Name: BIOLOGY B2 TISSUES AND ORGANS. Class: Time: Marks: Comments: Page 1 of 59

Transcription

1 BIOLOGY B2 TISSUES AND ORGANS Name: Class: Time: Marks: Comments: Page of 59

2 In a living organism, the cells are organised into organs, systems and tissues. (a) Use words from the box to complete the list of these structures in order of size. organs systems tissues The smallest structure is at the top of the list and the largest is at the bottom. cells organism () (b) List A gives three tissues found in the human body. List B gives four functions of tissues. Draw a straight line from each tissue in List A to its correct function in List B. List A Tissue List B Function Covers many parts of the body Muscular tissue Contracts to cause movement Glandular tissue Divides by meiosis Epithelial tissue Releases hormones or enzymes (3) (Total 4 marks) Page 2 of 59

3 2 The image below shows some cells in the lining of the stomach. (a) (i) Use words from the box to name structures A and B. cell membrane chloroplast cytoplasm vacuole A... B... (2) What is the function of the nucleus? Tick ( ) one box. To control the activities of the cell To control movement of substances into and out of the cell To release energy in respiration () Page 3 of 59

4 (b) Draw one line from each part of the human body to its correct scientific name. Part of human body Scientific name Layer of cells lining the stomach Stomach Mouth, stomach, intestines, liver and pancreas An organ An organism An organ system A tissue (3) (Total 6 marks) Page 4 of 59

5 3 The diagram below shows the parts of the body that digest and absorb food. It also shows some details about the structure of the stomach. (a) Complete the table to show whether each structure is an organ, an organ system or a tissue. For each structure, tick ( ) one box. Structure Organ Organ system Tissue Stomach Cells lining the stomach Mouth, oesophagus, stomach, liver, pancreas, small and large intestine (2) (b) (i) The blood going to the stomach has a high concentration of oxygen. The cells lining the stomach have a low concentration of oxygen. Complete the following sentence. Oxygen moves from the blood to the cells lining the stomach by the process of.... () Page 5 of 59

6 What other substance must move from the blood to the cells lining the stomach so that respiration can take place? Draw a ring around the correct answer. glucose protein starch () (iii) In which part of a cell does aerobic respiration take place? Draw a ring around the correct answer. cell membrane mitochondria nucleus () (Total 5 marks) 4 Villi are found in some parts of the digestive system. Diagram shows two villi. Diagram (a) Draw a ring around the correct answer to complete each sentence. muscle. (i) Structure A is a nerve. capillary. () Page 6 of 59

7 dialysis. The villi absorb the products of digestion by diffusion. osmosis. () (b) Diagram 2 shows the digestive system. Diagram 2 (i) In which part of the digestive system, X, Y or Z, are most villi found? There are about 2000 villi in each cm 2 of this part of the digestive system. Why is it helpful to have lots of villi? () () (Total 4 marks) Page 7 of 59

8 5 The diagram shows the human digestive system. (a) Heartburn is a burning feeling caused when acid enters the oesophagus. The acid comes from the stomach. (i) Which letter on the diagram shows the stomach? () Name the acid the stomach produces.... () (iii) Medicines taken to treat heartburn contain chemicals that neutralise excess stomach acid. What type of chemical will neutralise stomach acid?... () Page 8 of 59

9 (b) Use words from the box and your own knowledge to describe how carbohydrates are digested. amylase starch sugars (5) (c) Where in the body are the products of digestion absorbed?... () (Total 9 marks) Page 9 of 59

10 6 The diagram in Figure shows a section through the human heart, seen from the front. Figure (a) Draw a ring around the correct answer to complete each sentence. epithelial (i) The wall of the heart is made mostly of glandular tissue. muscular () The resting heart rate is controlled by the pacemaker. The pacemaker is located at position () (iii) If a person s heart rate is irregular, the person may be fitted with an artificial pacemaker. The artificial pacemaker is an electrical device. a pump. a valve. () Page 0 of 59

11 (b) (i) Write a number, 2, 5, 6 or 7, in each of the three boxes to answer this question. Which chamber of the heart: pumps oxygenated blood to the head and body receives deoxygenated blood from the head and body receives oxygenated blood from the lungs? (3) Give the number, 3, 4 or 8, of the valve that closes when the blood pressure in the aorta is greater than the blood pressure in the left ventricle. Write the correct answer in the box. () (c) The diagram in Figure 2 shows one type of artificial heart valve. The plastic ball is in the closed position. Figure 2 This type of artificial valve could be used to replace a faulty valve in the heart. (i) What is the function of valves in the heart? () Page of 59

12 The artificial valve could be used to replace valve 4 shown in Figure. The artificial valve opens to let blood through when the ball is moved towards A. Which end of the valve, A or B, should point towards chamber 5? Explain your answer. (3) (d) (i) The artificial heart valve may cause blood clots to form on its surface. Describe what happens during blood clotting. (2) Read the information in the passage. Replacing a damaged heart valve can dramatically improve the blood circulation and the supply of oxygen to the body s tissues. The operation to replace a heart valve is a long one during which the patient s blood goes through a bypass machine. Sometimes the artificial valve can fail to work. If the surface of the valve becomes rough, small blood clots can form on its surface then break away and be carried around the body by the blood. Page 2 of 59

