4 (1400U30-1) Examiner only 2. Most terrestrial plants use chlorophylls a and b to construct pigment-protein complexes which harvest light. Graph 2.1A shows an absorption spectrum for a terrestrial plant and the Graph 2.1B shows corresponding action spectrum. (a) Describe the relationship between the absorption spectrum and the action spectrum and state a suitable conclusion which explains the relationship. [2] © WJEC CBAC Ltd. 400 500 600 700 400 500 430 640 670 600 700 400 500 600 700 Wavelength / nm Wavelength / nm Wavelength / nm Absorption spectrum Action spectrum chlorophyll a chlorophyll b Rate of photosynthesis / au Absorption / au 04 Graph 2.1A Graph 2.1B (1400U30-1) Turn over. 140 0 U3 01 0 5 5 Examiner only (b) Different taxa contain different photosynthetic pigments. Diatoms are aquatic photosynthetic organisms. Their chloroplasts contain chlorophyll a, but instead of chlorophyll b they contain chlorophyll c. Graph 2.2 shows the absorption spectrum of chlorophyll c. (i) Describe the main difference between the absorption spectrum for chlorophyll b and the absorption spectrum for chlorophyll c. [1] (ii) With reference to the peaks labelled on the action spectrum in Graph 2.1B, predict how the action spectrum for diatoms would differ from that of terrestrial plants. [1] © WJEC CBAC Ltd. Wavelength / nm Absorption / au 400 500 600 700 Graph 2.2 05 6 (1400U30-1) Examiner only Image 2.3 shows the depths that different wavelengths of light are able to penetrate water. Image 2.3 (c) Use information from Graph 2.2 and Image 2.3 to explain why diatoms living at a depth of 200 m have chlorophyll c instead of chlorophyll b. [1] © WJEC CBAC Ltd. Wavelength of light / nm Depth of water / m 06 (1400U30-1) Turn over. 140 0 U3 01 07 7 Examiner only Image 2.4 shows an electronmicrograph of a single diatom. (d) Using information from Image 2.4, classify diatoms into their Domain. Give a reason for your choice. [2] Domain ……………………………………………………………………....…………………………………………………………………………………………………………… Reason …………………………………………………………………………………………………………………………………………………………………………………….. © WJEC CBAC Ltd. 1 µm Image 2.4 chloroplast nucleus 07 8 (1400U30-1) Examiner only (e) Diatoms are responsible for about 40% of marine productivity and because the oceans cover about 70% of the Earth’s surface they make a great contribution to global productivity. Blue whales feed on tiny crustaceans called krill, by filtering seawater through sheets in their mouths called baleen. Krill feed on diatoms. Net primary productivity (NPP) for diatoms has been estimated to be 50 g m –3 day –1 and secondary productivity for krill has been estimated to be 5 g m –3 day –1. Image 2.5 shows a simplified food chain, the numbers shown are in g m –3 day –1. R represents respiration and E represents excretion. (i) Calculate the rate at which krill use diatom biomass for respiration (R). [1] Rate = ……….……….....………. g m –3 day –1 (ii) It is estimated that a single blue whale needs to consume 8 000 kg of biomass per day. The biomass of krill was estimated as 25 g m –3. Calculate the volume of water a whale needs to filter per day to take in 8 000 kg of biomass. Give your answer in standard form. [3] Volume of water = ……….……….....………. m 3 day –1 © WJEC CBAC Ltd. Image 2.5 08 diatoms blue whale krill R E 50 5 11 1 (1400U30-1) Turn over. 140 0 U3 01 0 9 9 Examiner only 3. ATP is described as the universal energy currency of cells. (a) (i) Describe why ATP is described as a universal currency. [2] Image 3.1 summarises the production and use of ATP in muscle cells. (ii) Complete the diagram in Image 3.1. [3] © WJEC CBAC Ltd. Image 3.1 ........................................... + oxygen ............................................................. relaxed muscle ATP .......................... + .......................... carbon dioxide + ............................................. energy energy 09 10 (1400U30-1) Examiner only (b) Image 3.2 shows diagrammatic representations of membranes found in two organelles where ATP synthesis takes place. (i) Name the organelles in which the membranes (shown in Image 3.2) would be found. [1] A ……………………………….………………………………. B ……………………………….