels | 6.4 |
The full worked answer — June 2019
Carbon released into the atmosphere comes from respiration (119.6), ocean loss (90.0) and combustion of fossil fuels (6.4), giving a total of 216.0 gigatonnes released.
Carbon absorbed from the atmosphere comes from photosynthesis (120.1) and ocean uptake (92.8), giving a total of 212.9 gigatonnes absorbed. The net mass of carbon added to the atmosphere is therefore 216.0 minus 212.9, which equals 3.1 gigatonnes.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise the carbon cycleWhat the mark scheme rewarded
- Carbon absorbed: 120.1 + 92.8 = 212.9 (or carbon released: 119.6 + 90 + 6.4 = 216.0)
- Evaluation: net figure of 3.1 gigatonnes; award full marks for correct answer with no working
- This kind of question tests whether carbon in the atmosphere is increasing or decreasing overall, by comparing all the processes that add carbon against all the processes that remove it
- A positive net figure like 3.1 gigatonnes shows the atmosphere is gaining carbon overall, consistent with rising global atmospheric carbon dioxide levels
Traps examiners saw
- Mixing up which values go into 'absorbed' versus 'released', photosynthesis and ocean uptake both remove carbon FROM the atmosphere, while respiration, ocean loss and combustion all add carbon TO it
Full-mark self-check 0 of 3
1×asked“Describe how carbon is cycled through the biotic and abiotic components of an ecosystem.”
“Describe how carbon is cycled through the biotic and abiotic components of an ecosystem.”
What it’s really asking
It wants a detailed description covering plants, animals and decomposers (biotic) and at least one abiotic process such as combustion or ocean exchange, linked to respiration and photosynthesis specifically.
The full worked answer — June 2023
In the biotic environment, plants take in carbon dioxide from the atmosphere during photosynthesis and convert it into carbon-containing compounds such as glucose, which are stored in the plant's tissues. Plants also release carbon dioxide back into the atmosphere through their own respiration.
When animals eat plants, or eat other animals, the carbon-containing compounds are passed along the food chain, and animals release carbon dioxide back into the atmosphere through their own respiration.
When plants and animals die, decomposers break down their remains and release carbon dioxide back into the atmosphere through their own respiration as they feed on the dead material.
In the abiotic environment, the combustion of fossil fuels releases stored carbon dioxide back into the atmosphere, while the oceans can also absorb carbon dioxide directly from the atmosphere, and carbon can be locked away for long periods in carbonate rocks, which release carbon dioxide again slowly through erosion or more suddenly through volcanic activity.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise the carbon cycleWhat the mark scheme rewarded
- Biotic, plants: photosynthesis takes in carbon dioxide; plants store carbon compounds (e.g. glucose); respiration releases carbon dioxide; carbon transferred to animals when eaten
- Biotic, animals: release carbon dioxide when they respire; ingest carbon compounds when they eat plants or other animals
- Biotic, decomposers: release carbon dioxide during respiration; break things down
- Abiotic: burning fossil fuels releases carbon dioxide/particulates; oceans can absorb carbon dioxide; carbon stored in carbonate rocks; erosion of carbonate rocks releases carbon dioxide; volcanoes release carbon dioxide
- Level 3 (5 to 6 marks) requires a detailed description of BOTH biotic and abiotic components, including the role of plants, animals and decomposers, linked to respiration, photosynthesis and an abiotic process
- The carbon cycle links the living (biotic) and non-living (abiotic) parts of the planet together, showing that the same carbon atoms are continually recycled rather than created or destroyed
- Fossil fuels themselves formed from the compressed, partially decomposed remains of ancient plants and animals over millions of years, which is why burning them releases carbon that had been locked away for a very long time
Traps examiners saw
- Only describing the biotic side (plants, animals, decomposers) and never mentioning an abiotic process at all, which caps the answer at Level 2 regardless of how detailed the biotic section is
- Naming decomposers without explaining that they specifically release carbon dioxide through their OWN respiration, rather than just 'breaking things down'
Full-mark self-check 0 of 4
The method for every Q10/Q9 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Correctly identifying which values represent carbon entering versus leaving the atmosphere before calculating the net figure
- Covering ALL THREE biotic roles (plants, animals, decomposers) AND at least one abiotic process (fossil fuel combustion, ocean exchange, or carbonate rock weathering)
The steps
- For calculation questions, separate the given values into 'carbon into the atmosphere' and 'carbon out of the atmosphere' before subtracting
- For the extended description, structure your answer as: plants (photosynthesis in, respiration out), animals (eating, respiration out), decomposers (respiration out from decay), then abiotic (combustion, ocean, rock)
- Do not stop at only the biotic side, since Level 3 explicitly requires an abiotic process too
Which process removes CO₂ from the atmosphere?