13 Evaluate the advantages and disadvantages of artificial heart valves. (4) (Total 7 marks) Page 3 of 59

14 7 Leaves are made from layers of cells. The diagram shows a section through part of a leaf. (a) (i) Which word in the table describes layer A? Tick ( ) one box. Layer A Tick ( ) Tissue Organ Cell () Which word describes a whole leaf? Draw a ring around one answer. organ tissue organism () Page 4 of 59

15 (b) (i) Which two layers of cells, A, B, C and D, can photosynthesise? Use information from the diagram to help you. Tick ( ) two boxes. Layer A Layer B Layer C Layer D (2) Give one reason for your answer. () Page 5 of 59

16 (c) List X gives the names of two parts of a cell. List Y gives information about parts of a cell. Draw one line between each part of the cell in list X and information about it in list Y. List X Part of a cell List Y Information Controls the passage of substances into the cell Vacuole Contains the cell sap Nucleus Controls the activities of the whole cell (2) (Total 7 marks) Page 6 of 59

17 8 The diagram shows a section through a plant leaf. (a) Use words from the box to name two tissues in the leaf that transport substances around the plant. epidermis mesophyll phloem xylem... and... () (b) Gases diffuse between the leaf and the surrounding air. (i) What is diffusion? (2) Name one gas that will diffuse from point A to point B on the diagram on a sunny day. () (Total 4 marks) Page 7 of 59

18 9 The diagram below shows a cross-section of a plant root. The transport tissues are labelled. (a) (i) What is tissue A? Draw a ring around the correct answer. cuticle epidermis xylem () Name two substances transported by tissue A (2) (b) Phloem is involved in a process called translocation. (i) What is translocation? () Explain why translocation is important to plants. (2) Page 8 of 59

19 (c) Plants must use active transport to move some substances from the soil into root hair cells. (i) Active transport needs energy. Which part of the cell releases most of this energy? Tick ( ) one box. mitochondria nucleus ribosome () Explain why active transport is necessary in root hair cells. (2) (Total 9 marks) 0 (a) The diagrams show apparatus you could use to mount a piece of leaf epidermis for examination under a microscope. Page 9 of 59

20 (i) Name the pieces of apparatus labelled A, B, C and D on the diagram. A... B... C... D... (4) Describe how you would use A, B, C and D to mount a piece of leaf epidermis for examination under a microscope. (3) Page 20 of 59

21 (b) A student used a grid on a microscope to estimate the number of stomata in some leaf epidermis. The drawings show four of the grid squares the student observed. Each grid has an area of mm 2. (i) Calculate the mean number of stomata per grid square. Mean number of stomata per grid square... (2) Calculate the mean number of stomata per mm 2 of leaf epidermis. Mean number of stomata per mm 2... (2) Page 2 of 59

22 (iii) Each side of a grid square has a length of approximately mm. Use this information to estimate the length of a guard cell. Estimated length of guard cell... mm (2) (c) A group of students looked at stomata on four different species of plant, W, X, Y and Z. The students estimated the number of stomata per cm 2 on the upper and lower surfaces of the leaves of the four species. The results are shown in the table. Plant species Estimated number of stomata per cm 2 of leaf surface Upper surface of leaf Lower surface of leaf W X Y Z (i) Which plant species, W, X, Y or Z, probably lives in a dry region? Explain why you have chosen this species. (3) Page 22 of 59

23 All four species have more stomata on the lower surface of their leaves than on the upper surface. Suggest how this feature could improve the chances of the survival for the plants. (2) (Total 8 marks) The image below shows an epithelial cell from the lining of the small intestine. (a) (i) In the image above, the part of the cell labelled A contains chromosomes. What is the name of part A? () How are most soluble food molecules absorbed into the epithelial cells of the small intestine? Draw a ring around the correct answer. diffusion osmosis respiration () Page 23 of 59

24 (b) Suggest how the highly folded cell surface helps the epithelial cell to absorb soluble food () (c) Epithelial cells also carry out active transport. (i) Name one food molecule absorbed into epithelial cells by active transport. () Why is it necessary to absorb some food molecules by active transport? () Suggest why epithelial cells have many mitochondria. (2) (d) Some plants also carry out active transport. Give one substance that plants absorb by active transport.... () (Total 8 marks) 2 The diagram below shows a single-celled alga which lives in fresh water. Page 24 of 59

25 (a) Which part of the cell labelled above: (i) traps light for photosynthesis () is made of cellulose? () (b) In the freshwater environment water enters the algal cell. (i) What is the name of the process by which water moves into cells? () Give the reason why the algal cell does not burst. () (c) (i) The alga can photosynthesise. Complete the word equation for photosynthesis. water oxygen (2) The flagellum helps the cell to move through water. Scientists think that the flagellum and the light-sensitive spot work together to increase photosynthesis. Suggest how this might happen. (2) Page 25 of 59

