Photosynthesis — Paper 4 · IGCSE Science - Combined 0653

4 (a) Fig. 4.1 shows a drawing of a single-celled organism called Euglena as seen using a light microscope. This organism has features of both plants and animals. eyespot chloroplast flagellum nucleus cell membrane Fig. 4.1 (i) Chloroplasts are usually found in plant cells. Describe in detail the function of chloroplasts. … … … … … [3] (ii) Name one feature of Euglena you would more likely see in an animal than a plant. Explain your answer. feature … explanation … … … [2] (b) Fig. 4.2 shows an aquatic food web. Phytoplankton are microscopic plants that float on the surface of the water. Zooplankton are very small animals. seagull fish crab small invertebrates mussel limpet zooplankton seaweed phytoplankton Fig. 4.2 (i) Use Fig. 4.2 to draw a food chain containing five organisms, including the crab. [2] (ii) The chemical energy contained in the producers is transferred through the food web to the seagull as shown in Fig. 4.2. Suggest why the seagull gets more energy transferred from the phytoplankton by eating mussels rather than fish. Explain your answer in detail. … … … … … … [3]

10 marks

Mark scheme: 4(a)(i) contain chlorophyll ; trap light (energy) ; converts (light) into chemical energy ; the idea that chemical energy is contained in glucose / starch / carbohydrate ; 3 4(a)(ii) flagellum ; the idea that the flagellum is for movement ; 2 4(b)(i) food chain containing the following organisms phytoplanktonÆzooplanktonÆmusselÆcrabÆseagull ; four arrows in correct direction in the chain ; 2 4(b)(ii) fewer steps / stages / organisms in chain containing mussels / ora ; use of the term trophic level ; energy is lost at each stage ; by heat / movement / avp ; 3

This question in 0653/41 May/June 2017

7 Fig. 7.1 shows a diagram of the cells in a cross section of a leaf. (a) Most photosynthesis takes place in the palisade cells of the leaf. Complete the balanced symbol equation for photosynthesis. light 6CO2 + 6H2O … + … [1] chlorophyll Z palisade cell stoma Y Fig. 7.1 (b) On Fig. 7.1 (i) draw a line to show a possible path taken by carbon dioxide from point Y to palisade cell Z, [1] (ii) label the tissue that provides water for the leaf. [1] (c) When the stomata are open there is a net movement of water molecules by diffusion out of the leaf. This is called transpiration. Fig. 7.2 shows the area around the stoma of the leaf shown in Fig. 7.1. air air water A molecule B Fig. 7.2 (i) Describe how the water molecules get into the space inside the leaf above the stoma, as shown in Fig. 7.2. … … … [2] (ii) Fig. 7.2 shows a difference in the environment around the leaf in diagram A compared with diagram B. Predict whether the rate of transpiration will be greater in A or B. Explain your answer. … … … [2]

7 marks

Mark scheme: 7(a) C6H12O6 and 6O2 ; 1 7(b)(i) line drawn through stoma to cell Z ; 1 7(b)(ii) xylem correctly labelled ; 1 7(c)(i) by evaporation ; from the surfaces of the mesophyll cells / cells inside the leaf ; 2 7(c)(ii) (greater in A) air around A is less humid than around B / ora ; transpiration happens more slowly if the air is humid / ora ; 2

This question in 0653/43 May/June 2017

7 Fig. 7.1 shows a sealed glass jar containing soil and plants. An oxygen sensor is used to find out how the concentration of oxygen in the glass jar changes during the day. The plants can live in the glass jar for several weeks without opening the jar. bung oxygen sensor glass jar soil Fig. 7.1 (a) The plants in Fig. 7.1 use carbon dioxide for photosynthesis. Explain why they do not run out of carbon dioxide in the sealed jar. … … … [2] (b) The water needed for photosynthesis enters the root hair cells of the plants. Describe how the structure of a root hair cell adapts it for water uptake. … … … … [2] (c) Fig. 7.2 shows a graph of the oxygen concentration in the glass jar shown in Fig. 7.1 over a 12-hour period on a sunny day. oxygen concentration 0600 0800 1000 1200 1400 1600 1800 time / hours Fig. 7.2 Oxygen is produced by photosynthesis taking place in the plant. (i) State a time at which the rate of photosynthesis is highest. Explain your answer. time … explanation … … … [2] (ii) On a different day the graph follows a similar pattern as Fig. 7.2 until 10.00 hours. After 10.00 hours the weather changes and it becomes darker. On Fig. 7.2 draw a line to show how the oxygen production changes after this time. Explain your answer. … … … [2]

8 marks

Mark scheme: 7(a) plants during 7(b) large increa by dif 7(c)(i) any ti maxim 7(c)(ii) line d (rate s produce carbo g respiration ; surface area / e ases rate / efficie ffusion ; me between 10 mum rate of oxy rawn with reduc of) photosynthes on dioxide ; longated shape ency of uptake ; .00 and 13.00 ; gen production / ced gradient afte sis (oxygen prod ; / steepest gradie er 10.00 ; duction) depend ent ; dent on (amount of) light ; max 2 x 2 2 2

This question in 0653/41 Oct/Nov 2017

4 (a) A student does an experiment to investigate the germination of barley seeds. The treatment of the seeds before the experiment is shown in Table 4.1. Table 4.1 seed treatment of seeds before the experiment pH of soaking solution A boiled in water for 10 minutes 7 B soaked at room temperature for a few hours 3 C soaked at room temperature for a few hours 7 • After treatment, a piece of each seed is placed on an agar plate containing starch. • After two days an iodine solution is added to the plate which shows the area of starch remaining on the plate. The results are shown in Fig. 4.1. barley seed barley seed piece piece A B A B blue-black area where starch C remains C area containing starch clear area at the start after a few days Fig. 4.1 The student thinks that an enzyme is produced by the barley seed which causes the starch to be broken down in the clear area. Explain in detail how the results for seed A and seed B, shown in Fig. 4.1, support this idea. seed A … … … seed B … … … [3] (b) Germinating seeds use their store of energy until the young seedlings have chlorophyll in their leaves. Chlorophyll is needed for photosynthesis. Describe the role of chlorophyll in photosynthesis. … … … [2]

5 marks

Mark scheme: 4(a) results show starch present (around A and / or B) ; reference to inactive / denatured enzymes ; because A was boiled / heated ; because B was placed in acid / pH3 / low pH ; max 3 4(b) traps light energy ; converts it to chemical energy / enable carbohydrates / sugar to be formed ; 2

This question in 0653/42 Oct/Nov 2017

7 Fig. 7.1 shows some processes occurring in a forest. clouds water vapour X tree leaves fall onto the soil surface of soil roots Fig. 7.1 (a) Name the process labelled X. … [1] (b) The leaves of the trees contain nutrients in the form of minerals. When the leaves die they fall onto the soil. Organisms in the soil can make the minerals available to the trees again. Name the type of organisms that make the minerals available. Explain your answer. type of organism … explanation … … … [2] (c) The trees in the forest shown in Fig. 7.1 are cut down. Predict and explain the effect of clearing the trees on the amount of rain falling on the forest. … … [1] (d) A storm occurs higher up the hill and water comes flowing down the hill. Suggest how the soil in the cleared area will be affected by water from heavy rainfall flowing down the hill. Explain your answer. … … … [2] (e) The concentration of gases in the atmosphere changes immediately after the trees are cleared. Describe and explain how the concentrations of the following gases change. carbon dioxide … … oxygen … … [2]