Carbon cycle extended questions want BOTH the biotic roles (plants, animals, decomposers) AND an abiotic process. Missing the abiotic half caps your level.
Practise the carbon cycle“Describe the roles of decomposing, nitrifying, nitrogen-fixing and denitrifying bacteria”
All three sittings test the nitrogen cycle, always through the specific roles of the different named types of bacteria involved.
1×asked“Nitrogen is cycled through the environment. Describe the roles of bacteria in the nitrogen cycle.”
“Nitrogen is cycled through the environment. Describe the roles of bacteria in the nitrogen cycle.”
What it’s really asking
It wants the roles of the different bacteria named in sequence: decomposers producing ammonia, nitrifying bacteria converting ammonia to nitrates, nitrogen-fixing bacteria converting atmospheric nitrogen to nitrates, and denitrifying bacteria releasing nitrogen back into the atmosphere.
The full worked answer — June 2019
Decomposers break down waste matter, such as dead organisms, releasing the nitrogen compounds within them as ammonia.
Nitrifying bacteria then convert this ammonia into nitrites and then nitrates, which plants can absorb through their roots.
Nitrogen-fixing bacteria convert nitrogen gas from the atmosphere directly into nitrates, providing another route by which nitrates enter the soil.
Denitrifying bacteria do the opposite, converting nitrates in the soil back into nitrogen gas, which is released back into the atmosphere.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise the nitrogen cycleWhat the mark scheme rewarded
- Decomposers break down waste matter (into ammonia) (accept dead organisms for waste matter)
- Nitrifying bacteria convert ammonia/nitrifying bacteria make nitrites/nitrates (accept nitrification)
- Nitrogen-fixing bacteria convert nitrogen into nitrates (accept ammonia/nitrogen compounds for nitrates)
- Denitrifying bacteria convert nitrates/release nitrogen (accept denitrification releases nitrogen)
- Nitrogen-fixing bacteria can live freely in the soil or in a mutualistic relationship inside root nodules of leguminous plants such as peas and beans, which is why crop rotation with legumes helps restore soil fertility
- Denitrifying bacteria are more active in waterlogged soils with low oxygen levels, which is one reason overwatering can reduce nitrate availability for crops
Traps examiners saw
- Confusing nitrifying bacteria (ammonia to nitrates) with nitrogen-fixing bacteria (atmospheric nitrogen to nitrates), these are two separate credited roles with different starting materials
- Forgetting denitrifying bacteria entirely, since three correct roles named still misses this fourth, oppositely-acting bacterial type
Full-mark self-check 0 of 4
1×asked“Explain how crop rotation increases nitrate levels in the soil.”
“Explain how crop rotation increases nitrate levels in the soil.”
What it’s really asking
It wants the specific mechanism: leguminous crops are planted, which have nitrogen-fixing bacteria in root nodules that convert atmospheric nitrogen into nitrates in the soil.
What the sources actually showed — June 2022
A microscope image of a cross-section of a root nodule on a leguminous plant, with bacteria inside the nodule labelled.
A simple flow diagram showing dead animals and plants converted to ammonia (process X), then ammonia converted to nitrates (process Y).
The full worked answer — June 2022
In crop rotation, leguminous crops such as peas or beans are planted in the field for one growing season.
These leguminous plants have nitrogen-fixing bacteria living inside nodules in their roots.
