Edexcel iGCSE Biology 4BI1 - Paper 2B - Food production- Exam Style Questions- New Syllabus

Question

The photograph shows a fish called tilapia. This type of fish is often grown in fish farms.

(a) Tilapia are a good source of nutrients for humans.

The table shows the percentage of the daily requirements for humans of three nutrients provided by a portion of tilapia.

Nutrient group	Percentage of daily requirement provided by a portion of tilapia
lipids	16
protein	38
carbohydrate	16

(i) Use the table to determine the ratio of lipid to protein to carbohydrate.

Give your answer in the form $1 : n : 1$

(ii) Describe how to test a sample of tilapia to show the presence of lipid.

(iii) State one function of protein in the human body.

(b) Scientists have produced genetically modified (GM) tilapia that grow faster.

Scientists investigate the growth of these GM tilapia compared with non-genetically modified (non-GM) tilapia.

This is the scientists’ method.

set up two equally sized tanks containing water
put non-GM tilapia into one tank
put an equal mass of GM tilapia into the second tank
feed the fish in each tank the same mass of protein pellets

The mass of each type of fish was measured at the start of the investigation and after seven months.

A measure called the feed conversion index was also calculated for each type of fish.

The table shows the scientists’ results.

Type of fish	Total starting mass of fish in g	Total mass of fish after seven months in g	Feed conversion index
non-GM	1250	2830	1.9
GM	1250	3750	1.2

(i) The mean rate of increase in mass of the non-GM tilapia during the seven months is $226 \, \text{g}$ per month.

Calculate the mean rate of increase in mass, in g per month, of the GM tilapia.

Give your answer to three significant figures.

(ii) The feed conversion index is a measure of the mass of protein pellets used compared with the increase in mass of tilapia.

It is calculated using this formula.

$\text{feed conversion index} = \frac{\text{total mass of protein pellets used}}{\text{increase in mass of tilapia}}$

Use the information in the table to calculate the mass of protein pellets given to the non-GM tilapia.

(iii) Suggest why the GM tilapia have a lower feed conversion index than the non-GM tilapia.

(iv) Both groups of fish were fed the same mass of pellets and placed into the same sized tanks of water.

Give one other abiotic factor that the scientists should keep constant.

(v) The scientists conclude that farming GM tilapia is better for the environment than farming non-GM tilapia. This is because the GM tilapia would result in less nitrate in the water and cause less spread of disease. Evaluate this conclusion.

Use the information in the table and your own knowledge in your answer.

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 2(c): Biological molecules — parts (a)(ii), (a)(iii)
• 2(e): Nutrition — part (a)(i), (a)(iii)
• 5(a): Food production (Fish farming) — parts (b)(i), (b)(ii), (b)(iii), (b)(iv), (b)(v)
• 5(c): Genetic modification (genetic engineering) — parts (b)(i), (b)(iii), (b)(v)
• 4(a): The organism in the environment (Abiotic factors) — part (b)(iv)

▶️ Answer/Explanation

Solution

(a)(i) $1 : 2.4 : 1$
Accept $1: 2.375: 1$

(a)(ii) A description that makes reference to the following points:
• ethanol / alcohol and add water (1)
• goes white / cloudy / white emulsion forms / milky / eq (1)
OR
• add Sudan III (1)
• red colour (in top layer) (1)
Accept alternative method: rub on paper / eq (1); paper goes transparent / clear / eq (1)

(a)(iii) • growth / repair / enzymes / build muscle / antibodies / eq (1)

(b)(i) • $357 \, \text{g per month}$ (2)
Correct answer gains both marks.
Accept one mark for:
$2500$ (increase) or division by $7$ or $(3750-1250)$ or $357.14…$

(b)(ii) • $3002 / 3000 \, \text{g}$ (1)

(b)(iii) An answer that makes reference to two of the following points (1 mark each):
• (GM fish) grow more / bigger / faster / eq
• produce less faeces / can digest more efficiently / absorb more / eq
• less respiration / lower metabolic rate / eq
• move less / slower swimming / eq
• eat more food / less food wasted / eq

(b)(iv) • temperature / light (intensity) / oxygen / salinity / pH / eq (1)

(b)(v) An evaluation that makes reference to the following points (up to 5 marks):
1. GM fish grow bigger/faster/harvest sooner / eq (1)
2. less food wasted / more food eaten / eq (1)
3. less faeces / urea / excretion / ammonia / eq (1)
4. less decomposition / fewer decomposers / eq (1)
5. less nitrification / fewer nitrifying bacteria / eq (1)
6. less eutrophication / algal growth / plant growth / eq (1)
7. less oxygen loss / more oxygen in water / eq (1)
8. due to less (bacterial) respiration / (more oxygen for) respiration of animals / eq (1)
9. no information about disease spread / pathogen spread / eq (1)
10. GM fish are (genetically) similar so may be more likely to catch/spread disease / eq (1)
11. not repeated / need more experiments / no idea of sample size / eq (1)
12. (GM) fish that escape may harm food chains / outcompete wild fish / may breed with wild fish / eq (1)
13. did not measure nitrates / eq (1)

Question

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Offshore or freshwater fish farming

Fish farming in fresh water and in the sea offers the potential to increase the amount of fish harvested whilst protecting wild fish stocks. Offshore or fish farming at sea has less risk of serious injury or death to people than catching fish by deep sea fishing.

Some scientists predict that smart fish farming at sea could increase ocean fish production by an estimated 21 million tonnes from the 2020 value to 44 million tonnes by 2050. Other estimates suggest that fish farming at sea, using an area the size of Lake Michigan, might produce the same amount of seafood as all of the world’s wild-caught fisheries.