8 marks

Mark scheme: 7(a) transpiration ; 1 7(b) decomposers ; break down dead organisms (or their leaves) ; 2 7(c) rainfall reduced because less water is being transpired / evaporated from trees ; 1 7(d) soil will be eroded ; no trees / tree roots to stabilise the soil ; 2 7(e) carbon dioxide increases (no mark) less taken in during photosynthesis ; oxygen decreases (no mark) less given out by photosynthesis ; 2

This question in 0653/43 Oct/Nov 2017

4 Fig. 4.1 shows a cross-section of a leaf. Cells P and Q are examples of mesophyll cells in the leaf. R cell P cell Q S Fig. 4.1 (a) On Fig. 4.1 draw label lines from 1. R to the part of any cell which contains the genetic material, 2. S to a part of tissue that transports water. [2] (b) Cell P is able to carry out photosynthesis at a greater rate than cell Q. Use evidence from Fig. 4.1 to support this statement referring to (i) the position of cell P in the leaf compared with cell Q, … … [1] (ii) the number of chloroplasts in cells P and Q. … … … [2] (c) Describe in detail the function of chlorophyll in chloroplasts. … … … [2]

7 marks

Mark scheme: 4(a) line drawn from R to any nucleus ; line drawn from S to any xylem tube cross section ; 2 4(b)(i) P is nearer to the surface / top so it captures more light ; 1 4(b)(ii) P has more chloroplasts than Q ; chloroplast is the site of photosynthesis ; reference to increased light absorption / increased amounts of chlorophyll ; max 2 4(c) traps light energy ; converts it to chemical energy / for formation of carbohydrates ; 2

This question in 0653/42 Feb/March 2018

4 (a) Fig. 4.1 shows three leaves P, Q and R. The leaves are of similar size. They are all taken from the same type of plant on a sunny day. green yellow P Q R Fig. 4.1 (i) Suggest which leaf traps the most light energy. Explain your answer. leaf … explanation … … [1] (ii) Describe in detail what happens to the light energy that is trapped in the leaves. … … … [2] (b) All cells of plants need a source of glucose for aerobic respiration. (i) State the balanced symbol equation for aerobic respiration. … [2] (ii) Suggest how root cells are supplied with glucose. … … … [2]

7 marks

Mark scheme: 4(a)(i) (leaf P ) it contains most chlorophyll ; 1 4(a)(ii) converted to chemical energy ; used to make glucose / carbohydrate ; 2 4(b)(i) C6H12O6 + 6O2 → 6CO2 + 6H2O correct formulae ; correctly balanced depending on correct formulae ; 2 4(b)(ii) from leaves ; (transport) through the phloem ; 2

This question in 0653/41 May/June 2018

1 (a) Fig. 1.1 shows a diagram of a duckweed plant. Duckweed is found in lakes. The green leaves float on the top of the water and the roots reach down into the water. leaves roots Fig. 1.1 (i) Photosynthesis takes place in the leaves of the duckweed. State the balanced symbol equation for photosynthesis. … [2] (ii) Air is trapped between the cells in the leaves of the duckweed. Suggest how this is an advantage to the survival of the duckweed. … … … [2] (b) An investigation is carried out to find the effect of increased concentration of nitrate ions on the growth of a duckweed population. At the start, dishes A and B each contain lake water and six duckweed plants. Nitrate ions are added to dish B and both dishes are left for five days. The results are shown in Fig. 1.2. duckweed plant dish A dish B at the start dish A dish B after five days Fig. 1.2 (i) Use the information in Fig. 1.2 to describe the difference between the results in dishes A and B after five days. … … … … [2] (ii) State a conclusion that can be drawn from the results seen in Fig. 1.2. … … [1] (c) Some fertiliser containing nitrate ions accidentally enters a lake which has a small number of duckweed plants on the surface. (i) Predict how the surface of the lake changes over the next few weeks. … … [1] (ii) The plants beneath the surface of the lake die. The fish in the lake die too. Describe the role of the lake bacteria in these events. … … … … … [3]

11 marks

Mark scheme: 1(a)(i) 6CO2 + 6H2O C6H12O6 + 6O2 ;; 2 1(a)(ii) makes the leaf float ; good light absorption ; 2 1(b)(i) more plants produced in B than A / greater increase in B than A ; use of supporting data e.g. increase of 5 in A and 19 in B ; 2 1(b)(ii) nitrate ions causes population to increase more rapidly ; 1 1(c)(i) becomes covered with duckweed / algae / plants ; 1 1(c)(ii) (bacteria) decompose the dead plants ; bacteria use up oxygen / oxygen concentration in pond decreases ; due to respiration of the bacteria ; fish die / suffocate due to lack of oxygen ; max 3

This question in 0653/43 May/June 2018

7 A student is investigating photosynthesis in an aquatic plant. (a) Complete the balanced symbol equation for photosynthesis. … + … CO2 … + … O2 [2] (b) Fig. 7.1 shows the apparatus that the student uses in the investigation. after a few hours oxygen bubbles of oxygen test-tube water plant Fig. 7.1 The test-tube is full of water at the start. The apparatus is placed on a laboratory bench and left for a few hours. Explain why the water in the test-tube moves downwards in the test-tube in Fig. 7.1. … … [1] (c) The investigation is repeated in conditions of much greater light intensity. The apparatus is left for the same length of time as before. test-tube water plant Fig. 7.2 (i) On Fig. 7.2 draw a line to suggest the new level of water in the test-tube. [1] (ii) Explain your answer to (c)(i). … … [1] (d) (i) Explain why acid rain reduces the rate of photosynthesis in plants. … … [1] (ii) Describe two measures that can be taken to reduce acid rain. 1. … 2. … [2]

8 marks

Mark scheme: 7(a) 6H2O + 6(CO2) → C6H12O + 6(O2) 1 mark for correct formulae ; 1 mark for balanced (dependent on formulae) ; 2 7(b) oxygen / gas produced (by the plant and displaces water) ; 1 7(c)(i) line (meniscus) drawn on Fig.7.1 at a lower position than in Fig. 7.2 ; 1 7(c)(ii) reference to increased (rate of) photosynthesis ; 1 Question Answer Marks 7(d)(i) due to denaturation of enzymes / damage to leaves / increased soil toxicity ; 1 7(d)(ii) use cleaner / alternative energy sources / reduce usage of fossil fuels ; remove sulfur dioxide from factory emissions ; catalytic converters ; avp ; Max 2 2

This question in 0653/41 Oct/Nov 2018

4 Rainforest is often cleared for agriculture by cutting down the trees and burning them. This process is called ‘slash and burn’. The burning of the trees produces a smoky haze made from very small carbon particles suspended in the air. Fig. 4.1 is a picture of clearing land by slash and burn. smoky haze Fig. 4.1 (a) Suggest how the gas exchange system of a human could be affected by inspiring a large volume of the air containing the carbon particles. … … [1] (b) (i) Some of the suspended carbon particles land on the leaves of crops and trees covering them with a thin layer of carbon. Suggest and explain how this layer of carbon affects the function of chlorophyll in the leaves. … … … … [3] (ii) The concentration of oxygen in the atmosphere decreases in the area where slash and burn is taking place. Suggest two reasons why this happens. 1. … … 2. … … [2] (c) Some human activities cause the concentration of carbon dioxide in the atmosphere to increase. Use words or phrases from the list to complete the sentences about how this can affect the environment. Each word or phrase may be used once, more than once or not at all. acid rain argon gamma global warming infra-red methane nitrogen oxygen ultraviolet Greenhouse gases such as carbon dioxide and … absorb … radiation given out from the Earth. When the concentration of carbon dioxide in the atmosphere increases, more of this radiation is absorbed and eventually released into the atmosphere. This increases … . [3]