These bacteria fix nitrogen gas from the atmosphere, converting it into nitrates that are added to the soil, increasing the nitrate levels available for future crops planted in the same field.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise the nitrogen cycleWhat the mark scheme rewarded
- Leguminous crops planted (accept named leguminous crops)
- That have nitrogen-fixing bacteria in root (nodules)
- Which fix nitrogen (gas) (accept use nitrogen from the air/use atmospheric nitrogen/make ammonia; ignore 'produce nitrates')
- Crop rotation involves growing different types of crop in a field across successive seasons, rather than growing the same crop repeatedly, which would otherwise deplete soil nitrates
- The relationship between the legume and the nitrogen-fixing bacteria is mutualistic, since the plant provides the bacteria with sugars from photosynthesis in exchange for nitrogen compounds
Traps examiners saw
- Saying the plant itself 'produces nitrates' rather than crediting the bacteria living in its root nodules, which is the organism actually responsible for nitrogen fixation
Full-mark self-check 0 of 3
The method for every Q10/Q5/Q9 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Naming the correct TYPE of bacteria for each named stage (decomposing, nitrifying, nitrogen-fixing, denitrifying), not mixing them up
- Stating the specific chemical conversion each type carries out (ammonia to nitrates, atmospheric nitrogen to nitrates, nitrates back to atmospheric nitrogen)
The steps
- Keep the four bacterial roles separate in your mind: decomposing (waste to ammonia), nitrifying (ammonia to nitrates), nitrogen-fixing (air's nitrogen to nitrates), denitrifying (nitrates back to air's nitrogen)
- Denitrifying bacteria are the one type that REDUCES the nitrates available to plants, the opposite direction to the other three
- For crop rotation/legume questions, name nitrogen-fixing bacteria specifically, living in root nodules
What percentage of the atmosphere is made up of nitrogen gas (N₂)?
Nitrogen cycle questions want each named type of bacteria kept distinct, decomposing, nitrifying, nitrogen-fixing, and denitrifying all play different roles.
Practise the nitrogen cycle“Explain where biodiversity will be highest in a polluted stream using indicator species and oxygen data”
Both sittings we have full data for use a real oxygen-concentration or pollution dataset along a stream, requiring indicator species knowledge to be linked to a biodiversity conclusion.
2×asked“Which indicator species would be most likely to be seen in the water at point A?”
“Which indicator species would be most likely to be seen in the water at point A?”
What it’s really asking
It wants the correct indicator species for heavily polluted, low-oxygen water, which is sludgeworm.
What the sources actually showed — June 2022
A description stating bloodworms found in a pond indicate that the water is polluted.
The full worked answer — June 2022
Sludgeworm.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise ecosystems and communitiesWhat the sources actually showed — June 2023
A diagram of a stream flowing past a fertiliser factory, with five labelled sampling points (A to E) along the direction of flow, plus a table showing oxygen concentration in parts per million at each point.
| Point along stream | Oxygen concentration (ppm) |
|---|---|
| A | 1.5 |
| B | 2.7 |
| C | 3.4 |
| D | 4.4 |
| E | 4.5 |
The full worked answer — June 2023
Sludgeworm.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise ecosystems and communitiesWhat the mark scheme rewarded
- The single correct answer: sludgeworm
- Indicator species can be used to assess water quality without needing chemical testing equipment, since different species have different tolerances to low oxygen and pollution
- Sludgeworm and bloodworm both tolerate very low oxygen levels because they contain haemoglobin, which helps them absorb what little oxygen is available
Traps examiners saw
- Selecting stonefly or freshwater shrimp, both of which require clean, highly oxygenated water and would not survive at the most polluted point
Full-mark self-check 0 of 1
1×asked“Explain where the biodiversity will be highest in the stream.”
“Explain where the biodiversity will be highest in the stream.”
What it’s really asking
It wants the specific location (furthest downstream from the factory) linked explicitly to the highest oxygen concentration recorded there, and the reason organisms can survive/respire in higher-oxygen water.