Fish farming at sea is done anywhere from three to 200 miles away from the coast. The fish produced are often Atlantic salmon, seabass and cobia. The aim is to reduce the environmental impact of fish farming near the coast by moving them further away from sensitive shorelines. This limits the impact of disease, pollution and pests such as sea lice. Further out to sea, and at deeper depths, the water movement is often faster.

Critics of fish farming at sea claim that it will be more difficult to monitor and regulate any environmental impact and that pollution, disease and pests would still impact the surrounding waters. A major risk of farming at sea is the exposure to high winds and water speeds, increasing the risk of all the fish escaping. In 1997, 300 000 farmed Atlantic salmon escaped into the Pacific Ocean. Wild fish are attracted to the farms by the scent of fish food. These wild fish are at risk of being hit by ships travelling to and from the large fish farms.

In contrast, other scientists support the development of fish farming in fresh water. Freshwater fish farms have increased in numbers steadily in the past 30 years. Asia is the main part of the world where this has happened. It is relatively cheap and easy to grow freshwater fish in small ponds. Fish farming provides incomes for many family farms, workers and small businesses, as well as jobs.

The main species produced by freshwater farming are carp, tilapia and catfish. These fish are herbivores or omnivores. In the farms they are fed small amounts of fish to speed up growth, but their main diet is the by-products of crops like rice, groundnut and soy. Farmed freshwater fish are an affordable food for millions of low- and middle-income consumers.

(a) Suggest why deep sea fishing has a risk of serious injury or death to people. (lines 2 to 3)

(b) Give three reasons why the scientists’ prediction of an increase in ocean fish production to 44 million tonnes by 2050 is only an estimate. (lines 4 to 6)

(c) Explain how fish farms cause pollution. (lines 12 to 16)

(d) Fish farmers use methods to control disease in their fish farms.

(i) Describe the methods a fish farmer could use to reduce the incidence of disease in a fish farm.
(ii) Explain how these methods may affect the local ecosystem.

(e) Explain why locating the fish farms further out to sea may help reduce the effects on the local ecosystem. (lines 12 to 16)

(f) Suggest why fish farming further out at sea will be more difficult to monitor and regulate. (lines 14 to 16)

(g) Give a reason why farming fish that are herbivores is an advantage for the fish farmer. (lines 27 and 28)

(h) Explain why small, local freshwater fish farms would have less impact on global warming than large fish farms at sea.

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 4(d): Human influences on the environment — parts (c), (e)
• 5(a): Food production (Fish farming) — parts (a), (b), (d)(i), (d)(ii), (f), (g), (h)
• 5(b): Selective breeding — part (d)(i)
• 5(c): Genetic modification — part (d)(i)

▶️ Answer/Explanation

Solution

(a) • drowning / being washed overboard / sinking / storms / (bad) weather / attacked / killed by sharks by predators / eq (1)

(b) An explanation that makes reference to three of the following points: (3)
1. only based on forecasts / model / not happened yet / can’t predict future / 30 years is a long way off / not guaranteed / eq (1)
2. other (scientists) have different view / only an opinion / government policy may change / eq (1)
3. amount of sea farms may change / may not work / unproven / untested / eq (1)
4. peoples’ tastes may changes / diet / choices / demand for fish may change / eq (1)
5. effect of climate change / sea temperature rising / levels rising / global warming /eq (1)
6. effect of pollution / eq (1)

(c) An explanation that makes reference to three of the following points: (3)
1. (fish) faeces / waste / uneaten food /eq (1)
2. nitrate / phosphate levels increase / eq (1)
3. leads to algal growth / eutrophication / (eq)
4. less oxygen (for respiration)/ oxygen used (by bacteria) / eq (1)
5. chemicals / hormones /eq (1)
6. bacteria / decomposers / eq (1)

(d)(i) A description that makes reference to two of the following points: (2)
1. pesticide / insecticide / fungicide / eq (1)
2. antibiotics / vaccinate fish / eq (1)
3. selective breeding / GM fish / eq (1)
4. separating / isolating diseased fish / removing sick / dead fish / eq (1)
5. low stocking density /eq (1)

(d)(ii) An explanation that makes reference to two of the following points: (2)
1. pesticide / insecticide / fungicide/ antibiotic / kill other organisms / disrupt food chain /eq (1)
2. (pesticide / insecticide / fungicide / antibiotics ) can (bio)accumulate / eq (1)
3. (antibiotics) lead to antibiotic resistance / eq (1)
4. selective bred / GM organisms may escape and interbreed / eq (1)

(e) An explanation that makes reference to two of the following points: (2)
1. deep water / greater volume / eq (1)
2. (so) dilution / reduces concentration / eq (1)
3. fast water flowing / eq (1)
4. (so) dispersed / carried away / eq (1)

(f) An answer that includes: (1)
• further from shore / further from land / isolated / longer distance to travel / no population nearby / need to use boat to reach / take a long time to get there / eq (1)

(g) An answer that includes one of: (1)
• is cheaper / use cheaper food (readily available) / surplus food / crop waste /eq (1)
• more efficient energy transfer / eq (1)
• will not eat each other / other fish / eq(1)

(h) An explanation that makes reference to two of the following points: (2)
• less fuel / less transport of equipment /supplies / workers / less food miles / eq (1)
• less energy used / less electricity / less machinery (in running / building) / eq (1)
• less carbon dioxide released (from burning the fossil fuel) / eq (1)

Total = 17 marks

Question

(a) Using the recommended amount of fertiliser on a crop increases crop yield. Some farmers think that adding extra fertiliser will give an even greater crop yield.

(i) Give a reason why adding extra fertiliser does not result in an even greater crop yield.

(ii) Some farmers apply more nitrogen fertiliser and more water to their fields than are needed.

Explain the biological consequences of applying more nitrogen fertiliser and more water than needed.