26 (d) Multicellular organisms often have complex structures, such as lungs, for gas exchange. Explain why single-celled organisms, like algae, do not need complex structures for gas exchange (3) (Total marks) 3 Diabetes is a disease in which the concentration of glucose in a person s blood may rise to fatally high levels. Insulin controls the concentration of glucose in the blood. (a) Where is insulin produced? Draw a ring around one answer. gall bladder liver pancreas () (b) People with diabetes may control their blood glucose by injecting insulin. (i) If insulin is taken by mouth, it is digested in the stomach. What type of substance is insulin? Draw a ring around one answer. carbohydrate fat protein () Apart from using insulin, give one other way people with diabetes may reduce their blood glucose. () Page 26 of 59

27 (c) The bar chart shows the number of people with diabetes in different age groups in the UK. Age in years (i) Describe how the number of males with diabetes changes between the ages of 0 44 years and 75 years and over. (3) Page 27 of 59

28 Compare the number of males and females with diabetes: between the ages of 0 and 64 years over the age of 65 years. (2) (Total 8 marks) 4 Some students investigated the effect of ph on the digestion of boiled egg white by an enzyme called pepsin. Egg white contains protein. The students: put a glass tube containing boiled egg white into a test tube added a solution containing pepsin at ph 7 set up six more tubes with solutions of pepsin at different ph values left the test tubes for 24 hours at room temperature. The image below shows one of the test tubes, at the start and at the end of the 24 hours. At start 24 hours later (a) (i) Name the product of protein digestion. () Page 28 of 59

29 What type of enzyme digests protein? Tick ( ) one box. amylase lipase protease () (b) The egg white in each tube was 50 mm long at the start of the investigation. The table below shows the students results. ph Length in mm of boiled egg white after 24 hours (i) At which ph did the pepsin work best? ph... () The answer you gave in part (b)(i) may not be the exact ph at which pepsin works best. What could the students do to find a more accurate value for this ph? (2) Page 29 of 59

30 (iii) There was no change in the length of the egg white from ph 5 to ph 7. Explain why. (2) (c) Pepsin is made by the stomach. Name the acid made by the stomach which allows pepsin to work well.... () (Total 8 marks) Page 30 of 59

31 5 Fresh milk is a mixture of compounds including lipid, protein and about 5% lactose sugar. Lactose must be digested by the enzyme lactase, before the products can be absorbed. Lactase can be added to fresh milk to pre-digest the lactose. This makes lactose-free milk, which is suitable for people who do not produce enough lactase of their own. A student investigated the effect of changing ph and temperature on the digestion of lactose in milk. The results are shown in Tables and 2. Table Effect of ph Table 2 Effect of temperature ph Time taken to digest lactose in minutes Temperature in C Time taken to digest lactose in minutes No digestion (a) The label on a carton of lactose-free milk states: Lactase is normally produced in the stomach of mammals. The results in Table suggest that this statement is not true. Explain how (2) Page 3 of 59

32 (b) Explain, as fully as you can, the results shown in Table (3) (c) Bile is produced in the liver and is released into the small intestine. Bile helps the digestion of lipid in the milk. Describe how (2) (Total 7 marks) Page 32 of 59

33 6 The human body is organised to carry out many different functions. (a) Use words from the box to complete Figure by putting the parts of the body in order of size from smallest to largest. The smallest one has been done for you. (2) (b) The stomach is made of different types of tissue. Draw one line from each type of stomach tissue to the correct description. (3) Page 33 of 59

34 (c) Animals can react to their surroundings because they have nervous systems. A student investigated the behaviour of small animals called woodlice. The student set up the investigation as shown in Figure 2. The student covered one half of a Petri dish with black paper to make that side of the Petri dish dark. The other side had no cover. The student put five woodlice into each side of the dish and then put the clear Petri dish lid back on the dish. Figure 2 After 30 minutes, all the woodlice had moved to the dark side of the Petri dish. Page 34 of 59

35 (i) In this investigation, what is the stimulus that the woodlice responded to? () In this investigation, what is the response that the woodlice made? () (iii) The student concluded that woodlice prefer dark conditions. Give two ways in which the student could improve the investigation to be sure that his conclusion was correct (2) (Total 9 marks) 7 The photograph shows a fossil of a prehistoric bird called Archaeopteryx. By Ghedoghedo (own work) [CC-BY-SA-3.0 ( or GFDL ( /fdl.html)], via Wikimedia Commons; By Steenbergs from Ripon, United Kingdom (Small Fishing Boat In North Sea) [CC-BY-2.0 ( via Wikimedia Commons. Page 35 of 59

36 (a) Describe three ways fossils can be made (3) (b) The drawing shows what an Archaeopteryx might have looked like when it was alive. Scientists think that Archaeopteryx was a predator. Page 36 of 59