………………………………. (ii) In Image 3.2, X, Y and Z represent membranes and compartments found in organelles A and B. Complete the Table 3.3 to name the membranes and compartments represented in Image 3.2 for each organelle. [3] Table 3.3 © WJEC CBAC Ltd. Image 3.2 Name of membrane / compartment Letter Part represented in image Organelle A Organelle B X membrane ......................................................... ......................................................... Y compartment enclosed by membrane ......................................................... ......................................................... Z compartment surrounding membrane ......................................................... ......................................................... 10 Membrane found in organelle B Membrane found in organelle A (1400U30-1) Turn over. 140 0 U3 01 11 11 Examiner only (iii) Describe how the components in the membrane of organelle B are involved in the synthesis of ATP by chemiosmosis. [5] © WJEC CBAC Ltd. 11 12 (1400U30-1) Examiner only The experiment shown in Image 3.4 is considered to be evidence supporting the chemiosmotic hypothesis. It was carried out on membranes isolated from organelles of type A in Image 3.2 and made into vesicles. The isolated membranes were placed in buffer solutions, the lower the pH the higher the concentration of protons. (c) Explain why the experiment shown in Image 3.4 supports the chemiosmotic theory. [4] © WJEC CBAC Ltd. Image 3.4 ATP ADP + Pi H+ pH 4 pH 8 ADP + Pi pH 4 pH 4 membrane isolated from organelle A ATP detected rapid change of external pH to pH 8 placed in buffer pH 4 internal pH equalised with external pH 18 12 (1400U30-1) Turn over. 140 0 U3 01 13 13 Examiner only 4. The size of any population at a given time is determined by the equation: Number of individuals = (birth rate + immigration) – (death rate + emigration) In field studies which monitor population size over a period of time the number of individuals often stays constant. (a) Using the terms in brackets from the above equation, write another equation which shows the relationship between the terms when the population size remains constant. [1] ……………………………………………..…………...................……………. = ……………....…………………………....……..…………...........……………. Scientists monitored the population of frogs in a woodland surrounding a pond. The capture-mark-recapture method was used to determine the number of adult frogs, as follows: • 19 frogs were caught • marked by clipping off one toe • they were then released back into the pond • a week later the scientists collected as many frogs as they could over three consecutive days • the results are shown in Table 4.1 • captured frogs from the three consecutive days were not released until after the third collection. Table 4.1 Result of collections following release of marked frogs © WJEC CBAC Ltd. Date Total no. of frogs captured No. of marked frogs Day 1 48 5 Day 2 45 5 Day 3 50 7 Total 143 17 13 (b) (i) From the figures given in the method and Table 4.1 estimate the total number of frogs in the woodland, using the following formula: [2] Where, • N = number in population • M = number initially captured and marked • n = total number subsequently captured • m = number of marked individuals recaptured. Estimated number of frogs in the woodland = .......................................... N = Mn m 14 (1400U30-1) Examiner only (ii) Explain why the chosen method of marking the frogs might have affected the estimate of the frog population. [1] (c) Between capture and release the adult frogs were kept, ten to a tank, partially submerged in water collected from the pond. The frogs in one of the tanks developed red patches on their legs. The scientists suspected they were suffering from ‘red-leg disease’, caused by the bacterium, Aeromonas hydrophila, a Gram-negative bacillus. The scientists took a swab from the leg of one of the frogs, performed a Gram stain and examined the sample under the microscope. Describe the shape and colour of the bacteria they would have seen if the frog had been suffering from red-leg disease. [2] Shape ………………………………………….............................................………… Colour ………………………………………….............................................