(b) The atmosphere can be polluted by gases such as carbon monoxide released from industry.

Describe the effects of carbon monoxide on the human body.

(c) Which of these is not a greenhouse gas?

A. carbon dioxide
B. methane
C. nitrogen
D. nitrous oxide

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 5(a): Food production – Crop plants – effects of fertiliser on yield (parts a(i), a(ii))
• 4(d): Human influences on the environment – eutrophication (part a(ii))
• 4(d): Human influences on the environment – air pollution (part b)
• 2(g): Gas exchange – effects of carbon monoxide on gas transport (part b)
• 4(d): Human influences on the environment – greenhouse gases (part c)

▶️ Answer/Explanation

Solution

(a)(i) Excess fertiliser is not absorbed by the plants / some is washed away.

Explanation: Plants can only absorb a certain amount of nutrients from the soil. When fertiliser is applied beyond the recommended amount, the plant roots become saturated and cannot take up any more minerals. The excess fertiliser remains in the soil where it can be easily washed away by rainwater through a process called leaching. This means the extra fertiliser doesn’t contribute to plant growth and is essentially wasted.

(a)(ii) Applying excess nitrogen fertiliser and water leads to waterlogging of soil, leaching, eutrophication, oxygen depletion in water bodies, and death of aquatic organisms.

Explanation: When farmers apply more water than needed, the soil becomes waterlogged. Water fills the air spaces in the soil, creating anaerobic conditions where oxygen is lacking. Plant root cells need oxygen to perform active transport for mineral uptake, so they cannot absorb nutrients effectively in waterlogged conditions.

Excess nitrogen fertiliser gets washed away (leached) into nearby rivers and lakes through runoff. This extra nitrogen acts as a nutrient source for algae, causing rapid algal growth known as algal bloom. The algae form a thick layer on the water surface, blocking sunlight from reaching underwater plants. Without sunlight, these plants cannot photosynthesize and eventually die.

The dead plants and algae are decomposed by bacteria, which respire and consume large amounts of oxygen in the water. This leads to oxygen depletion (anoxic conditions), causing fish and other aquatic organisms to suffocate and die. This entire process of nutrient overload leading to ecosystem collapse is called eutrophication.

(b) Carbon monoxide combines with haemoglobin to form carboxyhaemoglobin, preventing oxygen transport in the blood.

Explanation: When inhaled, carbon monoxide binds to haemoglobin in red blood cells with a much greater affinity than oxygen, forming carboxyhaemoglobin. This prevents haemoglobin from carrying oxygen to body tissues. As a result, cells throughout the body receive less oxygen, leading to reduced respiration and energy production. In severe cases, this oxygen deprivation can cause headaches, dizziness, unconsciousness, and even death. The body may also resort to anaerobic respiration, producing lactic acid which can lead to muscle fatigue and pain.

(c) C (nitrogen)

Explanation: While nitrogen (N₂) makes up about 78% of the atmosphere, it is not considered a greenhouse gas because it is largely transparent to infrared radiation and does not significantly contribute to the greenhouse effect. In contrast, carbon dioxide (A), methane (B), and nitrous oxide (D) are all potent greenhouse gases that trap heat in the atmosphere and contribute to global warming.

Question

Scientists use a calorimeter to compare the energy content of different types of grain.

This is the scientists’ method:

put 20 cm³ of water into the calorimeter
measure the initial temperature of the water
place 1 g of a grain type in the small dish
place the small dish in the calorimeter
light the grain in the small dish
allow the grain to completely burn
measure the final temperature of the water

They repeat this method with different types of grain.

(a) Explain how the scientists could use these measurements to calculate the energy released by 1 g of the grain.

(b) State how the scientists can make sure that their results are reliable.

(c) (i) This calorimeter has a twisted waste gas pipe passing through the water. Explain how the twisted waste gas pipe improves the accuracy of the scientists’ results compared with a straight pipe.

(ii) This calorimeter burns the grain in oxygen. Give a reason why this improves the accuracy of the scientists’ results.

(d) The scientists also collected data on the protein, fat, carbohydrate and fibre content of the grains.

The table shows some of the scientists’ results.

(i) Calculate the mass of protein in 65 g of rice.

(ii) A long-distance athlete wants to choose a grain to add to their diet. Comment on the suitability of each grain type for the diet of a long-distance athlete.

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 5(a): Food production — investigating energy content in food
• 2(e): Nutrition — balanced diet, energy requirements, and food composition
• 2(e): Humans — energy requirements, diet components, and nutritional analysis
• Appendix 6: Suggested practical investigations — investigating energy content in a food sample (2.33B)

▶️ Answer/Explanation

Solution

(a) The scientists can calculate the energy released by 1 g of grain using the formula: Energy = mass of water × specific heat capacity of water × temperature change.

Explanation: First, they need to calculate the temperature change (ΔT) by subtracting the initial temperature from the final temperature. Then, they multiply this temperature change by the mass of water (20 g, since 20 cm³ of water has a mass of 20 g) and by the specific heat capacity of water (4.2 J/g°C). This gives the energy in joules. To find the energy per gram of grain, they would divide this value by 1 (since they used 1 g of grain). The formula can be written as: E = m × c × ΔT, where m = 20 g, c = 4.2 J/g°C, and ΔT = final temperature – initial temperature.

(b) Repeat the experiment multiple times and calculate the mean.

Explanation: To ensure reliability, scientists should repeat the experiment several times for each type of grain. By calculating the average (mean) of these repeated measurements, they can reduce the effect of random errors and obtain a more reliable result that better represents the true value.

(c)(i) The twisted pipe has a larger surface area, allowing more heat to be transferred to the water.