37 (i) Look at the drawing. Write down three adaptations that might have helped Archaeopteryx to catch prey. How would each adaptation have helped Archaeopteryx to catch prey? Adaptation... How it helps... Adaptation 2... How it helps... Adaptation 3... How it helps... (3) Archaeopteryx is now extinct. Give two reasons why animals may become extinct (2) (Total 8 marks) Page 37 of 59

38 Mark schemes (a) in sequence: 2 = tissue(s) 3 = organ(s) 4 = system(s) (b) mark for each correct line extra line(s) from one tissue cancel 3 [4] 2 (a) (i) A = (cell) membrane B = cytoplasm do not accept cytoplast To control the activities of the cell Page 38 of 59

39 (b) extra lines cancel 3 [6] 3 (a) Structure Organ Organ system Tissue Stomach Cells lining the stomach Mouth, oesophagus, stomach, liver, pancreas, small and large intestine all 3 correct = 2 marks 2 correct = mark or 0 correct = 0 marks (b) (i) diffusion allow phonetic spelling 2 glucose (iii) mitochondria [5] 4 (a) (i) capillary Page 39 of 59

40 diffusion (b) (i) Z ignore any names large / increased surface / area allow all food absorbed or to absorb more food or improved diffusion [4] 5 (a) (i) A (iii) hydrochloric (acid) / HCl alkali / suitable named example accept sodium hydrogen carbonate / sodium bicarbonate / milk of magnesia / other brand names allow bile (salts) ignore antacid (b) amylase breaks down starch (broken down) into sugars / glucose digestion of starch in the mouth (also) starch broken down in small intestine amylase produced in salivary glands / small intestine / pancreas (c) small intestine allow ileum / duodenum do not accept large intestine [9] 6 (a) (i) muscular Page 40 of 59

41 7 (iii) an electrical device (b) (i) in sequence: (c) (i) prevent backflow (of blood) / allow flow in only one direction / in the correct direction A no mark, but max 2 marks if incorrect 2 / atrium contracts / pressure in 2 increases blood pushes ball (down / towards ventricle / towards 5 ) allow this point even if valve in wrong part of heart (opens valve which) allows blood into 5 / ventricle or converse points re closing the valve (d) (i) involvement of platelets / eg platelets trigger clotting process / release enzyme(s) / release clotting factors fibrinogen to fibrin or meshwork formed (which traps blood cells) Page 4 of 59

42 any four from: to gain 4 marks candidates should include at least: one advantage and one disadvantage Advantages (improved circulation / O 2 supply) provides: more cell respiration more energy released (more) active life / not so tired / more physical activity Disadvantages danger of surgery / operation infection from surgery / operation valve may need replacing clots may form and block blood vessels may need to take anti-coagulants eg warfarin clots may cause heart attacks / strokes 4 [7] 7 (a) (i) tissue extra box ticked cancels the mark organ extra ring drawn cancels the mark (b) (i) Layer B Layer C each extra box ticked cancels mark (contain) chloroplasts / chlorophyll other parts disqualify Page 42 of 59

43 (c) two correct = 2 marks one correct = mark extra line from a part of a cell cancels the mark 2 [7] 8 (a) xylem and phloem either order allow words ringed in box allow mis-spelling if unambiguous (b) (i) movement / spreading out of particles / molecules / ions / atoms ignore names of substances / gases from high to low concentration accept down concentration gradient ignore along / across gradient ignore with gradient oxygen / water (vapour) allow O 2 / O2 ignore O 2 / O allow H 2 O / H2O ignore H 2 O [4] Page 43 of 59

44 9 (a) (i) xylem water minerals / ions / named example(s) ignore nutrients (b) (i) movement of (dissolved) sugar allow additional substances, eg amino acids / correct named sugar (allow sucrose / glucose) allow nutrients / substances / food molecules if sufficiently qualified ignore food alone sugars are made in the leaves so they need to be moved to other parts of the plant for respiration / growth / storage (c) (i) mitochondria for movement of minerals / ions Do not accept water against their concentration gradient [9] 0 (a) (i) A slide B coverslip C (teat / bulb) pipette D (mounted) needle place epidermis on (centre of) slide use pipette to add drop of liquid/ water / stain to epidermis use needle to lower coverslip onto liquid Page 44 of 59

45 (b) (i) 8 4 = 4.5 correct answer with or without working gains 2 marks ( 0.000) 4.5 = correct answer with or without working gains 2 marks allow ecf from part (b)(i) (iii) (eg 4 / 5 / 6) (c) (i) X correct answer with or without working gains 2 marks allow answers in range inclusive because it has the low(est) number of stomata or no stomata on upper surface or only 800 (on lower surface) which means there will be less transpiration / evaporation / water loss via stomata it reduces amount of water (vapour) or reduces transpiration (from upper surface) because lower surface is cooler or in the shade or covered by (folded) wilted leaf [8] (a) (i) nucleus diffusion Page 45 of 59