9 marks

Mark scheme: 4(a) produces irritation / cough / more mucus production ; 1 4(b)(i) thin layer of carbon reduces the amount of light (energy) reaching leaves / chlorophyll ; (chlorophyll) traps less light (energy) ; less conversion to chemical energy ; reduces rate of photosynthesis ; Max 3 3 4(b)(ii) oxygen used during combustion (of wood) ; oxygen not produced by plants ; 2 4(c) methane ; infra-red ; global warming ; 3

This question in 0653/43 Oct/Nov 2018

7 (a) Fig. 7.1 shows a diagram of a wind-pollinated flower. stamen Fig. 7.1 Describe how the stamen in Fig. 7.1 is adapted for wind-pollination. … … [2] (b) Fig. 7.2 shows two pollen grains. One is from a wind-pollinated flower and the other is from an insect-pollinated flower. They are not drawn to scale. F G Fig. 7.2 Suggest which pollen grain, F or G, comes from a wind-pollinated flower. Give a reason for your answer. pollen grain … reason … … [1] (c) After pollination, fertilisation must take place before seeds can be produced. Describe the difference between pollination and fertilisation. … … … [2] (d) Pollen grains in the flower need energy from photosynthesis in the leaves. (i) Name the cells in the leaf where most photosynthesis takes place. … [1] (ii) Describe how the cells you named in (i) are adapted for photosynthesis. … … [1] (iii) Name the part of the plant that transports sugars. … [1] [Total: 8]

8 marks

Mark scheme: 7(a) hangs outside (of flower) ; so wind can reach it ; 2 7(b) F wind-pollinated – grain is smooth so it travels through the air easily / with less friction ; 1 7(c) pollination – transfer of pollen (from anther to stigma) ; fertilisation – fusion of nuclei ; 2 7(d)(i) palisade (cells) ; 1 7(d)(ii) contain chloroplasts / chlorophyll ; 1 7(d)(iii) in the phloem ; 1

This question in 0653/42 Feb/March 2019

1 Fig. 1.1 shows a bag containing sucrose solution placed in a beaker of water for 20 minutes. The bag acts like the partially permeable membranes in cells. It allows small molecules to pass through. It does not allow larger molecules such as sucrose to pass through. glass rod partially permeable bag bag tied tightly sucrose solution with string water beaker Fig. 1.1 The mass of the bag and its contents shown in Fig. 1.1 increases from 25.6 g to 27.3 g. (a) (i) Calculate the percentage increase in the mass of the bag and its contents. percentage increase = … % [2] (ii) Water molecules move into the bag. Explain in detail why this happens. … … … … [2] (b) Suggest one molecule from the list which is unable to pass through the partially permeable bag. carbon dioxide glucose oxygen nitrogen protein … [1] (c) Water is one of the raw materials needed for photosynthesis. (i) Complete the balanced symbol equation for photosynthesis. light … H2O + … chlorophyll C6H12O6 + … [2] (ii) State two ways in which the plant uses the glucose produced by photosynthesis. 1. … 2. … [2] [Total: 9]

9 marks

Mark scheme: 1(a)(i) 27.3–25.6 = 1.7 ; (1.7) / 25.6 × 100 = 6.64(%) ; 2 1(a)(ii) high water potential outside and low water potential inside bag / higher water potential outside bag / water moves from high to low water potential ; and one of water moves in by osmosis ; use of the term diffusion ; water moves so as to try to equalise water potential ; 2 1(b) protein ; 1 1(c)(i) 6H2O + 6CO2 → C6H12O6 + 6O2 1 mark for formulae ; 1 mark for balancing dependent on formulae ; 2 1(c)(ii) any two of (used) in respiration / release energy ; stored as starch ; avp ; max 2

This question in 0653/41 May/June 2019

4 Plants need a supply of mineral ions which they get from water in the soil. (a) (i) State why plants need magnesium ions. … [1] (ii) Describe the effect on plants if they are deficient in magnesium ions. … [1] (b) Farmers add fertilisers containing nitrate ions to their land. Some of these nitrate ions enter lakes. This can lead to eutrophication. Use words from the list to complete the flow diagram about eutrophication. Each word may be used once, more than once or not at all. consumers death decomposition decrease growth increase producers increase in availability of nitrate ions increase in … of producers increase in decomposition after death of … … in aerobic respiration by decomposers … in dissolved oxygen death of organisms in the water. [4] (c) A student investigates transpiration in leaves. He attaches a piece of blue cobalt chloride paper to the upper surface of a leaf. Another piece is attached to the lower surface. Cobalt chloride paper changes colour from blue to pink when water is present. The cobalt chloride paper on the lower surface of the leaf turns pink before the cobalt chloride paper on the upper surface. (i) Explain the result in terms of leaf structure. … … … [2] (ii) The experiment is repeated in a warmer environment. The cobalt chloride paper on the lower surface turns pink more quickly than before. Explain in detail why this happens. … … … [2] [Total: 10]

10 marks

Mark scheme: 4(a)(i) to make chlorophyll ; 1 4(a)(ii) leaves turn yellow ; 1 4(b) growth ; producers ; increase ; decrease ; 4 4(c)(i) faster rate of transpiration / water loss from lower surface / cell surfaces ; more stomata on lower surface ; 2 4(c)(ii) transpiration rate increases / increased evaporation from stomata / mesophyll cell surfaces ; water molecules have more kinetic energy due to higher temperature ; correct reference to diffusion of water molecules / vapour from air spaces in the leaf ; max 2

This question in 0653/43 May/June 2019

4 (a) Plants make glucose by the process of photosynthesis. Complete the balanced symbol equation for photosynthesis. light (i) … CO2 + 6 … C6H12O6 + … [2] chlorophyll (ii) State two uses of the glucose made by photosynthesis. 1. … 2. … [2] (b) Fig. 4.1 shows a diagram of the cross-section of a leaf. The letters refer to the layers of cells in the leaf. A B C D Fig. 4.1 (i) State the letter of the layer of the leaf where the greatest amount of photosynthesis takes place. … [1] (ii) Explain your answer to (i). … … … [2] (c) During transpiration water vapour is lost from leaves through the stomata. When the air surrounding the leaves becomes more humid, the rate of transpiration decreases. Explain why the rate of transpiration decreases. … … … [2] [Total: 9]

9 marks

Mark scheme: 4(a)(i) LHS ; RHS ; 2 4(a)(ii) respiratory substrate / for respiration / to release energy ; to make starch (for storage) ; 2 4(b)(i) B ; 1 4(b)(ii) greatest number of chloroplasts / large amounts of chlorophyll present ; to absorb light / needed for photosynthesis ; 2 4(c) (less transpiration means) less diffusion of water (vapour through the stomata / out of leaf) ; due to increased concentration of water vapour in the air / due to reduced difference in water potential ; 2