What the sources actually showed — June 2023
A diagram of a stream flowing past a fertiliser factory, with five labelled sampling points (A to E) along the direction of flow, plus a table showing oxygen concentration in parts per million at each point.
| Point along stream | Oxygen concentration (ppm) |
|---|---|
| A | 1.5 |
| B | 2.7 |
| C | 3.4 |
| D | 4.4 |
| E | 4.5 |
The full worked answer — June 2023
Biodiversity will be highest at point E, furthest downstream from the fertiliser factory, since this is the point furthest from the pollution.
This is because the oxygen concentration is highest here, at 4.5 parts per million, compared with the much lower concentrations recorded closer to the factory.
A wider range of organisms can survive and respire in water with more available oxygen, which is why more species, and therefore greater biodiversity, are found at this point in the stream.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise ecosystems and communitiesWhat the mark scheme rewarded
- There would be most biodiversity in the stream at point D to E/E/furthest from the factory (accept before the factory in the stream)
- As oxygen concentration is highest here (accept less pollution/waste here)
- So organisms can survive/respire
- Fertiliser runoff into water causes eutrophication, which reduces oxygen levels as algae and bacteria multiply and use up available oxygen, harming the organisms that need it
- As water flows further from a pollution source, some natural dilution and re-oxygenation typically occurs, which is why oxygen concentration was shown increasing steadily along the stream
Traps examiners saw
- Naming the wrong point, or simply saying 'downstream' without linking to the oxygen data value and the survival/respiration reasoning, all three parts are needed for full marks
Full-mark self-check 0 of 3
The method for every Q2/Q1 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Selecting the correct indicator species for the given pollution level from the data provided, not from memory alone
- Linking a data trend (oxygen concentration) to a biodiversity conclusion with a stated reason, not just describing the trend
The steps
- Learn the indicator species ladder: sludgeworm and bloodworm tolerate very low oxygen/high pollution; freshwater shrimp and stonefly need high oxygen/clean water
- For biodiversity questions, always name the specific point/location with the reasoning (highest oxygen, furthest from the pollution source), not just 'here is more biodiverse'
- Link the numerical data explicitly, quoting the relevant oxygen concentration value if given
What is a community in ecology?
Ecosystem and indicator species questions want the data linked explicitly to a biodiversity conclusion, not just a species name in isolation.
Practise ecosystems and communities“Explain how removing a species from a food web affects others, and how reforestation/conservation improves biodiversity”
Both sittings we have full data for test human impacts on ecosystems, from a real Antarctic food web disrupted by overfishing to an extended-response question on reforestation and animal conservation.
1×asked“Humans are removing large numbers of cod from the Antarctic Ocean. Explain why the removal of cod could lead to an increase in the numbers of squid and penguins.”
“Humans are removing large numbers of cod from the Antarctic Ocean. Explain why the removal of cod could lead to an increase in the numbers of squid and penguins.”
What it’s really asking
It wants the indirect mechanism: fewer cod means less competition for shrimps (the shared food source), so more shrimps are available for squid and penguins to eat.
What the sources actually showed — June 2023
A food web diagram of the Antarctic Ocean showing phytoplankton, shrimps, cod, squid, penguins and seals, with arrows showing feeding relationships between them.
The full worked answer — June 2023
Cod, squid and penguins all feed on shrimps, so removing cod from the food web reduces the competition for shrimps as a food source.
This means fewer shrimps are eaten by cod, so more shrimps are available for squid and penguins to eat, allowing their populations to increase.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise human impacts on biodiversityWhat the mark scheme rewarded
- Less competition for food (for penguins and squid)
- Because fewer shrimps will be eaten by the cod/more shrimps available/more food available
- In a food web, species can be linked both directly (predator-prey) and indirectly (through shared food sources), which is why removing one species can have effects on others it never directly interacts with
- Overfishing large predatory or mid-level fish species such as cod can cause knock-on effects throughout an entire marine ecosystem, not just to the species being fished
Traps examiners saw
- Only stating 'squid and penguins have less competition' without naming the SHARED FOOD SOURCE (shrimps) that links cod, squid and penguins together, which is the specific mechanism the mark scheme wants
Full-mark self-check 0 of 2
1×asked“Reforestation has a beneficial effect on air composition and biodiversity. Animal conservation projects can also have a beneficial effect on biodiversity. Explain the beneficial effects of reforestation and animal conservation projects.”