Explanation: A twisted waste gas pipe increases the surface area that comes into contact with the water compared to a straight pipe. This enhanced surface area allows for more efficient heat transfer from the hot waste gases to the water, ensuring that more of the energy released from burning the grain is captured and measured. This results in a more accurate measurement of the energy content.

(c)(ii) Oxygen ensures complete combustion of the grain.

Explanation: Burning the grain in pure oxygen rather than air ensures that the grain undergoes complete combustion. In air, which contains only about 21% oxygen, incomplete combustion might occur, leading to soot formation and the release of less energy. Pure oxygen guarantees that all the combustible material in the grain is fully oxidized, releasing the maximum possible amount of energy, which provides a more accurate measurement of the grain’s energy content.

(d)(i) Mass = 4.55 g

Explanation: According to the table, rice contains 7 g of protein per 100 g. To find the mass of protein in 65 g of rice, we set up a proportion: (7 g protein / 100 g rice) = (x g protein / 65 g rice). Solving for x: x = (7 × 65) / 100 = 455 / 100 = 4.55 g. Therefore, 65 g of rice contains 4.55 g of protein.

(d)(ii)

Oats: Oats are highly suitable because they have high carbohydrate (62 g/100 g) and fat (7 g/100 g) content, providing sustained energy release for endurance activities. They also contain a moderate amount of protein (13 g/100 g) for muscle repair. However, the relatively high fat content might be a concern if consumed in large quantities over time.

Rye: Rye has moderate carbohydrates (60 g/100 g) but low fat (2 g/100 g) and protein (8 g/100 g), making it less ideal as a primary energy source. Its high fiber content (14 g/100 g) is beneficial for digestive health but might cause gastrointestinal discomfort during intense exercise if consumed in large amounts shortly before running.

Rice: Rice is excellent for quick energy due to its very high carbohydrate content (74 g/100 g) and low fiber (3 g/100 g), which allows for easy digestion. However, it has low protein (7 g/100 g) and fat (2.5 g/100 g), so it should be complemented with other protein sources for muscle recovery.

Wheat: Wheat has the highest protein content (28 g/100 g), which is beneficial for muscle repair and growth. However, its relatively low carbohydrate content (32 g/100 g) makes it less optimal as a primary energy source for endurance activities compared to oats or rice. The high fiber content (14 g/100 g) is good for general health but might not be ideal immediately before exercise.

Overall: For a long-distance athlete who needs sustained energy, oats would be the best choice due to their balanced macronutrient profile with high carbohydrates and moderate fat and protein. Rice could be good for quick energy before a race. Wheat is valuable for muscle repair but lower in energy, and rye is the least suitable due to its lower energy density.

Question

The following passage contains information about using micropropagation to produce plants.

Complete the passage by writing a suitable word in each blank space. (6)

Micropropagation uses small fragments of plants which are regrown into whole plants. These fragments of plants are known as __.

The surface of each fragment is sterilised to prevent growth of __. The fragments are placed in a growth medium. The growth medium contains agar and a source of energy such as __.

This method is able to produce large quantities of genetically identical plants called __.

One advantage is that micropropagation is quicker than __ reproduction, which involves flower and seed production. Another advantage of micropropagation is that plants can be produced __ the year.

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 5(d): Cloning — micropropagation, explants, cloning
• 3(a): Reproduction — sexual vs asexual reproduction
• 5(a): Food production — growth media, sterilisation

▶️ Answer/Explanation

Solution

Completed passage:

Micropropagation uses small fragments of plants which are regrown into whole plants. These fragments of plants are known as explants.

The surface of each fragment is sterilised to prevent growth of microorganisms. The fragments are placed in a growth medium. The growth medium contains agar and a source of energy such as sugar.

This method is able to produce large quantities of genetically identical plants called clones.

One advantage is that micropropagation is quicker than sexual reproduction, which involves flower and seed production. Another advantage of micropropagation is that plants can be produced throughout the year.

Detailed Explanation:

Explants are small pieces of plant tissue (such as shoot tips, leaves, or stem segments) that are used in micropropagation. These explants are sterilized to eliminate any microorganisms (like bacteria or fungi) that could contaminate the culture and hinder plant growth. The growth medium contains agar to provide a solid surface and sugar (usually sucrose) as an energy source since the explants may not be able to photosynthesize effectively initially.

Micropropagation produces clones, which are genetically identical plants. This ensures uniformity in characteristics like growth rate, flower color, or fruit quality. Compared to sexual reproduction (which involves pollination, seed formation, and germination), micropropagation is faster because it bypasses these stages and allows for rapid multiplication. Additionally, micropropagation can be done throughout the year under controlled laboratory conditions, independent of seasonal changes that affect traditional planting.

Question

Measles is a disease caused by a virus. The graph shows the number of cases of measles each year and the percentage of five year-olds vaccinated between 1950 and 2016 in the United Kingdom.

(a) Determine the difference in the percentage change in the number of cases of measles between 1950 and 1965 and the percentage change in the number of cases of measles between 1968 and 1983.

(b) Explain the relationship between the number of cases of measles and the percentage of five year-olds vaccinated. Use information from the graph in your answer.

(c) Some children are receiving treatments that reduce the activity of their immune system. Explain why vaccinations are not used on these children.

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 1(b): Variety of living organisms — part (a) (knowing measles is viral)
• 2(h): Transport — part (c) (immune response, antibodies)
• 5(a): Use of biological resources — part (b) (vaccination as a biological control method)
• 4(d): Human influences on the environment — part (b) (public health, vaccination programmes)

▶️ Answer/Explanation

Solution

(a) Difference = approximately 105% (range: 94-106%)

Explanation: To calculate this difference, we need to find the percentage change for each time period separately and then find the difference between them.