This question in 0653/41 Oct/Nov 2019

7 Fig. 7.1 shows the flow of energy through a forest ecosystem. energy from the Sun X producers respiration decomposers primary consumers secondary consumers tertiary consumers Fig. 7.1 (a) (i) Define the term ecosystem. … … … [2] (ii) Complete the sentence about the energy transfer at X. At X … energy is transferred to … energy. [2] (b) The shaded boxes in Fig. 7.1 show the trophic levels in the ecosystem. Energy is lost from the organisms at each trophic level. State two ways in which energy is lost from the organisms at each trophic level. 1. … … 2. … … [2] (c) The trees are the main producers in the forest. They are cut down and taken away from the ecosystem. Suggest what happens to the primary consumers in the forest. Explain your answer. … … … [2] [Total: 8]

8 marks

Mark scheme: 7(a)(i) (a unit containing) all the organisms and their environment ; interacting together ; 2 7(a)(ii) light ; chemical (potential) energy ; 2 7(b) any two from: death of organisms ; (excretion of) waste products from organisms ; respiration ; heat ; 2 7(c) die / become extinct ; source of food/energy has gone / loss of habitat ; 2

This question in 0653/41 Oct/Nov 2019

1 (a) Fig. 1.1 shows an incomplete food web of some organisms in a field. owl fox snake rabbit rat beetle grass and flowering plants Fig. 1.1 (i) The beetle feeds on grass and flowering plants. The snake and owl both feed on the beetle. Use this information to draw arrows to complete the food web in Fig. 1.1. [2] (ii) Name an organism in the food web in Fig. 1.1 which feeds at the same trophic level as the fox. Explain your answer. organism … explanation … … [2] (b) The grass and flowering plants make their own organic nutrients during photosynthesis. (i) Complete the balanced symbol equation for photosynthesis. light 6H2O + 6 … C6H12O6 + … O2 chlorophyll [1] (ii) Describe the role of chlorophyll in the production of glucose during photosynthesis. … … … [2] (iii) Many glucose molecules may be joined together to form starch. State the function of starch in plants. … [1] (iv) Name one other large molecule made from many glucose molecules joined together. … [1] [Total: 9]

9 marks

Mark scheme: 1(a)(i) arrow drawn correctly from grass and flowering plants to beetle ; arrows drawn from beetle to snake and from beetle to owl ; 2 1(a)(ii) owl / snake ; they are at the third trophic level / they are secondary consumers ; 2 1(b)(i) (6H2O + 6) CO2 → (C6H12O6 +) 6 (O2) CO2 and 6 both correct ; 1 1(b)(ii) absorbs / traps, (sun)light (energy) ; transfers / converts, light energy into chemical energy ; 2 1(b)(iii) storage (of energy) ; 1 1(b)(iv) glycogen ; 1

This question in 0653/42 Feb/March 2020

1 (a) Fig. 1.1 represents a plant cell. Fig. 1.1 Add labels to Fig. 1.1 to name two structures that are only present in plant cells. [2] (b) Fig. 1.2 represents an animal cell from the trachea. Fig. 1.2 Describe how the structure of this cell is adapted to its function. … … … [2] (c) Fig. 1.3 shows part of a food web. foxes frogs owls stoats spiders rabbits voles insects grass Fig. 1.3 (i) Define the term consumer. … … [1] (ii) List all of the tertiary consumers shown in the food web in Fig. 1.3. Explain how you identified these consumers using the term trophic level. tertiary consumers … … explanation … … [2] (iii) Complete the food chain containing five organisms from the food web in Fig. 1.3. grass [1] (iv) Describe what the arrows in the food chain represent. … [1] (d) Use words from the list to complete the sentences about photosynthesis. chemical chlorophyll cytoplasm glucose light oxygen starch thermal Each word may be used once, more than once or not at all. During photosynthesis … energy is transferred into … energy by … molecules. [2] [Total: 11]

11 marks

Mark scheme: 1(a) any two of the following correctly labelled: chloroplast ; (large) vacuole ; cell wall ; 2 1(b) (presence of) cilia ; move mucus ; 2 1(c)(i) an organism that gets its energy by feeding on other organisms ; 1 1(c)(ii) (tertiary consumers) foxes and frogs and owls ; (explanation) organisms are at the fourth trophic level ; 2 1(c)(iii) (grass) insects spiders frogs foxes ; 1 1(c)(iv) transfer of energy ; 1 1(d) light (energy is transferred into) chemical (energy) ; chlorophyll ; 2

This question in 0653/42 May/June 2020

1 (a) Fig. 1.1 is a diagram of parts of the alimentary canal and associated organs. X stomach Fig. 1.1 (i) Identify the part labelled X on Fig. 1.1. … [1] (ii) State two functions of hydrochloric acid in the stomach. 1 … … 2 … … [2] (iii) Name the two types of digestion that occur in the alimentary canal. … and … [1] (b) Plants use photosynthesis to produce glucose. (i) Complete the word equation for photosynthesis. light … + water glucose + … … [2] (ii) Glucose is converted to a different carbohydrate for storage in the leaf. This means a leaf can be tested with iodine solution to show that photosynthesis has taken place. Explain why iodine solution can be used to show photosynthesis has taken place. … … … … [2] (c) Fig. 1.2 is a graph showing the effect of light intensity and temperature on the rate of photosynthesis. 30 °C rate of 20 °C photosynthesis light intensity Fig. 1.2 Describe the patterns shown in Fig. 1.2. … … … … [2] [Total: 10]

10 marks

Mark scheme: 1(a)(i) liver ; 1 1(a)(ii) kill bacteria ; provide acidic pH for enzymes ; 2 1(a)(iii) chemical (digestion) AND mechanical (digestion) ; 1 1(b)(i) (light) carbon dioxide + (water) (glucose) + oxygen chlorophyll ;; one mark for carbon dioxide and oxygen one mark for chlorophyll 2 1(b)(ii) iodine (solution) tests for starch / shows blue-black with starch ; glucose made in photosynthesis is converted to starch ; 2 1(c) as light intensity increases so does (rate of) photosynthesis (then it levels off) ; idea that rate is higher, at 30°C than 20°C / at higher temperature ; 2

This question in 0653/42 Feb/March 2021

1 (a) Fig. 1.1 is a diagram of a human sperm cell. nucleus Fig. 1.1 (i) State the function of the nucleus. … [1] (ii) State one way the sperm is adapted to its function in reproduction. … [1] (iii) Name the part of the male reproductive system that makes sperm. … [1] (b) Fig. 1.2 shows two different types of cells from the leaf of a plant. stoma nucleus cytoplasm epidermal cell X nucleus Fig. 1.2 (i) Identify the cells labelled X in Fig. 1.2. … [1] (ii) Identify one structure in cell X in Fig. 1.2 that is absent from a sperm cell. … [1] (c) A student investigates the effect of light intensity on the rate of photosynthesis in an aquatic plant. Fig. 1.3 shows the apparatus the student uses. bubbles of gas lamp water ruler aquatic plant Fig. 1.3 The student: • places the lamp 10 cm from the beaker • counts the number of bubbles the aquatic plant produces in 3 minutes • repeats the count two more times at this distance • then repeats the experiment with the lamp at different distances from the beaker. Table 1.1 shows the results. Table 1.1 distance of lamp number of bubbles average from beaker number of / cm attempt 1 attempt 2 attempt 3 bubbles 10 120 118 123 120 20 118 120 119 119 30 80 78 75 78 40 48 45 42 45 50 15 12 14 (i) Calculate the average number of bubbles when the lamp is 50 cm from the beaker. Give your answer to the nearest whole number. … bubbles [2] (ii) Describe the effect of light intensity on the rate of photosynthesis shown in Table 1.1. … … … … [2] (d) Explain the role of chlorophyll in photosynthesis. … … … [2] [Total: 11]