………… (d) In order to study the survival rates of the larval stage of the frogs (tadpoles), two smaller ponds of equal volume were created from the existing pond using polyethylene sheets. Pond 1 was stocked with 5000 tadpoles per m3 and pond 2 was stocked with 1000 tadpoles per m3. The scientists took 20 samples of water from each pond every ten days and counted the number of tadpoles in each sample. They used the mean counts to calculate the number of tadpoles per m3. Their results are shown in Graph 4.2, the straight lines drawn in black are tangents to the curves. © WJEC CBAC Ltd. 14 (1400U30-1) Turn over. 140 0 U3 01 15 15 Examiner only © WJEC CBAC Ltd. 0 1000 2000 3000 4000 5000 6000 0 10 20 30 40 50 Pond 2 Pond 1 Graph 4.2 Days after adding tadpoles Mean number of tadpoles per m3 (i) Calculate the rate of decline in number of tadpoles for pond 1 at day 10. Give your answer to two significant figures. [3] Rate of decline …………………..……………..……….. tadpoles m–3 day–1 (ii) Using the information from Graph 4.2 it was concluded that a density-dependent factor was causing the change in the tadpole populations. State the evidence for this conclusion and suggest what the factor might have been. [3] 15 16 (1400U30-1) Examiner only (e) The scientists also carried out a laboratory experiment to investigate the effect of selection on rate of development as measured by body length. They used 3 different tanks, which contained 10 dm3 of water. • Tank 1 – low density (1 tadpole per dm3) • Tank 2 – high density (5 tadpoles per dm3) • Tank 3 – high density with selection against small individuals (two of the smallest tadpoles were removed each week). All tanks were kept under the same environmental conditions. The length of the tadpoles in each tank was measured every 10 days and a mean calculated. The results of the experiment are shown in Graph 4.3 (i) With reference to Graph 4.3, state two conclusions that can be drawn about the effect of density and selection on the rate of development of tadpoles in the three tanks. [2] © WJEC CBAC Ltd. 6 7 8 9 10 11 12 13 14 15 0 10 low density Key: high density high density with selection 20 30 40 50 Graph 4.3 Time / days Mean body length / mm 16 (1400U30-1) Turn over. 17 Examiner only (ii) Another group of scientists said that it was not valid to use the results from tank 2 and tank 3 to make a conclusion about the effect of selection. Suggest why it might not be valid to compare these two tanks and describe how the method could be changed to enable a more valid conclusion to be made. [2] © WJEC CBAC Ltd. 16 17 X Y 18 (1400U30-1) Examiner only 5. The mammalian kidney has a role in two physiological processes, excretion and homeostasis. Image 5.1 shows a single kidney nephron. The strategy that the kidney uses for excretion is ultrafiltration followed by selective reabsorption. (a) (i) Use labelled lines on Image 5.1 to show the sites of: [2] I. ultrafiltration II. selective reabsorption © WJEC CBAC Ltd. Image 5.1 afferent arteriole 18 1 0 0.5 1.0 1.5 2.0 2.5 3.0 2 3 4 5 6 (1400U30-1) Turn over. 19 Examiner only (ii) Structures labelled X and Y in Image 5.1 are involved in homeostasis. Name structures X and Y and the homeostatic process in which they are involved. [2] X …………………………………………………………………………………………………… Y …………………………………………………………………………………………………… Homeostatic process ……………………………………………………………………………………………………...................................... The use of micropipettes has allowed samples of fluid to be withdrawn from specific points along kidney tubules of experimental animals. Samples of filtrate were taken from five positions along the proximal convoluted tubule and the concentrations of urea and chloride ions were measured. The results are shown in Graph 5.2. (b) (i) Use Graph 5.2 to explain the change in concentrations for urea and chloride ions along the tubule. [2] © WJEC CBAC Ltd. Graph 5.2 Distance along proximal convoluted tubule / au From Bowman’s capsule urea chloride Concentration / au 19 1 0 0.5 1 1.5 2.0 2 3 4 5 6 20 (1400U30-1) Examiner only © WJEC CBAC Ltd. The experiment was repeated but concentrations of glucose were measured with and without oligomycin. Oligomycin is a chemical compound that specifically inhibits respiration. The results are shown in Graph 5.3. (ii) Use Graph 5.3, to explain the change in concentration along the tubule for glucose with and without the respiratory inhibitor oligomycin. [4] Graph 5.3 20 Concentration / au From Bowman’s capsule Glucose with oligomycin Glucose Distance along proximal convoluted tubule / au (1400U30-1) Turn over. 21 Examiner only A third experiment was carried out to study how structure X, shown in Image 5.1, is involved in the formation of urine. Image 5.4 shows regions of tubule on either side of