46 (b) increases / larger surface area (for diffusion) ignore large surface area to volume ratio (c) (i) sugar / glucose accept amino acids / other named monosaccharides (iii) against a concentration gradient or from low to high concentration (active transport requires) energy (from) respiration (d) minerals / ions accept named ion ignore nutrients do not accept water [8] 2 (a) (i) chloroplast cell wall (b) (i) osmosis accept diffusion cell wall (prevents bursting) (c) (i) carbon dioxide allow correct formula glucose allow sugar / starch any two from: (d) light sensitive spot detects light tells flagellum to move towards light more light = more photosynthesis (cell has) larger SA:volume ratio 2 Page 46 of 59

47 short (diffusion) distance allow correct description (diffusion) via cell membrane is sufficient / good enough or flow of water maintains concentration gradient [] 3 (a) pancreas apply list principle (b) (i) protein apply list principle any one from: (controlling / changing) diet accept sugar(y foods) / named eg ignore references to starch / fat / protein / fibre exercise accept example, eg go for a run (c) (i) increase pancreas transplant then fall accept named drug eg metformin ignore reference to women relevant data quote (for male) eg max at ages or starts at 0 (per thousand) or max at 30 (per thousand) or ends at 20 (per thousand) accept a difference between any pairs of numbers in data set accept quotes from scale eg 30 or 30 per thousand but not 30 thousand ; to within accuracy of +/- 2 (per thousand) (between 0 and 64) more females (than males) or less males (than females) ignore numbers allow eg females more diabetic than males Page 47 of 59

48 do not allow incorrect formula e.g. H 2 Cl / HCl 2 (over 65) more males (than females) or less females (than males) allow eg males more diabetic than females [8] 4 (a) (i) amino acid(s) accept peptide(s) do not allow polypeptide(s) protease (b) (i) 2 (iii) repeat do not allow other enzyme / substrate using smaller ph intervals between ph and ph3 allow smaller intervals on both sides of / around ph2 allow smaller intervals on both sides of / around answer to (b)(i) enzyme / pepsin denatured / shape changed do not allow enzyme killed allow enzyme destroyed enzyme / pepsin no longer fits (substrate) allow enzyme / pepsin does not work (c) hydrochloric (acid) allow phonetic spelling accept HCl allow HCL ignore hcl [8] 5 (a) stomach is acidic / has low ph allow any ph below 7 ignore stomach is not alkaline Page 48 of 59

49 lactase works best / well in alkali / high ph / neutral / non-acidic conditions allow any ph of 7 and above accept works slowly in acid conditions allow figures from table with a comparison ignore reference to temperature (b) any three from: (below 40( C)) increase in temperature increases rate / speed of reaction reference to molecules moving faster / colliding faster / harder / more collisions enzyme optimum / works best at 40 C allow value(s) in range ignore body temperature unless qualified high temperatures (above 40 C) / 45 C / 50 C enzyme denatured allow synonyms for denaturation, but do not allow killed denaturation at high and low temperature does not gain this mark ignore references to time / ph 3 (c) any two from: acid neutralised or conditions made neutral / alkali accept bile is alkaline (allow) emulsification / greater surface area (of lipid / fat) allow description of emulsification eg fat broken down / broken up into droplets do not accept idea of chemical breakdown lipase / enzymes (in small intestine) work more effectively / better allow better for enzymes ignore reference to other named enzymes 2 [7] 6 (a) tissue organ organ system one right for mark three right for 2 marks 2 Page 49 of 59

50 (b) Epithelial tissue covers the outside and the inside of the stomach more than one line from a tissue = no mark Glandular tissue produces digestive juices Muscular tissue allows food to be churned around the stomach (c) (i) light ignore dark (iii) moving (to the dark) any two from: use more woodlice repeat the experiment run for a longer time 2 [9] 7 (a) any three from: parts of organisms have not decayed accept in amber / resin allow bones are preserved conditions needed for decay are absent accept appropriate examples, eg acidic in bogs / lack of oxygen parts of the organism are replaced by other materials as they decay accept mineralised or other preserved traces of organisms, eg footprints, burrows and rootlet traces allow imprint or marking of organism 3 (b) (i) teeth for biting (prey) must give structure + explanation claws to grip (prey) accept sensible uses wing / tail for flight to find (prey) Page 50 of 59

51 any two from: new predators new diseases better competitors catastrophe eg volcanic eruption, meteor changes to environment over geological time accept climate change allow change in weather prey dies out or lack of food allow hunted to extinction 2 [8] Page 5 of 59