“Reforestation has a beneficial effect on air composition and biodiversity. Animal conservation projects can also have a beneficial effect on biodiversity. Explain the beneficial effects of reforestation and animal conservation projects.”
What it’s really asking
It wants detailed, linked coverage of BOTH reforestation (habitats, atmospheric gases via photosynthesis) AND animal conservation (protecting endangered species, maintaining food webs and genetic diversity).
The full worked answer — June 2022
Reforestation is the planting of trees on land where forest has been removed. As the trees grow, they increase the rate of photosynthesis taking place, which removes carbon dioxide from the atmosphere and releases oxygen, helping to reduce the greenhouse effect and global warming caused by excess atmospheric carbon dioxide.
Reforestation also provides new habitats for animals to live in, and the trees themselves can be a source of food, or renewable resources for humans, and their roots help prevent soil erosion and reduce flooding by taking up water from the soil.
Animal conservation projects, such as controlled breeding programmes in zoos or animal parks, increase the numbers of endangered species and help prevent them from becoming extinct.
These projects can also generate income through ecotourism to fund further conservation work, and by maintaining genetic diversity and food webs, allowing animals to eventually be reintroduced into the wild once their populations have recovered.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise human impacts on biodiversityWhat the mark scheme rewarded
- Reforestation: is the planting of trees; trees take up water from the soil; prevents erosion and reduces flooding; trees can be used for renewable resources; provides habitats; increases the rate of photosynthesis; removes carbon dioxide and releases oxygen; reduces greenhouse gases/global warming; provides a source of medicines/food for consumers
- Animal conservation: increases numbers of endangered species/prevents extinction; through controlled breeding programmes/reduction in poaching/maintaining habitats; generating income to fund conservation projects through zoos/animal parks/ecotourism; improves the number of animals/range of species; maintains the food web; maintains genetic diversity; allows re-introduction of animals into the wild
- Level 3 (5 to 6 marks) requires a detailed explanation of the benefits of BOTH reforestation and animal conservation, referencing changes in named atmospheric gases AND how animal conservation improves biodiversity, including why endangered species are preserved or the impact on food webs
- Deforestation is a major driver of biodiversity loss globally, since it destroys habitats faster than most species can adapt or relocate, which is why reforestation is used to try to reverse this damage
- Captive breeding programmes have successfully helped recover the wild populations of some critically endangered species, though reintroduction success varies depending on the species and its remaining habitat
Traps examiners saw
- Only explaining reforestation OR only explaining animal conservation in detail, with the other topic barely mentioned, which caps the answer below Level 3 even if one half is excellent
- Naming carbon dioxide and oxygen changes without linking them explicitly to photosynthesis, since the top level specifically wants the named atmospheric gases connected to the process causing the change
Full-mark self-check 0 of 4
The method for every Q9/Q7 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Correctly reasoning through a food web using competition and predation, not just 'numbers will change'
- Covering BOTH reforestation AND animal conservation with named atmospheric/biodiversity benefits, for the extended-response version
The steps
- For food web questions, trace the SPECIFIC path of effect (who eats what, who competes with whom) rather than a general statement
- Distinguish direct effects (less predation, more prey) from indirect effects (less competition for a shared food source, so a different species increases)
- For the extended reforestation/conservation question, cover both named topics separately, each with detail on process and outcome
What is the best definition of biodiversity?
Human impact questions want the specific mechanism traced through the food web or ecosystem, covering every named topic in the question.
Practise human impacts on biodiversity“Describe the full route of blood flow through the heart and lungs, and explain why artery walls differ from vein walls”
Both sittings we have full data for test the circulatory system directly, either as a full extended-response blood-flow question or as a structural artery/vein comparison.
1×asked“Blood from the body enters the heart through the vena cava. Describe how this blood flows through the heart and lungs to leave the heart through the aorta. Include references to the chambers of the heart and the relevant valves in your answer.”