11 marks

Mark scheme: 1(a)(i) contains genetic material ; 1 1(a)(ii) has a flagellum / presence of enzymes ; 1 1(a)(iii) testes ; 1 1(b)(i) guard cell ; 1 1(b)(ii) chloroplast / cell wall ; 1 1(c)(i) (15 + 12 + 14) ÷ 3 ; (=) 14 (bubbles) ; 2 1(c)(ii) as light intensity increases or distance decreases the rate increases ORA ; the idea that the rate levels off (closer than 20 cm) ; 2 1(d) any two from: absorbs light (energy) ; (transfers) light to chemical energy ; for the synthesis of carbohydrates ; 2

This question in 0653/41 May/June 2021

4 (a) Fig. 4.1 is a graph showing the effect of temperature on the activity of an enzyme. 18 16 14 12 enzyme 10 activity / arbitrary 8 units 6 4 2 0 45 50 55 60 65 70 75 temperature / °C Fig. 4.1 (i) Identify the temperature when this enzyme is most active. … °C [1] (ii) Explain why enzyme activity increases between 45 °C and 55 °C in Fig. 4.1. … … … … [2] (b) Protease enzymes are found in the stomach of humans. (i) State the role of protease enzymes in the stomach. … … … [2] (ii) Fig. 4.2 shows how changing pH affects the activity of three enzymes, A, B and C. A B C enzyme activity 1 7 14 pH Fig. 4.2 Describe the evidence from Fig. 4.2 that shows that enzyme A is the protease enzyme from the stomach. … … … [2] (c) The process of photosynthesis occurs in plants. Complete the balanced equation for photosynthesis. light … CO2 + … … … + … O2 chlorophyll [2] [Total: 9]

9 marks

Mark scheme: 4(a)(i) 60 (°C) ; 1 4(a)(ii) correct reference to gain of energy ; increase in frequency of collisions / more effective collisions ; 2 4(b)(i) break down proteins ; to form amino acids ; 2 4(b)(ii) stomach, is acidic / has a low pH ; only enzyme A works, in acidic conditions / at low pH ; 2 4(c) (light) 6(CO2) + 6H2O C6H12O6 + 6(O2) ;; (chlorophyll) reactants correct = 1 mark products correct = 1 mark 2

This question in 0653/42 May/June 2021

7 (a) A student investigates the effect of light intensity on the rate of photosynthesis of an aquatic plant submerged in a beaker of water. During photosynthesis, the aquatic plant produces bubbles of gas. The student shines a lamp on the aquatic plant from different distances and measures the volume of gas produced in 3 minutes. Table 7.1 shows the results. Table 7.1 distance of lamp volume of gas rate of gas from aquatic plant produced in 3 minutes produced / cm / cm3 / cm3 per second 50 0.2 40 0.8 0.004 30 1.6 0.009 20 2.2 0.012 10 2.2 0.012 (i) Calculate the rate of gas produced when the lamp is 50 cm from the aquatic plant. … cm3 per second [2] (ii) Describe the effect of light intensity on the rate of photosynthesis shown by the results in Table 7.1. … … … … [2] (b) The student does a different experiment to investigate the effect of temperature on the rate of photosynthesis. Fig. 7.1 shows a graph of the results. rate of photosynthesis 0 5 10 15 20 25 30 35 temperature / °C Fig. 7.1 The process of photosynthesis is controlled by enzymes. Explain the shape of the graph seen in Fig. 7.1. Use ideas about enzymes in your answer. … … … … … … [3] (c) Glucose is a product of photosynthesis. Complete these sentences about the uses of glucose in a plant. Choose words from the list. Each word may be used once, more than once or not at all. glycogen mesophyll phloem protein starch xylem Glucose is converted to sucrose and transported to the roots in … vessels. In the roots, the sucrose is converted to … for storage. [2] (d) Plant shoots grow towards a light source. (i) State the name of this tropic response of plants to light. … [1] (ii) State the name of the chemical involved in this response. … [1] [Total: 11]

11 marks

Mark scheme: 7(a)(i) 0.2 ÷ 180 ; 0.001 (cm / s) ; 2 7(a)(ii) as light intensity increases, the rate of photosynthesis increases ; idea that rate levels off (below 20 cm) ; 2 7(b) any three from: 0 to 30 °C rate increases as enzymes gain more kinetic energy ; 0 to 30 °C rate increases as there are more (effective) collisions ; above 30 °C enzymes denature / shape of active site changes ; above 30 °C substrate no longer fits into active site ; 3 7(c) phloem ; starch ; 2 7(d)(i) phototropism ; 1 7(d)(ii) auxin ; 1

This question in 0653/42 Oct/Nov 2021

7 (a) A student uses the apparatus in Fig. 7.1 to investigate the effect of temperature on the rate of photosynthesis of an aquatic plant. During photosynthesis, the aquatic plant produces bubbles of gas. The rate of bubbles produced shows the rate of photosynthesis. thermometer bubble of gas light source water at 25 °C aquatic plant constant distance 0 10 20 30 40 50 60 Fig. 7.1 The student counts the number of bubbles produced by the aquatic plant in 3 minutes. The student does this two more times and calculates the average number of bubbles. The student then repeats the investigation at different temperatures of water. Table 7.1 shows the results. Table 7.1 temperature number of bubbles produced in 3 minutes of water / °C experiment 1 experiment 2 experiment 3 average 25 56 64 59 60 30 75 78 83 79 35 98 93 97 96 40 78 81 76 78 45 20 21 19 20 (i) Describe the effect of temperature on the rate of photosynthesis shown by the results in Table 7.1. … … … [2] (ii) The process of photosynthesis is controlled by enzymes. Explain the result at 45 °C in Table 7.1. Use ideas about enzymes in your answer. … … … [2] (b) Fig. 7.2 shows a cross-section of a leaf of a plant. Y Fig. 7.2 (i) On Fig. 7.2, draw a label line and the letter X to identify cells adapted to synthesise most of the carbohydrates made by the leaf. [1] (ii) State the function of the part labelled Y in Fig. 7.2. … [1] (iii) Explain why a deficiency in magnesium ions results in a reduction in the synthesis of carbohydrates. … … … … … [3] [Total: 9]

9 marks

Mark scheme: 7(a)(i) as temperature increases so does the rate ; rate decreases above 35 °C ; 2 7(a)(ii) enzymes denature / shape of active site changes ; substrate no longer fits into active site ; 2 7(b)(i) any palisade cell labelled ; 1 7(b)(ii) gas exchange ; 1 7(b)(iii) any three from: magnesium ions needed to make chlorophyll ; (deficiency means) less chlorophyll will be made ; (less chlorophyll means) less light energy transferred to chemical energy ; idea that the chemical energy is in the form of carbohydrates (so less are made) ; 3