52 Examiner reports (a) (b) Almost half of the students were able to list tissues-organs-systems in the correct size order. The distracters in this section proved very distracting and less than half the students could assign the correct function to all three types of tissue muscular, glandular and epithelial. 2 This question was well answered by most students. (a) (i) Most knew that structure A in the diagram of cells from the stomach lining was the cell membrane and that B was the cytoplasm, although a few got these the wrong way round. Nearly all students knew that the function of the nucleus was to control the activities of the cell. 3 (b) (a) Over three quarters of students were able to assign the three parts of the body to their scientific name. Over three quarters of students knew that the stomach was an organ, that the cells lining it made up a tissue, and that the mouth, oesophagus, stomach, liver, pancreas, small and large intestine constituted an organ system. (b) (i) Just over half the students recognised that the process of diffusion had been defined in the question as the process by which oxygen moves from the blood to the cells lining the stomach, although some suggested respiration and others photosynthesis. (iii) The vast majority selected glucose as the other substance that would also need to be supplied for use in respiration. Most students knew that the mitochondria were used for aerobic respiration, although the cell membrane and the nucleus distracted a few in equal proportion. 4 This question was well answered by most students. (a) Most knew that structure A in the diagram of the villus was a capillary and that the villi absorbed the products of digestion by diffusion. (b) Similarly, most were able to identify region Z (the small intestine) on the diagram of the digestive system as the part where most villi were found. Just under half of the students knew that the purpose of having large numbers of villi was to increase the surface area or to allow more food to be absorbed. Some clearly confused the situation with gas exchange and wrote about the absorption of oxygen. Page 52 of 59

53 5 (a) The vast majority were able to identify structure A on the diagram as the stomach. Less than one-fifth knew that the acid produced by the stomach was hydrochloric acid. (iii) More students knew that some sort of alkali would need to be present in a medicine that would neutralise excess stomach acid. (b) (c) Most answers to this question were very poor, with half of the students scoring no marks at all for their accounts of carbohydrate digestion, despite being given the words amylase, starch and sugars for guidance. Many did not seem to know that starch was a carbohydrate or that starch was made of sugar molecules joined together. The site of amylase production and the site of its action were not always distinguished digestion of starch does not occur in the pancreas or in the salivary glands as some students inferred. Some also wasted time by writing about topics irrelevant to the question, such as absorption and defaecation. Just over one-quarter of students knew that the site of absorption of the products of digestion was the small intestine. Page 53 of 59

54 6 (a) (b) (c) These parts were made up of five multiple-choice questions based upon a diagram of a section through the human heart. Nearly all students knew that the heart wall was composed mainly of muscular tissue, but only half knew the location of the pacemaker, although the fact that the latter was an electrical device (rather than a pump or a valve) was again well known. The majority also knew which chambers of the heart pumped out oxygenated blood and received either deoxygenated blood or oxygenated blood, and which valve would close when the blood pressure in the aorta exceeded that in the left ventricle. These parts were made up of five multiple-choice questions based upon a diagram of a section through the human heart. Nearly all students knew that the heart wall was composed mainly of muscular tissue, but only half knew the location of the pacemaker, although the fact that the latter was an electrical device (rather than a pump or a valve) was again well known. The majority also knew which chambers of the heart pumped out oxygenated blood and received either deoxygenated blood or oxygenated blood, and which valve would close when the blood pressure in the aorta exceeded that in the left ventricle. This section introduced the concept of an artificial replacement valve. Most knew that valves prevent the backflow of blood or ensure that the blood flows in only one direction. Only the more able students were successful in part, being able to work out how the pressure of the blood would alter the position of the ball in the valve and thus allow blood to pass only from the atrium to the ventricle. Very few students mentioned contraction of the atrium as a means of generating pressure. (d) (i) Students had some extraordinary ideas about the nature of blood clotting, many evidently confusing it with the antigen-antibody interaction which was the subject of a question in the January 204 paper. About one-quarter of the students were able to invoke both the involvement of platelets and the conversion of fibrinogen into fibrin fibres. This question included some information about the dangers of blood clot formation on an artificial heart valve. Using this information students had to evaluate the advantages and disadvantages of such valves. For about one-third of the students, this was an invitation to copy out most of the given passage rather than to use it as a source of information for developing their own argument such students scored zero marks. Given that the replacement valve can dramatically improve the blood circulation and supply of oxygen to the body s tissues, students were expected to point out that this would improve cell respiration, releasing more energy for physical activity (these points alone would have scored three out of the four marks available for this question). And, given that blood clots can form on (the valve s) surface then break away and be carried around the body by the blood, it was hoped that students would realise the consequences of this in terms of blockage of blood vessels followed by perhaps a heart attack or stroke. Very few students were able to make more than one or two valid points. Being an evaluation question, students were expected to include both advantages and disadvantages in their answers. Page 54 of 59