“Blood from the body enters the heart through the vena cava. Describe how this blood flows through the heart and lungs to leave the heart through the aorta. Include references to the chambers of the heart and the relevant valves in your answer.”
What it’s really asking
It wants the full continuous path of blood from the vena cava through the right side of the heart, to the lungs, back through the left side of the heart, and out through the aorta, with named chambers and valves at each stage.
The full worked answer — June 2019
Blood flows from the vena cava into the right atrium, then through a valve into the right ventricle.
From the right ventricle, blood is pumped through the pulmonary artery, through a valve, to the lungs, where it picks up oxygen and releases carbon dioxide.
Oxygenated blood then returns from the lungs to the heart through the pulmonary vein, entering the left atrium, and then passes through a valve into the left ventricle.
Finally, blood is pumped from the left ventricle through a valve into the aorta, to be carried around the body. The valves throughout the heart prevent blood from flowing backwards at each stage.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise the heart and circulationWhat the mark scheme rewarded
- Blood flows from vena cava into the right atrium, into the right ventricle, through a valve, and is pumped into the pulmonary artery, through a valve, to the lungs
- From the lungs back to the heart through the pulmonary vein, into the left atrium, into the left ventricle, through a valve, pumped into the aorta, through a valve
- Valves prevent backflow
- Level 3 (5 to 6 marks) requires a correct reference to blood flow through the heart from right to left, travelling through the lungs, including valves, correctly linked to the pulmonary artery and pulmonary vein
- The heart is a double pump, with the right side pumping deoxygenated blood to the lungs and the left side pumping oxygenated blood to the rest of the body, which is why the left ventricle has a thicker muscular wall than the right
- Valves in the heart snap shut when blood tries to flow backwards, producing the 'lub-dub' sound heard through a stethoscope
Traps examiners saw
- Naming the pulmonary artery as carrying oxygenated blood or the pulmonary vein as carrying deoxygenated blood, this is reversed from the usual body artery/vein pattern and is a very common error
- Missing out named valves at each transition, since 'blood goes to the ventricle' without stating it passes through a valve loses that specific credited point
Full-mark self-check 0 of 4
1×asked“Explain one difference between the artery wall and the vein wall shown.”
“Explain one difference between the artery wall and the vein wall shown.”
What it’s really asking
It wants the specific difference (artery wall is thicker/more muscular) linked to the reason (arteries carry blood at higher pressure than veins).
What the sources actually showed — June 2022
A cross-section microscope image showing an artery and a vein side by side, with the artery wall and vein wall separately labelled.
The full worked answer — June 2022
The artery wall is thicker and more muscular than the vein wall.
This is because blood in arteries is at a much higher pressure than blood in veins, and the thicker, more muscular wall helps the artery withstand this pressure and prevent it from bursting.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise the heart and circulationWhat the mark scheme rewarded
- Artery has a thicker/more muscular wall
- Because of the (blood) pressure (higher in artery than vein) (accept prevent the artery bursting/maintain blood pressure)
- Veins also contain valves, which arteries do not have, since blood in veins is at low pressure and needs help to prevent it flowing backwards, especially against gravity
- Artery walls contain more elastic and muscle tissue than vein walls, allowing them to stretch and recoil with each surge of blood pumped from the heart
Traps examiners saw
- Stating only 'artery walls are thicker' without linking this to the pressure difference, the structural observation alone does not earn both marks
Full-mark self-check 0 of 2
The method for every Q8/Q3 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Describing the FULL route through both sides of the heart in the correct order, including named valves and vessels
- Linking artery wall thickness to blood pressure specifically, not just 'arteries are thicker'
The steps
- For the full blood flow question, trace one continuous path: vena cava, right atrium, right ventricle, valve, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, valve, aorta
- Name the valves at each transition point between chambers, this is explicitly credited
- For structure questions, always link wall thickness to blood pressure difference, and remember valves are specific to veins (preventing backflow at low pressure)
How many chambers does the human heart have?
Heart and circulation questions want the FULL route through both sides of the heart with named valves, not a shortened version.