This question in 0653/43 Oct/Nov 2021

1 (a) Fig. 1.1 shows part of a food web. python jaguar monkey macaw parrot banana tree not to scale Fig. 1.1 (i) Construct a food chain using Fig. 1.1 that includes the macaw. … [2] (ii) Describe how energy is transferred from the banana tree to the jaguar. … … … [2] (b) The leaves of a banana tree contain parts with different functions. The different parts have features that help them with their function. Table 1.1 shows some of the parts of the leaf, their feature and their function. Complete Table 1.1. Table 1.1 part of leaf feature function palisade mesophyll photosynthesis layer … spongy mesophyll air spaces layer … xylem hollow tissue … [3] (c) Fig. 1.2 is a graph showing the effect of light intensity on the rate of photosynthesis. rate of photosynthesis light intensity Fig. 1.2 Describe the effect of light intensity on the rate of photosynthesis in Fig. 1.2. … … … [2] [Total: 9]

9 marks

Mark scheme: 1(a)(i) banana tree → macaw → python ;; one mark for correct order one mark for arrows in correct direction 1(a)(ii) banana eaten by monkey and/or parrot ; monkey and/or parrot eaten by jaguar ; 2 1(b) part of leaf feature function palisade mesophyll layer (many) chloroplasts (photosynthesis) spongy mesophyll layer (air spaces) gas exchange xylem tissue (hollow) transport of water / support ;;; 3 1(c) as light intensity increases the rate of photosynthesis increases ; then levels off / owtte ; 2

This question in 0653/42 Feb/March 2022

7 Fig. 7.1 shows a food chain from a pond. fish frog shrimp pond weed not to scale Fig. 7.1 (a) Identify the organism at the second trophic level in Fig. 7.1. … [1] (b) Sewage containing high levels of nitrate gets into the pond. Explain why a high concentration of nitrate in the pond may result in the death of animals in the food chain. … … … … … … [4] (c) Sewage damages the ecosystem. Increasing carbon dioxide concentration in the atmosphere also damages ecosystems. Explain why planting more trees reduces the carbon dioxide concentration in the atmosphere. … … … [2] [Total: 7]

7 marks

Mark scheme: 7(a) shrimp ; 1 7(b) any four from: increased growth of, producers / pond weed / plants ; blocks light / reduced photosynthesis (of plants below surface) ; death of, producers / pond weed / plants ; decomposition of, producers / pond weed / plants ; increased (aerobic) respiration by decomposers / bacteria / microorganisms ; reduction in oxygen levels ; AVP ; 4 7(c) plants take in carbon dioxide ; reference to photosynthesis ; 2

This question in 0653/43 May/June 2022

1 (a) Fig. 1.1 is a diagram of a wind-pollinated flower. A B Fig. 1.1 (i) State the names of the parts labelled A and B on Fig. 1.1. A … B … [2] (ii) On Fig. 1.1, draw a label line and the letter X to identify the part that produces ovules. [1] (iii) Describe two adaptations for wind pollination of the flower shown in Fig. 1.1. 1 … 2 … [2] (b) Fig. 1.2 shows a food web. wolf coyote vole elk grass Fig. 1.2 (i) Use Fig. 1.2 to construct one food chain that contains the vole. … [2] (ii) Identify one organism in Fig. 1.2 that is on the third trophic level. … [1] (iii) Identify one organism in Fig. 1.2 that is a primary and a secondary consumer. … [1] (c) Grass photosynthesises. State the balanced chemical equation for photosynthesis. … [2] [Total: 11]

11 marks

Mark scheme: Question Answer Marks 1(a)(i) A stigma ; 2 B anther ; 1(a)(ii) ovary labelled ; 1 1(a)(iii) any two from: 2 stigma feathery ; anther outside (flower) ; no petals ; 1(b)(i) grass → vole (→ coyote) → wolf 2 correct order of organisms ; arrows in correct direction ; 1(b)(ii) coyote / wolf ; 1 1(b)(iii) coyote ; 1 1(c) 6H2O + 6CO2 → C6H12O6 + 6O2 2 correct substrates (in either order) ; correct products (in either order) ;

This question in 0653/43 Oct/Nov 2022

7 (a) Two young potted plants are left to grow in a room with no light. Plant A is placed standing upright. Plant B is placed on its side. Fig. 7.1 shows the two plants after 10 days. plant A plant B pale yellow leaves stem bends upwards Fig. 7.1 (i) Lack of light causes the leaves to turn yellow. Complete the sentences. The yellow colour of the leaves in Fig. 7.1 is due to a decrease in the green pigment called … . Less light energy is converted to … energy in the chloroplasts. This results in reduced synthesis of … . [3] (ii) Explain why the stem of plant B bends upwards. … … … … [3] (b) Fig. 7.2 shows part of a plant root. X Fig. 7.2 Describe how the cell labelled X is adapted for its function. … … … [2] (c) During eutrophication aquatic plants die. This decreases the concentration of dissolved oxygen in lakes. One reason for this is a reduction in photosynthesis. Explain one other way the death of aquatic plants reduces the concentration of dissolved oxygen in lakes. … … … … [2] [Total: 10]

10 marks

Mark scheme: 7(a)(i) chlorophyll ; chemical ; carbohydrates ; 7(a)(ii) any three from: responds to gravity / gravitropism ; auxin is produced at the shoot tip ; increased (concentration of) auxin on underside (of stem) ; auxin causes cell elongation ; 3 7(b) large surface area ; increased absorption of, water / mineral (ions) ; 2 7(c) decomposers feed on / break down, (aquatic) plants ; (aerobic) respiration of decomposers (uses oxygen) ; 2

This question in 0653/41 May/June 2023

4 (a) Fig. 4.1 shows a student’s diagram of a cross-section through a leaf. A E B C D Fig. 4.1 The student uses Table 4.1 to show the functions of some of the leaf parts labelled in Fig. 4.1. Complete Table 4.1. Table 4.1 letter name of part function A photosynthesis D phloem cell [3] (b) Plants use light energy in photosynthesis. (i) Complete the balanced equation for photosynthesis. … H2O + … CO2 … + … … [2] (ii) Fig. 4.2 shows the effect of temperature on the rate of photosynthesis in a species of plant. rate of photosynthesis 0 5 10 15 20 25 30 35 40 45 temperature / °C Fig. 4.2 Photosynthesis is an enzyme-controlled reaction. Explain the effect of a temperature of 45 °C on the rate of photosynthesis in Fig. 4.2. … … … … … [3] (c) Fig. 4.3 shows some of the cells and molecules at the tip of a plant shoot. The plant shoot is placed in a position where the direction of light is constantly from the side as shown in Fig. 4.3. direction of light chemical molecule P Q Fig. 4.3 P shows the plant shoot at the start. Q shows the plant shoot after 2 days. Complete these sentences about the response of the plant shoot to light. The plant shoot is responding to light, this is called … . The response is caused by a chemical made in the shoot tip called … . The chemical stimulates growth by causing greater cell … on the shaded side of the shoot. [3] [Total: 11]

11 marks

Mark scheme: 4(a) letter name of part function (A) palisade (mesophyll cell / layer) (photosynthesis) (D) stoma / stomata to allow gas exchange C (phloem) transport (sucrose / amino acids) ;;; one mark for each correct row 4(b)(i) 6 (H2O)  6 (CO2) ; C6H12O6  6O2 ; 2 4(b)(ii) any three from: photosynthesis stops / slows down ; enzymes denature ; active site changes shape ; substrate no longer fits active site ; 3 4(c) phototropism ; auxin ; elongation ; 3