structure X. Samples were withdrawn from two locations, 1 and 2. The concentration of sodium ions (Na+) was measured in each location. (c) (i) Explain why these locations were chosen for sampling. [1] (ii) The Na+ concentration in the sample taken from location 1 was higher than the sample taken from location 2. Use your knowledge of the function of both limbs of the structure in Image 5.4 to explain this result. [4] © WJEC CBAC Ltd. Image 5.4 direction of flow direction of flow location 2 location 1 15 21 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE (1400U30-1) 22 © WJEC CBAC Ltd. 22 (1400U30-1) Turn over. 23 Examiner only © WJEC CBAC Ltd. 6. Image 6.1 shows a natural carbon cycle unaffected by human activity. The arrows represent processes which transfer carbon from one form to another. (a) (i) Process W involves the fixation of carbon in green plants. Name the two reactants involved and the enzyme that catalyses this process. [2] Reactants ……………………………………………………………………………………………… ……………………………………………………………………………………………… Enzyme ……………………………………………………………………………………………… (ii) I. On Image 6.1, label one of the arrows with an X to show a process which involves micro-organisms. II. Explain the role of micro-organisms in this process. [2] (iii) Add an arrow labelled C to Image 6.1 to represent the transfer of carbon as a result of human activity. [1] Image 6.1 W carbon dioxide (atmosphere) organic compounds (animals) organic compounds (coal,gas,oil) inorganic compounds (shells) limestone (rocks) carbonates (oceans) organic compounds (plants) organic compounds (dead plants and animals) 23 24 (1400U30-1) © WJEC CBAC Ltd. (b) Nine global systems have been identified as being key regulators of the Earth’s stability. Values have been proposed that represent boundaries or thresholds. Table 6.2 shows two of the nine systems together with their threshold values and current values and Image 6.3 displays the threshold values and current values as a circular graph. Planetary System Parameters Threshold values Current value Climate change Atmospheric carbon dioxide concentration (ppm by volume) 350 387 Nitrogen How much nitrogen is removed from the atmosphere for human use (tonnes × 106 / year) 35 121 biodiversity land use freshwater ocean acidification Z Y aerosol ozone Threshold chemical pollution Image 6.3 Table 6.2 – Planetary Boundaries 24 (1400U30-1) Turn over. 25 Examiner only © WJEC CBAC Ltd. (i) Use the information in Table 6.2 to name the two missing planetary systems labelled Y and Z in Image 6.3. [1] Y ....................................................................... Z ...................................................................... (ii) Use Image 6.3 to state what the two planetary systems in Table 6.2 have in common with each other and with the Land-use system. [1] (c) Explain what is meant by a safe operating space for humanity, describe where that is shown in Image 6.3, and describe the consequences of exceeding planetary boundaries. [3] 10 25 26 (1400U30-1) 7. Image 7.1 shows the pathway from a tooth to an area of the brain which generates the sensation of pain. It also shows the site of action of two local anaesthetics used in dentistry. Image 7.2 shows a reflex arc. © WJEC CBAC Ltd. pain centre brain tooth ganglion ganglion spinal cord spinal cord Site of action of local anaesthetic B which prevents the entry of calcium ions into the presynaptic membrane Site of action of local anaesthetic A which prevents the passage of sodium ions into neurons Image 7.1 Image 7.2 26 (1400U30-1) Turn over. 27 Examiner only Compare and contrast the pathway shown in Image 7.1 with the reflex arc in Image 7.2. Using your knowledge of the generation of action potentials, suggest how anaesthetic A will prevent pain. Using your knowledge of synaptic transmission, suggest how anaesthetic B could also prevent pain. [9 QER] © WJEC CBAC Ltd. 27 28 (1400U30-1) Examiner only © WJEC CBAC Ltd. 28 (1400U30-1) Turn over. 29 Examiner only © WJEC CBAC Ltd. END OF PAPER 29 9 Question number Additional page, if required. Write the question number(s) in the left-hand margin. Examiner only (1400U30-1) 30 © WJEC CBAC Ltd. 30 (1400U30-1) 31 Examiner only Question number Additional page, if required. Write the question number(s) in the left-hand margin. © WJEC CBAC Ltd. 31 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE (1400U30-1) 32 © WJEC CBAC Ltd. 32