For 1950-1965: Cases increased from approximately 400-420 to 510-520. Using the midpoint values (410 to 515):

Percentage change = $\frac{515 – 410}{410} \times 100 = \frac{105}{410} \times 100 ≈ 25.6\%$

For 1968-1983: Cases decreased from approximately 480-490 to 120-130. Using the midpoint values (485 to 125):

Percentage change = $\frac{125 – 485}{485} \times 100 = \frac{-360}{485} \times 100 ≈ -74.2\%$

Difference = |25.6 – (-74.2)| = 99.8% (approximately 100%)

The exact answer may vary slightly depending on the precise values read from the graph, but should fall within the range of 94-106%.

(b) The relationship shows that as vaccination rates increase, measles cases decrease significantly.

Explanation: The graph demonstrates an inverse relationship between vaccination rates and measles cases. Before widespread vaccination (pre-1968), cases were high and fluctuated significantly. After the introduction of vaccination, cases began to decline steadily as vaccination rates increased.

For example, in the early 1970s when vaccination rates were around 50-60%, cases dropped to about 100-200 thousand. By the 1990s, when vaccination rates reached 80-90%, cases fell dramatically to very low levels (less than 20 thousand). This shows that vaccination provides herd immunity, reducing the virus’s ability to spread through the population.

The relationship is not perfectly linear because other factors like vaccination campaigns, public awareness, and natural immunity from previous infections also play a role. However, the overall trend clearly shows that higher vaccination coverage leads to fewer measles cases.

(c) Vaccinations are not used on immunocompromised children because they may not develop proper immunity and could develop the disease.

Explanation: Children with compromised immune systems (due to treatments like chemotherapy or immunosuppressive drugs) have reduced ability to produce antibodies and memory cells in response to vaccines. Vaccines contain weakened or inactivated pathogens that stimulate the immune system to create protection.

In immunocompromised children, their weakened immune systems may not be able to mount an effective response to the vaccine, leaving them unprotected. Even more concerning, there’s a risk that the weakened pathogen in the vaccine could cause the actual disease in these vulnerable children.

Instead of vaccination, these children rely on herd immunity – the protection provided when enough people in the community are vaccinated to prevent the disease from spreading. This is why high vaccination rates in the general population are so important, as they protect those who cannot be vaccinated themselves.

Question

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

When the Oceans Glow

In some areas of the world the oceans around the coast sometimes glow with a blue light. The photograph shows an area of coast that is glowing. This blue light is produced by the presence of thousands of microscopic, living organisms called dinoflagellates. These dinoflagellates are protocysts. The production of light by living organisms is called bioluminescence, a process that has evolved many times in different species of organism.

To generate light, dinoflagellates use special proteins and the ATP produced within their cells. Many species of dinoflagellate contain chlorophyll and are able to photosynthesize. The appearance of glowing dinoflagellates in the sea used to be a rare event but this now occurs much more frequently. Many of the events occur in the sea around river estuaries and scientists think that intensive farming and deforestation could be to blame. Due to overpopulation of dinoflagellates in these areas, other species of animal are often harmed. After a series of glowing events, large numbers of dinoflagellates die causing oxygen levels in the water to decrease.

People have often wondered why dinoflagellates glow. They only glow in areas where the water moves around, such as when waves hit a beach. Scientists now think that the production of light is a type of warning to stop predators eating the dinoflagellates. If an animal eats dinoflagellates, the dinoflagellates in the area glow making the animal obvious to its own predators. To test this, scientists placed dinoflagellates into a tank along with 15 copepods, which are predators of dinoflagellates. When the dinoflagellates glowed, the copepods ate 1200 dinoflagellates in two hours. When the dinoflagellates did not glow, the copepods ate 2100 dinoflagellates in two hours.

Some scientists think that we could make use of the dinoflagellates to provide sustainable street lighting. Tanks of dinoflagellates could be placed on top of lamp posts. The dinoflagellates would photosynthesize during the day when it is light. A stirrer powered by a small battery would then move them at night so that they would glow. These sustainable lamps could be carbon neutral and help to reduce pollution.

(a) Which of these processes produces ATP? (line 6)

A. active transport
B. diffusion
C. respiration
D. transpiration

(b) (i) Explain why intensive farming and deforestation would cause an increase in populations of dinoflagellates. (lines 9 to 11)

(ii) Explain why oxygen levels decrease after a series of glowing events. (lines 10 to 13)

(c) Which type of bacteria converts ammonia into nitrates?

A. decomposer
B. denitrifying
C. nitrifying
D. nitrogen fixing

(d) (i) Each of the 15 copepods ate glowing dinoflagellates at a mean rate of 40 dinoflagellates per hour. Calculate the mean rate at which each copepod ate dinoflagellates that were not glowing. (lines 18 to 21)

(ii) Explain how natural selection could have resulted in the evolution of dinoflagellates that glow. (lines 15 to 18)

(e) Explain why using dinoflagellates for street lighting would help to reduce pollution. (lines 22 to 26)

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 1(b): Variety of living organisms — identification of dinoflagellates as protocysts
• 2(f): Respiration — part (a) ATP production
• 2(e): Nutrition (Photosynthesis) — reference to chlorophyll and photosynthesis in dinoflagellates
• 4(d): Human influences on the environment — parts (b)(i), (e) pollution, eutrophication, deforestation
• 4(c): Cycles within ecosystems (Nitrogen cycle) — part (c) role of bacteria
• 3(b): Inheritance and evolution — part (d)(ii) natural selection
• 2(e): Nutrition (Diet and energy) — part (d)(i) calculation of feeding rate
• 5(a): Use of biological resources (Food production) — part (e) sustainable use of organisms

▶️ Answer/Explanation

Solution

(a) C (respiration)

Explanation: Respiration is the metabolic process that breaks down glucose to release energy, which is stored in ATP molecules. Active transport uses ATP but does not produce it. Diffusion is a passive process and does not require or produce ATP. Transpiration is the loss of water vapor from plants and is not directly involved in ATP production.