This question in 0653/42 May/June 2023

4 (a) Fig. 4.1 shows a food web. hawk blackbird thrush caterpillar beetle tree Fig. 4.1 (i) Table 4.1 shows some terms that can be used to describe some of the organisms in Fig. 4.1. Complete Table 4.1 by placing ticks (3) in the boxes to show all the terms used to describe each organism. Table 4.1 primary occupies organism carnivore consumer trophic level 3 blackbird caterpillar hawk thrush [3] (ii) Explain why there are no trophic levels above the hawk. Use ideas about energy in your answer. … … … … [3] (b) Older trees store more carbon than younger trees. Scientists record the total number of trees of different species in two forest ecosystems: • a young forest area where all the trees are less than 20 years old • a mature forest area where all the trees are over 50 years old. Fig. 4.2 shows a bar chart of the results. 70 Key: young forest 60 mature forest 50 40 number of trees 30 20 10 0 red yellow red witch chestnut maple birch oak hazel oak tree species Fig. 4.2 (i) The scientists discover that there is more carbon stored in the young forest area. Use Fig. 4.2 to explain why. … … [1] (ii) Identify the tree species in Fig. 4.2 that is not found in the mature forest area. … [1] (c) Describe how light energy is used in the production of starch in trees. … … … … … [4] [Total: 12]

12 marks

Mark scheme: 4(a)(i) 3 organism carnivore primary consumer occupies trophic level 3 blackbird ✓ ✓ caterpillar ✓ hawk ✓ thrush ✓ ✓ carnivore column ; primary consumer column ; trophic level 3 column ; 4(a)(ii) any three from: 3 hawk is trophic level 4 / idea that next level is trophic level 5 ; not enough energy (to support another level) ; energy lost between each trophic level OR only a percentage of energy is transferred between trophic levels ; example of energy loss ; 4(b)(i) greater number of trees in the young forest area ; 1 4(b)(ii) red oak ; 1 4(c) glucose converted to starch / glucose is stored as starch ; 4 plus any three from: (light energy is) transferred to chemical energy ; by chlorophyll ; (takes place in) chloroplasts ; used in photosynthesis ; used to synthesise carbohydrates / glucose ; AVP ;

This question in 0653/42 Oct/Nov 2023

4 (a) A student draws diagrams to show the position of xylem in different parts of a plant. Fig. 4.1 shows the student’s drawings. leaf xylem root xylem stem xylem phloem Fig. 4.1 The student made errors in labelling the drawings. Identify two errors made by the student in Fig. 4.1. 1 … 2 … [2] (b) Fig. 4.2 shows the effect of humidity on transpiration in plants. P rate of transpiration Q humidity Fig. 4.2 Explain the pattern shown in Fig. 4.2 between P and Q. … … … … … … [3] (c) Plants produce carbohydrates by the process of photosynthesis. (i) State the balanced symbol equation for photosynthesis. … [2] (ii) State the name of the cell structure where photosynthesis occurs. … [1] (d) Fig. 4.3 shows a food web for an area in Alaska. polar bear Arctic wolf snowy owl Arctic fox Arctic hare lemming reindeer musk ox lichen grass Fig. 4.3 Table 4.1 shows some information about two of the organisms in Fig. 4.3. Complete Table 4.1. Table 4.1 organism trophic level feeding relationship gets its energy by eating musk ox … … gets its energy by eating snowy owl … and … and … … [3] [Total: 11]

11 marks

Mark scheme: 4(a) root and stem labels are the wrong way around ; 2 xylem label incorrect in leaf ; 4(b) any three from: 3 (description of trend) increased humidity causes decrease in rate of transpiration / ref to inverse relationship between humidity and transpiration rate ; higher humidity means higher water (vapour) concentration in air (surrounding the leaf) ; the idea that at higher humidity the concentration gradient between the leaf and the air is reduced ; reference to reduced, evaporation / diffusion (from leaf at higher humidity) ; 4(c)(i) 6CO2 + 6 H2O ; 2 C6H12O6 + 6O2 ; 4(c)(ii) chloroplast ; 1 4(d) 3 trophic organism feeding relationship level musk ox 2 (gets its energy by eating) grass (gets its energy by eating) snowy owl 3 and 4 (Arctic) fox and (Arctic) hare ;;; correct trophic levels = [1] grass = [1] (Arctic) fox and (Arctic) hare = [1]

This question in 0653/42 Feb/March 2024

4 (a) A student labels a diagram of a plant cell. Fig. 4.1 shows the student’s diagram. cell wall cytoplasm vacuole nucleus Fig. 4.1 (i) The student has not labelled the diagram correctly. Circle all the labels on Fig. 4.1 that are not correct. [1] (ii) Explain how the cell in Fig. 4.1 is adapted to its function. … … … [2] (b) Fig. 4.2 shows the effect of carbon dioxide concentration and light intensity on the rate of photosynthesis. 0.13% CO2 rate of photosynthesis 0.03% CO2 light intensity Fig. 4.2 (i) Describe the effect of increasing light intensity on the rate of photosynthesis as shown in Fig. 4.2. … … … [1] (ii) Trees in a forest are cut down and burnt where they fall. Use Fig. 4.2 to suggest why the rate of photosynthesis in the surrounding plants increases. … … … … [2] (c) Explain why the leaves of plants deficient in magnesium change from green to yellow. … … … … [2] [Total: 8]

8 marks

Mark scheme: 4(a)(i) vacuole and cytoplasm circled ; 1 4(a)(ii) large surface area / elongated shape ; increases, rate of absorption / uptake of water / uptake of mineral (ions) ; 2 Question Answer Marks 4(b)(i) (as light intensity increases) rate of photosynthesis increases, and then levels off / is constant ; 1 4(b)(ii) more light / less competition for light ; more CO2 / less competition for CO2 / CO2 is released by combustion ; 2 4(c) magnesium is required to make chlorophyll ; chlorophyll is a green pigment ; 2

This question in 0653/42 May/June 2024

4 (a) Fig. 4.1 is a graph showing the effect of humidity on the rate of transpiration in a plant. rate of transpiration humidity Fig. 4.1 Explain the shape of the graph shown in Fig. 4.1. … … … … … [3] (b) Plants require light for photosynthesis. Complete the balanced symbol equation for photosynthesis. … CO2 + … H2O … + … O2 [2] (c) A scientist investigates phototropism in two plant shoots, A and B. The scientist covers the tip of shoot A with material that allows light to pass through. The scientist covers the tip of shoot B with material that blocks light. The shoots are left to grow in light coming from one direction only. Fig. 4.2 shows the results. material that allows material that direction light to pass through blocks light of light lighter darker side side shoot A shoot B Fig. 4.2 Complete these sentences to explain the results. More light passes through the material on shoot A on the lighter side than on the darker side. This causes an … distribution of auxin in shoot A. Auxin stimulates more growth by cell … on the darker side of shoot A. Shoot B does not respond to the light because auxin is only made in the … of the shoot. [3] [Total: 8]

8 marks

Mark scheme: 4(a) any three from: 3 increasing humidity causes decrease in transpiration rate ; concentration / percentage of water outside leaf increases ; reduces (water) concentration gradient ; reduces (rate of), diffusion / evaporation ; 4(b) 6 CO2 + 6H2O C6H12O6 + 6O2 2 correct formula for glucose ; equation correctly balanced dependent on glucose formula ; 4(c) unequal / AW ; 3 elongation ; tip / AW ;