55 7 (a) The concept of organisation, as in part (a), has not been directly examined for several sessions and it was clear that many candidates had not included this in their preparation, as answers here often showed a disappointing lack of understanding. (i) The correct answer, tissue, was selected by only just over half the candidates, with cell coming a very close second. By far the greatest number of candidates chose the incorrect organism. This is particularly surprising for examiners, who expect that the term organism is one that candidates will encounter frequently in their work. (b) (c) However, there were more pleasing attempts in part (b) Many candidates selected the correct two layers, B and C and then went on to explain their selections with appropriate reasons, referring to chloroplasts or chlorophyll. Those who selected A and D in part (b)(i) usually gave a logical, if incorrect reason for their choice, usually that these two layers were on the outside so would be most exposed to light. Despite there being a general improvement in candidates following instructions, in questions such as this, around 6% did not tick just two boxes despite the required number being emboldened twice, along with the mark allocation providing further evidence as to how many boxes should be ticked. Those who gave reasons which did not exclusively refer to chloroplasts / chlorophyll were not credited. Thus answers such as the cells in these layers have chloroplasts and a nucleus provided a list for the examiners to choose from. In such circumstances the examiners are instructed not to make a choice, whichever order the components of the list should be in, and thus not award the mark. A high proportion of candidates scored both marks, with most of the rest gaining one mark, the most common problem for candidates being the decision as to what the nucleus controls. 8 This was the first of three standard demand questions common to both the Foundation and Higher Tier papers. (a) (b) A little less than half of students recognised the terms xylem and phloem as the names of the two tissues in the leaf that are used for transport. Just over a quarter of the students were able to give a satisfactory definition of diffusion. Although many knew that a substance would move from high to low concentration by diffusion, far fewer stressed that it was molecules / particles of the substance that moved. in part, most answers were either oxygen or carbon dioxide, less than half of the students correctly gave the former as the gas that would diffuse out of the leaf on a sunny day. Page 55 of 59

56 9 (a) (i) Almost all students were able to correctly identify xylem labelled on the diagram. About two-thirds of the students knew that both water and minerals were transported in the xylem. Of those who scored one mark, water was the most common response. Many students incorrectly wrote sugars or nutrients. (b) (i) Just over half of the students could define translocation. Many students mentioned water only being transported in phloem. Very few students gained both marks to explain why translocation is important. The crux of the question lay in recognising that sugars are made in the leaves but need to be moved to other parts of the plant for respiration or growth. (c) (i) Almost all students could identify mitochondria as the cell part releasing energy. This was a high demand item and only about one-third of students scored two marks and one-third one mark only. One mark was awarded if substances or nutrients were mentioned as being moved against the concentration gradient since this term could include minerals or ions. Some students wrote water is moved against the concentration gradient and although the latter part is true for minerals, in the wrong context (water) no marks could be awarded. (a) (i) The majority of students correctly identified the nucleus in the epithelial cell. Nearly all of the students knew that soluble food molecules were absorbed by diffusion. Osmosis was the most common incorrect answer. (b) A highly folded cell surface increases the surface area of a cell. Many students lost a mark in this question for failing to use comparative wording, hence a large surface area did not gain a mark, whereas a larger surface area did. Some students referred to the surface area to volume ratio which was not relevant. (c) (i) Over half of students know one food molecule absorbed by active transport. Glucose and amino acids were the most common answers. Other correctly named monosaccharides were accepted but protein was not allowed. (iii) Just over half the cohort were able to state why some food molecules area absorbed by active transport. Students most commonly said that absorption was against the concentration gradient. Some students elaborated in more detail to state that there was a higher concentration of molecules in the cell or blood compared to the gut. Fewer than half the students correctly described that energy released from respiration is required for active transport. Many students lost at least one mark by saying that respiration produces or makes or creates energy. Energy may only be released or transferred or provided by respiration. (d) Only two thirds of the cohort was able to state one substance that plants absorb by active transport. The most common answer was mineral ions but many also named an ion, most commonly nitrates. The most common incorrect responses were water, nutrients, nitrogen, pollen, oxygen and proteins. Page 56 of 59

57 2 (a) (i) The majority of students were able to correctly identify the chloroplast and cell wall. The majority of students were able to correctly identify the chloroplast and cell wall. (b) (i) Almost all students were able to name osmosis (or diffusion) as the process by which water moves into the cell. About two-thirds of the students answered correctly with explicit reference to how the cell wall prevents the algae from bursting. If an incorrect reason was given, the mark was not awarded, eg the cell wall controls how much water enters and leaves the cell, the cell wall is thin making diffusion easy. Some common incorrect answers included; it is isotonic ; the vacuole ; the cell is turgid ; the cell wall is partially permeable. (c) (i) Almost all students were able to complete the word equation for photosynthesis with correct formulae accepted. The majority of students were awarded the maximum of two marks for this question to suggest how the light-sensitive spot and flagellum could work to increase photosynthesis. In fact, many responses included all of the three available marking points. Credit was given where students had interpreted the information differently to say that the light-sensitive spot detects when the cell is dark and so the flagella move the cell to a lighter position. Some incorrect responses included: light sensitive spot sees the light, flagellum would catch the light, flagellum have a large surface area to catch the light and flagellum detect levels of carbon dioxide needed for photosynthesis. (d) Very few students scored full marks in this question. Again, students found it difficult to express their ideas and knowledge in this high demand area of the specification. 3 (a) The most common correct answer was marking point (larger SA:volume ratio), followed by marking point 2 (short diffusion distance). Where students gained two marks, both of the first two marking points were linked. Some students were not awarded marking point because they just wrote large surface area with no reference to volume. Many students missed out on the third marking point because they referred to the cell wall as opposed to the cell membrane. Some other incorrect responses included: gas exchange is easier in water than air single celled organisms use their cell walls for gas exchange diffusion is easy because they are small they don't need a lot of oxygen because they are small not enough space inside their cell for complex structures they don't have a respiratory system because they photosynthesise thin walls so gas can diffuse easily. The pancreas as the site of insulin production was well known by the overwhelming majority of students. However students were not secure in their understanding that proteins are digested in the stomach, thus insulin must be a protein, this piece of deduction requiring two steps. Many students here selected carbohydrate perhaps because of the link between insulin and blood glucose concentrations described in the question stem. Page 57 of 59