(b)(i)

Explanation: Intensive farming often involves the heavy use of fertilizers. Deforestation removes trees whose roots help bind the soil. The combination of these factors leads to soil erosion. When it rains, eroded soil and excess fertilizers (rich in minerals like nitrates and phosphates) are washed into rivers and eventually into estuaries and the sea. These minerals act as nutrients for dinoflagellates, allowing their populations to grow rapidly, a process known as eutrophication.

(b)(ii)

Explanation: After the glowing events, large numbers of dinoflagellates die. Their bodies are decomposed by bacteria and other microorganisms. These decomposers respire as they break down the organic matter, a process that consumes oxygen. The large algal bloom may also block light, reducing photosynthesis and oxygen production by other organisms. The high rate of oxygen consumption by decomposers leads to a decrease in dissolved oxygen levels.

(c) C (nitrifying)

Explanation: Nitrifying bacteria are specifically responsible for converting ammonia into nitrites and then into nitrates in the nitrogen cycle. Decomposer bacteria break down organic matter into ammonia. Denitrifying bacteria convert nitrates back into nitrogen gas. Nitrogen-fixing bacteria convert atmospheric nitrogen gas into ammonia.

(d)(i) 70 dinoflagellates per hour

Explanation: The total number of non-glowing dinoflagellates eaten in 2 hours was 2100. The total eaten per hour is $ 2100 \div 2 = 1050 $ dinoflagellates per hour. This is the rate for all 15 copepods. The mean rate per copepod is $ 1050 \div 15 = 70 $ dinoflagellates per hour per copepod.

(d)(ii)

Explanation: A random mutation gave some dinoflagellates the allele to glow. This created variation. When predators were present, dinoflagellates that glowed were less likely to be eaten (as the glow attracted the predators’ own predators). These dinoflagellates had a higher survival rate and were more likely to reproduce, passing the advantageous allele for glowing to their offspring. Over many generations, the frequency of the glowing allele increased in the population, leading to the evolution of this trait.

(e)

Explanation: It would reduce reliance on electricity generated from burning fossil fuels. The dinoflagellates photosynthesize during the day, taking in carbon dioxide ($CO_2$) from the atmosphere. At night, they produce light through bioluminescence without burning fuels. Therefore, this method produces no direct air pollutants and contributes less to the greenhouse effect, making it a more sustainable and carbon-neutral alternative.

Question

Fish farming is often used to produce protein rich food.

(a) Selective breeding is often used to produce fish that grow rapidly and do not waste much food.

Explain how selective breeding can be used to produce fish that grow rapidly.

(b) Fish farming systems can often release ammonia into the water. The ammonia is converted into nitrates.

Describe how ammonia is converted into nitrates.

(c) Multi-trophic level aquaculture is a method of fish farming that has been developed to reduce environmental pollution and increase profits.

The diagram shows a multi-trophic level aquaculture system.

Explain how the multi-trophic level aquaculture system reduces environmental pollution, and increases the profits of fish farming.

Use information from the diagram and your own knowledge to support your answer.

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 5(a): Food production — part (a), (c) (fish farming context)
• 5(b): Selective breeding — part (a) (selective breeding in animals)
• 4(c): Cycles within ecosystems — part (b) (nitrogen cycle processes)
• 4(d): Human influences on the environment — part (c) (pollution reduction, sustainable practices)

▶️ Answer/Explanation

Solution

(a)

Explanation: Selective breeding involves a deliberate process to enhance desirable traits. To produce fish that grow rapidly, fish farmers would first identify and select parent fish that already exhibit fast growth rates. These selected fish are then bred together. From their offspring, the fastest-growing individuals are again selected to be the parents for the next generation. By repeating this process over many generations, the alleles (gene variants) responsible for rapid growth become more common in the population, leading to a stock of fish that consistently grows quickly.

(b)

Explanation: The conversion of ammonia to nitrates is a natural biological process called nitrification. This process is carried out by specific types of bacteria known as nitrifying bacteria. These bacteria are autotrophs that obtain energy by oxidizing nitrogen compounds. The process occurs in two main stages. First, bacteria such as Nitrosomonas convert ammonia (NH₃) into nitrites (NO₂⁻). Then, other bacteria, like Nitrobacter, convert these nitrites into nitrates (NO₃⁻). Nitrates are a form of nitrogen that can be more easily utilized by plants and algae.

(c)

Explanation: The multi-trophic level aquaculture system is designed to create a more balanced and efficient ecosystem, which directly addresses pollution and profitability.

Reducing Pollution:

The system significantly reduces solid waste pollution because lobsters and crabs consume the waste food and faeces produced by the main fish stock. This means less organic matter accumulates on the seabed.
With less waste material available, there is a reduction in the population of decomposing bacteria. This is beneficial because these bacteria consume large amounts of oxygen during respiration; therefore, lower bacterial numbers help to maintain higher oxygen levels in the water, preventing oxygen depletion that can kill aquatic life.
Furthermore, the seaweed plays a crucial role in reducing dissolved nutrient pollution. It absorbs nitrates, phosphates, and other minerals from the water that would otherwise act as fertilizers, potentially causing excessive algal growth (algal blooms) and eutrophication. The seaweed also releases oxygen through photosynthesis, further improving water quality.

Increasing Profits:

This system creates additional saleable products. The farmer can now harvest and sell not only the main fish but also the lobsters, crabs, and seaweed, diversifying their income streams.
It also reduces costs. There is no need to purchase extra feed for the lobsters and crabs, as they consume the waste from the fish. Similarly, the seaweed obtains its minerals naturally from the water, eliminating the need for artificial fertilizers.
Healthier fish, resulting from the improved water quality (higher oxygen, lower disease risk), are likely to grow better and have lower mortality rates, leading to higher yields and reduced losses.