This question in 0653/41 Oct/Nov 2024

3 (a) Fig. 3.1 shows a cross-section of a leaf. Q P Fig. 3.1 (i) Name the type of cell labelled P in Fig. 3.1. … [1] (ii) The cell labelled Q is specialised for a specific function. State the function of the cell labelled Q. … [1] (b) Root hair cells take in water and mineral ions from the soil. Root hair cells are adapted for the uptake of mineral ions by having high numbers of mitochondria in their cytoplasm. Explain why large numbers of mitochondria are important for the uptake of mineral ions. … … … … … [3] (c) Fig. 3.2 is a diagram of a plant cell that has been immersed in a sugar solution. Fig. 3.2 Complete these sentences about the cell in Fig. 3.2. Water has left the cell because the sugar solution has a lower water … than that of the cell. The loss of water reduces the … pressure inside the cell. The cell membrane moves away from the cell wall and the cell becomes … . [3] [Total: 8]

8 marks

Mark scheme: 3(a)(i) guard (cell) ; 1 3(a)(ii) photosynthesis ; 1 3(b) any three from: 3 uptake of mineral ions is by active transport ; energy required for, active transport / uptake of mineral ions ; respiration releases energy ; (mitochondria are) site of (aerobic) respiration ; 3(c) potential ; 3 turgor ; plasmolysed ;

This question in 0653/42 Feb/March 2025

2 (a) Fig. 2.1 shows the structure of a plant root. F G Fig. 2.1 (i) Identify the parts labelled F and G in Fig. 2.1. F … G … [2] (ii) Complete the sentences about cell F in Fig. 2.1, to describe how the cell is adapted to its function. Cell F is adapted to its function by having a large … . This adaptation increases the uptake of water and … . [2] (b) Water is lost from the leaves of a plant by the process of transpiration. A student investigates the effect of wind speed on the rate of transpiration. Complete Fig. 2.2 by: • labelling the y-axis • drawing a line to predict the expected results of this investigation. wind speed Fig. 2.2 [2] (c) Plants use water in the process of photosynthesis. Describe the process of photosynthesis. … … … … … [3] [Total: 9]

9 marks

Mark scheme: 2(a)(i) (F) root hair (cell) ; 2 (G) xylem ; 2(a)(ii) surface area ; 2 mineral ions ; 2(b) y-axis labelled as rate of transpiration ; 2 line constantly increasing / constantly increasing then levelling off ; 2(c) any three from: 3 (requires) carbon dioxide / CO2 and water / H2O ; (requiring presence of) chlorophyll ; light energy converted to chemical energy ; (synthesis of), carbohydrates / glucose / C6H12O6 and oxygen / O2 formed (as a by product) ;

This question in 0653/42 May/June 2025

2 (a) Fig. 2.1 is a diagram of a cross-section through a leaf. G F A B C D E Fig. 2.1 State the letter on Fig. 2.1 that identifies: cuticle … a cell specialised for photosynthesis … a cell that transports mineral ions to the leaf. … [3] (b) A green pigment is needed for photosynthesis. State the name of this pigment and its role in photosynthesis. name … role … … … … [3] (c) The graph in Fig. 2.2 shows the effect of temperature on the rate of photosynthesis in a plant. rate of photosynthesis 0 5 10 15 20 25 30 35 40 temperature / °C Fig. 2.2 (i) Identify the optimum temperature for photosynthesis shown in Fig. 2.2. … °C [1] (ii) Enzymes are involved in photosynthesis. Explain the result at 40 °C shown in Fig. 2.2. … … … … … [3] [Total: 10]

10 marks

Mark scheme: 2(a) G ; 3 A ; B ; 2(b) chlorophyll ; 3 transfers light energy to chemical energy ; to synthesise / produce, carbohydrates / glucose ; 2(c)(i) 25 (°C) ; 1 2(c)(ii) enzymes denature (at high temperature) ; 3 active site changes shape ; active site no longer complementary to substrate / substrate no longer fits active site ;

This question in 0653/43 May/June 2025

2 (a) Fig. 2.1 shows a plant cell before and after being immersed in a concentrated salt solution. before after Fig. 2.1 (i) State the name of the effect shown in Fig. 2.1. … [1] (ii) The plant cell in Fig. 2.1 is now removed from the salt solution and immersed in pure water for 60 minutes. Explain the effect of being immersed in pure water on the plant cell. … … … … … … [3] (b) Plants photosynthesise to produce the carbohydrate glucose. (i) Glucose is used to make other carbohydrates. Circle all the carbohydrates made from glucose. amino acids amylase cellulose fatty acids glycerol lipase starch [2] (ii) Complete these sentences about photosynthesis in plants. Photosynthesis requires the raw materials … and … . Photosynthesis also requires … from light and the green pigment … . [3] (c) The information in Fig. 2.2 is about organisms in a food chain. • crabs eat starfish • limpets eat algae • sharks eat crabs • starfish eat limpets Fig. 2.2 (i) Construct a food chain using all the organisms in Fig. 2.2. … [2] (ii) Identify the primary consumer in Fig. 2.2. … [1] [Total: 12]

12 marks

Mark scheme: 2(a)(i) plasmolysis ; 1 2(a)(ii) any three from: 3 M1 water enters the cell ; (Direction of water movement) M2 by osmosis ; M3 pure water has a high(er) water potential / low(er) water potential inside cell ; (Reason why water moves as it does) M4 increase in turgor pressure / cell becomes turgid ; 2(b)(i) cellulose ; 2 starch ; 2(b)(ii) carbon dioxide AND water ; 3 energy ; chlorophyll ; 2(c)(i) algae → limpets → starfish → crabs → sharks ;; 2 organisms in correct order arrows in correct direction 2(c)(ii) limpets ; 1

This question in 0653/41 Oct/Nov 2025

1 (a) Fig. 1.1 is a diagram of a cross-section through a leaf. G A F B E C D Fig. 1.1 State the letter on Fig. 1.1 that identifies one of the: stomata … spongy mesophyll cells … cells that transport sucrose. … [3] (b) Plants produce carbohydrates by the process of photosynthesis. State the balanced symbol equation for photosynthesis. … [2] (c) Fig. 1.2 is a graph showing the effect of temperature on the rate of photosynthesis in a plant. 35 30 25 20 rate of photosynthesis / arbitrary units 15 10 5 0 0 5 10 15 20 25 30 35 temperature / °C Fig. 1.2 (i) Calculate the difference in the maximum and minimum rates of photosynthesis shown in Fig. 1.2. difference in rates of photosynthesis = … arbitrary units [2] (ii) Enzymes are involved in photosynthesis. Explain the shape of the graph between 10 °C and 15 °C shown in Fig. 1.2. … … … … … … [3] [Total: 10]

10 marks

Mark scheme: Question Answer Marks 1(a) C ; 3 B ; E ; 1(b) 6CO2 + 6H2O ; 2 → C6H12O6 + 6O2 ; 1(c)(i) 32 – 2 or (max rate = ) 32 seen or (min rate =) 2 seen ; 2 (max difference = ) 30 (arbitrary units) ; 1(c)(ii) increasing temperature / from 10 °C to 15 °C and linked to 3 any three ;;; • increasing rate of photosynthesis • increasing enzyme activity ; • increasing kinetic energy / enzymes move faster ; • more frequency of (enzyme-substrate) collisions ; • more / faster formation of enzyme-substrate complexes ;

This question in 0653/42 Oct/Nov 2025