Practise the heart and circulation“State why rose plants near a polluting factory are not infected with blackspot fungus”
Both sittings we have full data for use blackspot fungus on rose leaves in the context of air pollution, always asking why the disease does or does not appear under polluted conditions.
2×asked“State why rose plants growing near this factory are not infected with blackspot fungus.”
“State why rose plants growing near this factory are not infected with blackspot fungus.”
What it’s really asking
It wants the specific reason blackspot fungus is absent near a polluting factory, that it cannot grow where sulfur dioxide levels are high.
What the sources actually showed — June 2022
A photograph of a diseased rose plant's leaves, showing dark blackspot patches spreading across several leaflets.
The full worked answer — June 2022
Blackspot fungus will not grow where areas have high sulfur dioxide (air pollution) levels, such as near this factory.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise plant diseases and defencesWhat the sources actually showed — June 2023
A photograph of rose leaves infected with blackspot fungus, showing dark spotted patches on several leaflets.
The full worked answer — June 2023
The blackspot fungus will not grow where areas have high sulfur dioxide levels, and this factory releases sulfur dioxide into the air, which is why the roses growing there are free of the fungus.
Could you have written this? Every fact in this answer is drilled in our quizzes — the writing is the easy part once the evidence is automatic.
Practise plant diseases and defencesWhat the mark scheme rewarded
- Blackspot fungus will not grow where areas have high sulfur dioxide (accept sulfur alone)
- Blackspot fungus, alongside lichen, is used as a biological indicator of air quality, since it can only survive and spread where sulfur dioxide levels are low
- Sulfur dioxide is released by burning fossil fuels such as coal, which is why factories located near sensitive plant species can be identified by an absence of pollution-sensitive fungi like blackspot
Traps examiners saw
- Describing what blackspot fungus does to a healthy plant (dark spots, leaf damage) instead of explaining WHY it is absent specifically near this polluting factory
Full-mark self-check 0 of 1
The method for every Q1/Q1 — same every sittingMark bands, steps, timing
What this question type rewards
The topic changes by sitting — the mark scheme never does. Learn this once, then open your question above for that sitting’s sources and a full worked answer.
- Linking sulfur dioxide (or general air pollution) specifically to blackspot fungus being unable to grow, rather than a vague 'pollution kills it'
The steps
- Name sulfur dioxide specifically as the pollutant blackspot fungus cannot tolerate
- State the fungus will not grow/cannot survive in these conditions, rather than describing symptoms of the disease itself
What type of pathogen causes rose black spot disease?
Blackspot fungus questions always want sulfur dioxide named as the specific reason it cannot survive near polluting factories.
Practise plant diseases and defencesThe topics that keep coming up
Across the 3 sittings we have full papers for, these are the topics with the most exam appearances and marks at stake in Biology Paper 2.
Not the primary focus in the 3 sittings we have full papers for
Homeostasis introduction as a standalone definition question · Fertility treatment (IVF) as a standalone extended-response topic · Decomposition rate practicals as a standalone question separate from the nitrogen/carbon cycles · Competition and adaptations as a standalone topic separate from food web questions
These topics have not been the main focus of a Paper 2 question in the three sittings we analysed directly, but the specification still covers them, so do not skip them.
Before you revise
Are these real mark-scheme answers?
The sources and diagrams are described in our own words, not reproduced, and the worked answers are written entirely by us, aimed at what the real Edexcel mark schemes for June 2019, June 2022 and June 2023 actually rewarded. They are not copied from Edexcel's own exemplar answers, since that would breach copyright, but every mark point traces back to a real, published mark scheme. PrepWise is independent of Pearson and Edexcel and not endorsed by them.
Why do some sittings only have partial worked answers for a topic?
Not every topic appears in every sitting, and where a topic only appears in one or two of the three sittings, we only build worked answers from the real questions that were actually asked. We never invent a question or a source to fill a gap.
Will the exact same questions come up again this year?
Sometimes the underlying topic returns closely (water regulation, the carbon cycle, and gas exchange have appeared in all three sittings we have), but the exact numbers, diagrams and scenarios change every time. Use this page to learn which TOPICS keep returning and build a strong evidence bank for each one, rather than memorising one year's exact answer.
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