Question

Graph 1 shows the mass of fish caught by traditional fishing in tonnes from 1960 to 2016 in three countries.

Graph 2 shows the mass of fish produced by fish farming from 1960 to 2016 in the same three countries.

(a) Comment on the changes in the mass of fish caught by traditional fishing and the mass of fish produced by fish farming from 1960 to 2016.
Use information from the graphs to support your answer.

(b) Explain the methods a fish farmer can use to maximise production of fish.

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 5(a): Food production — part (a), part (b)
• 5.9B: Understand the methods used to farm large numbers of fish to provide a source of protein — part (b)

▶️ Answer/Explanation

Solution

(a)

Answer: The mass of fish caught by traditional fishing increased in all three countries from 1960 to 2016, with the increases being roughly proportional across the countries. The mass of fish produced by fish farming also increased significantly in all three countries over the same period, with Country A showing the most dramatic increase. In Countries A and C, the tonnage produced by fish farming eventually surpassed that caught by traditional fishing, whereas in Country B, the tonnage from traditional fishing remained higher. Country A consistently had the highest production values for both methods.

Detailed Explanation:

When analyzing the graphs, we can observe several key trends. Firstly, looking at Graph 1 (traditional fishing), all three lines for countries A, B, and C trend upwards from 1960 to 2016. This indicates a general increase in the mass of fish caught using traditional methods over this 56-year period. The lines for the three countries appear to rise at a similar rate, suggesting the increases were by almost the same proportion in each country.

Secondly, Graph 2 (fish farming) reveals an even more pronounced upward trend for all three countries. The practice of fish farming has grown substantially. The line for Country A is particularly steep, showing it experienced the greatest growth in farmed fish production among the three. Country C also shows stronger growth in farming compared to Country B.

Thirdly, comparing the two graphs reveals a shift in production methods. For Country A, the tonnage from fish farming (Graph 2) becomes higher than the tonnage from traditional fishing (Graph 1) from a certain point onwards. The same is true for Country C. However, for Country B, the mass from traditional fishing remains greater than that from farming throughout the period shown. Country A is the dominant producer, having the highest values on both graphs for most of the timeline.

It is important to note that the graphs do not provide information on the sustainability of these practices, the specific species of fish involved, or whether the data is adjusted for population size (per capita).

(b)

Answer: Methods include: separating species/sizes to prevent predation; providing high-protein feed in small, frequent quantities; using antibiotics/fungicides to control disease; filtering water to remove waste and dead fish; aerating water to maintain oxygen levels; and using selective breeding or genetic modification to improve yield.

Detailed Explanation:

To maximise fish production in a farmed environment, a fish farmer can employ several specific techniques that control the conditions to favor rapid and healthy growth.

Firstly, managing the fish population is crucial. Different species of fish should be kept separate to prevent them from preying on each other. Similarly, fish of vastly different sizes or ages should also be separated, as larger fish will often eat smaller ones. Using nets or separate tanks can achieve this.

Secondly, diet is a key factor. Fish should be fed a high-protein diet to support fast growth. To prevent excess food from accumulating and decomposing in the water (which pollutes it and reduces oxygen), the food should be provided in small quantities but more frequently.

Thirdly, disease control is essential in the dense populations typical of fish farms. The use of antibiotics (to combat bacterial infections) and fungicides (to combat fungal infections) can help to reduce mortality rates and keep the fish healthy.

Fourthly, maintaining high water quality is vital. This involves filtering the water to remove fish faeces, uneaten food, and algal blooms. Dead fish must be removed promptly to prevent the spread of disease. Furthermore, water must be aerated using pumps or waterfalls to ensure oxygen levels remain high enough to support a large population of fish, especially since warm water holds less oxygen.

Finally, the genetic stock of the fish can be improved. Selective breeding, where fish with desirable traits like fast growth or disease resistance are bred together, can gradually enhance the overall productivity of the farm. In some cases, genetic modification (GM) might be used to introduce such traits more directly.

Question

A scientist uses this method to investigate the effect of water quality on the growth of fish.

fill a pond with filtered water
fill another pond with unfiltered water
place the same mass of fish of the same species in each pond
determine the increase in total mass of fish in each pond after 180 days

The graph shows the scientist’s results.

(a) The mean rate of increase in total mass of the fish in the filtered water is 0.214 kg per day.

Calculate the difference between the mean rate of increase in the total mass of the fish in filtered and unfiltered water.

(b) Unfiltered water contains more bacteria.

Explain why unfiltered water containing more bacteria affects the growth of fish.

(c) Give one biotic variable the scientist controlled in the investigation.

(d) Give a method the scientist could use to control interspecific predation in the ponds.

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 5(a): Food production — Fish farming — parts (b), (d)
• 4(a): The organism in the environment — part (c)
• Appendix 4: Mathematical skills — part (a)

▶️ Answer/Explanation

Solution

(a) 0.056 kg per day

Explanation:

First, we need to find the mean rate of increase for the fish in the unfiltered water. From the graph, the total increase in mass for unfiltered water is 28.5 kg over 180 days.

Mean rate for unfiltered water = Total mass increase / Number of days = 28.5 kg / 180 days = 0.1583 kg/day (approximately 0.158 kg/day).

The mean rate for filtered water is given as 0.214 kg/day.

Difference = Mean rate (filtered) – Mean rate (unfiltered) = 0.214 kg/day – 0.158 kg/day = 0.056 kg/day.

So, the difference in the mean rate of increase is 0.056 kg per day.