58 (b) Exercise, eating less sugar or simply control through the diet were commonly given although a surprisingly high number of students believed that additional dietary sugar would be helpful. (c) (i) Students often appeared to forget which part of the chart they should be describing, as there were many descriptions of the changes in females and comparisons between males and females at the various ages. Some students merely referred to the start and end points, ignoring the reduction after the ages of An appropriate reference to the data was expected for the third mark and students could attain this in a wide variety of ways. Most chose to quote either start or end values, others deduced the change from start to end, or quoted the peak value. All of these were acceptable, however incorrect reading of the scale on the y-axis was not accepted, thus suggestions such as diabetic males at years, rather than 30 per 000, were not credited. Just a few (appropriate) words would have secured the marks for both parts. Students often went into unnecessary detailed descriptions and even explanations. However, the majority of students did identify the relevant differences. 4 (a) (i) Less than one-third of students knew that amino acids (or, alternatively, peptides) were the product of protein digestion. There was much more success in selecting protease as the name of the proteindigesting enzyme. (b) (i) Almost two-thirds of students were able to select ph 2 from the table of data as the ph at which the enzyme worked best, although a significant minority chose a value between 5 and 7 (the table showed that no reaction had taken place at these values, whereas ph 2 had the greatest decrease in length of the egg white). (iii) Most students appreciated that the experiment would need to be repeated; however, this would not have improved the accuracy, as demanded by the question. Very few students were able to qualify their answer with a suitable ph range around their answer for (i), and at smaller intervals of ph. While a few students knew that denaturation of the enzyme would be the likely reason for it not working at ph 5 to 7, many thought that digestion of the protein was brought about by acid and argued that, since the solution was less acidic, digestion would cease. The most common mark awarded was for the idea that the enzyme did not work at these phs. 5 (c) (a) Just over one-third of students knew that hydrochloric acid was responsible for the low ph in the stomach. Incorrect answers included bile and amino acid. Many students were able to explain that the contents of the stomach are acidic and that the evidence in Table showed lactase was more active in alkaline conditions. Others only got halfway to this, giving either one side or the other of this explanation. However a considerable number of students appeared to have little understanding of the ph scale, suggesting that high ph means acid conditions. These students then struggled to gain any marks here. Page 58 of 59

59 6 (b) (c) (a) (b) Students often failed to refer to the rate of enzyme activity; choosing to describe the results in Table 2, rather than to explain them as demanded by the question. This usually left them with no marks, despite having filled the available space. Those students who did attempt explanations often omitted to refer to temperatures below the optimum, thus limiting their maximum mark to two. Denaturation was a commonly known term, although some believed that this happens at both high and low temperatures. There were very few references to enzymes being killed. Optimum, along with an appropriate temperature was also commonly accepted. Only the neutralising effect of bile is described in the specification. Examiners also accepted emulsification or a description of this process. The advantage of both these processes is the same, intestinal enzymes work better / faster. Students were sometimes confused as to where bile was added to food, often describing neutralisation as being in the stomach, rather than occurring after the food had left the stomach. References to helping lactase work faster may be true, but were not accepted as the question asked about the digestion of lipid. The knowledge of bile, its composition and effects was surprisingly sparse. Many believed that it contains enzymes or is an acid or that it simply breaks down fats and as a result marks for this final part were below what the examiners had hoped. This general marked question was a straightforward start to the paper with nearly all students answering correctly. Students had to complete the order of tissue, organ and organ system. A few students completed the boxes in reverse, which gained one mark since tissue was then still in the correct position. More students than expected did not match all the tissue types to the correct descriptions. (c) (i) Students were asked to state the stimulus in the investigation. Generally this question was well answered with few mistakes. Most students gave "light" as the answer, or acceptable derivatives of thereof. Some incorrect answers included: darkness, colour of paper and black paper. (iii) Students were asked to state the response of the woodlice. Again, a generally well answered question with the majority of students responding correctly. Some common incorrect answers included: muscular contractions, without any reference to movement, attracted to the dark side and phototropism. This question assessed the AO3 skill of method improvement. Around half of students scored the full two marks on this question. The most common correct answers came from the first two marking points in the mark scheme. Almost half of the students gained one mark. Page 59 of 59