(b)

Explanation:

Unfiltered water, containing more bacteria, can negatively impact fish growth in several ways. Firstly, bacteria are living organisms that respire. An increase in bacterial population leads to higher rates of respiration in the water, which consumes more dissolved oxygen. This results in less oxygen being available for the fish.

Secondly, with less oxygen available, the fish cannot respire as effectively. Respiration provides energy for all life processes, including growth. Reduced respiration means less energy is available for growth, leading to a smaller increase in mass.

Finally, some bacteria can be pathogenic (disease-causing). A higher bacterial load increases the risk of the fish contracting diseases, which can damage tissues like the gills (impairing gas exchange) and divert energy away from growth towards fighting infection.

(c) Species / type of fish OR Mass of fish (at the start)

Explanation:

A biotic variable is a living factor. The scientist controlled biotic variables by using the same species of fish and placing the same mass of fish in each pond at the beginning of the investigation. This ensures that any difference in growth is due to the water quality (the independent variable) and not because of differences in the type or initial size of the fish used.

(d) Use a net / cage OR Shoot predators OR Make noise

Explanation:

Interspecific predation is when one species (a predator) hunts and eats another species (the prey). In this case, predators from other species might eat the fish in the ponds. To control this, the scientist could physically separate the fish from potential predators by placing them inside a protective net or cage within the pond. Alternatively, more direct methods like shooting predators or using deterrents like making noise to scare them away could be employed to prevent them from preying on the fish.

Question

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Toystory

Toystory is a bull who was born in 2001. The photograph shows Toystory.

In the world of dairy farming Toystory is a famous bull. He fathered 500 000 offspring but did not mate with any cows. He was able to father so many offspring because his semen was collected and then used to fertilise cows using artificial insemination.

Toystory’s mother was a high milk producer and his father was a popular bull. He was sold for $4 000 by his owner to a specialist breeding company called Genex.

Genex started to collect semen from Toystory when he was four years old. The semen is carefully collected, using a teaser animal and an artificial rubber vagina.

The semen is divided into many separate samples. These samples are put in small straws and frozen in liquid nitrogen. The straws can then be sold and sent to dairy farmers around the world to inseminate their cows. A total of 2.4 million samples of semen from Toystory was sold in more than 50 countries around the world.

Toystory’s reputation grew as the offspring he fathered went on to be high milk producers. His semen straws sold for over $60 each. Bull semen can now be sold as sexed or unsexed samples, with sexed samples being more expensive to purchase.

Toystory was highly valued because his offspring produced large quantities of milk of a desired composition. His semen was effective at getting cows pregnant, his daughters gave birth easily and were strong. He had a rare mix of fertility, genetics and appearance.

One of his daughters sold for $300 000 in 2009. His record number of offspring is unlikely to be beaten. This is because bulls are often retired earlier as new genetic advances are discovered.

(a) Suggest why Genex waited until Toystory was four years old before beginning to collect his semen (line 9).

(b) Explain how the semen from the bull is used to fertilise cows using artificial insemination.

(c) (i) Suggest why the semen is stored in liquid nitrogen (line 13).
(ii) Sexed semen is guaranteed to produce offspring of one sex. Suggest why dairy farmers would prefer to used sexed semen (line 19).

(d) Determine the percentage success of Toystory’s semen samples in producing offspring (line 2 and line 15).

(e) Describe how scientists could investigate which of two bulls is the best to use as a father in dairy farming.

(f) Explain why the composition of milk is important to consumers (line 22).

(g) (i) Scientists are now using cloning to produce animals. Describe the stages that are required to clone a bull.
(ii) Give two advantages of using cloning rather than selective breeding to produce offspring.

Most-appropriate topic codes (Edexcel IGCSE Biology (Modular)):

• 3(a): Reproduction — parts (a), (b), (c)(ii)
• 5(a): Food production — parts (e), (f)
• 5(b): Selective breeding — part (e)
• 5(d): Cloning — parts (g)(i), (g)(ii)
• 2(d): Movement of substances into and out of cells / Practical application — part (c)(i)
• Appendix 3: Mathematical skills — part (d)

▶️ Answer/Explanation

Solution

(a)
• so semen contained sperm / (bull is) (sexually) mature / sperm in semen / gone through puberty / fully developed.

(b)
An explanation that includes two of the following points:
• collect semen / sperm from penis of bull (1)
• insert straw into / inject semen (into cow) (1)
• put (it / semen / sperm) in vagina / uterus / womb / cervix (1)

(c)(i)
• preserve (sperm) / keep (sperm) alive / viable / prevent growth of microorganisms / slow down metabolism.

(c)(ii)
• provide females (produce milk) / will produce cows.

(d)
$ 500\,000 \div 2.4 \text{ million} = 0.2083 $
Percentage = $ 0.2083 \times 100 = 20.83\% $ (allow 1 mark for ÷ 2.4 million).

(e)
A description that makes reference to three of the following points:
• use semen (from each bull) to fertilise (many / similar) cows (1)
• collect / measure milk yields (1)
• from each daughter / offspring of these cows / mother of bull (1)
• select bull with highest (average) milk yield (across all daughters) (1)

(f)
An explanation that makes reference to two of the following points:
• (milk that contains) (most) fat (1)
• (most) protein (1)
• (most) vitamins (1)
• (milk that contains) (most) calcium (1)

(g)(i)
A description that makes reference to four of the following points:
• nucleus from (body) cell of bull (1)
• insert this nucleus into enucleated egg cell (1)
• electric shock (1)
• mitosis / cell division (1)
• embryo into uterus / womb (1)
• surrogate mother (1)

(g)(ii)
An explanation that makes reference to two of the following points:
• genetically identical / no genetic variation / same (combination of) alleles (1)
• quicker process (1)

Edexcel iGCSE Biology 4BI1 - Paper 2B - Food production- Exam Style Questions- New Syllabus

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