MARKING SCHEME - HALF-YEARLY EXAMS 2017/2018

Transcription

1 S E C O N D A R Y S C H O O L M R I E H E L ST THOMAS MORE COLLEGE SECONDARY SCHOOL ZEJTUN MARKING SCHEME - HALF-YEARLY EXAMS 2017/2018 YEAR 10 Biology Time: 2hrs NOTE: / indicates alternative answers. Answers are an indication of what is acceptable. Accept other correct answers not indicated below after checking with other examiners. Section A: Answer ALL the questions in this section in the space provided. This section carries a total of 55 marks. 1. A balanced diet is one that gives your body the nutrients it needs to function correctly. a) Some of the nutrients included in a balanced diet are fat, fibre, mineral salts and vitamins. Name two other energy-releasing nutrients that should be part of a balanced diet. Carbohydrates and Proteins. b) Complete the table to show how each of the listed types of diet would affect the human body. Type of Diet Low vitamin D content High fat content Low iron content Effect on Human Body Lack of Calcium absorption / weak bones / rickets? Fat deposits under skin / obesity Anaemia / Lack of red blood cells (3) c) Calcium is a type of mineral salt present in all diets. i) What is the main role of calcium in the human body? For building bones & teeth / makes bones strong or hard / strong bones Biology Y10 HY Page 1 of 13

2 ii) Name the deficiency disease that results from lack of calcium in the diet. Rickets iii) Name a food item that helps to increase the calcium levels in our body. Milk / Cheese / leafy greens / nuts / small fishes with edible bones d) Many of the processes within your body depend on water, so it is important that you get enough of this essential nutrient in your diet. Write down two functions of water in the human body. Reactant / Reaction medium / Transport medium / Temperature regulation (Any 2 1 mark each) Total: 10 marks 2. Some people make use of diet supplements to lose weight. The diet supplements should include all the necessary nutrients normally present in a healthy diet. A group of Biology students investigated the nutrient content in a type of diet supplement. They carried out a number of food tests using the supplement, and recorded the results in the table below: Tested for Reagent(s) Used Colour of Mixture Before After Result Glucose Benedict s solution Blue Brick-red Present Starch Iodine solution Brown Yellowish brown Absent Protein Copper Sulphate and Sodium hydroxide (conc) Blue Purple Present a) Complete the table by writing the correct word(s) in each empty box. (½ mark each = 4) b) Write down the method the biology students used to carry out the test for glucose. Add a few drops of Benedict s solution to the food sample Heat in a water bath Biology Y10 HY Page 2 of 13

3 c) Glucose and starch are both carbohydrates. Write down two differences between these molecules. Soluble - insoluble / monosaccharide polysaccharide / simple sugar - complex sugar / sweet not sweet or tasteless (Any 2) d) Carbohydrates are used to build organic molecules. Explain. Glucose + nitrate Amino acids / proteins Total: 10 marks 3. A large fish, known as a pike, was caught from a lake. When it was opened, its stomach had many small fish known as roach. The roach feeds on the lake plants. a) Use the information above to draw a food chain of the mentioned organisms. Lake plants Roach Pike b) Draw and label a pyramid of biomass of these organisms. Pike Roach Lake plants c) Write the name of the organism that occupies the first trophic level. Lake plants d) The pike s stomach had already started digesting the small fish. Describe the process that occurs in the pike s stomach to digest the protein found in the small fish. Gastric juice is secreted / Contain HCl and pepsin/protease Pepsin breaks down proteins into polypeptides HCl provides acidic ph for pepsin (3) Biology Y10 HY Page 3 of 13

4 e) Further investigation of the pike s stomach revealed the presence of mucus. List one function of mucus within the stomach. Protects inner lining against acid / self-digestion by pepsin (Any 1) f) Explain how catching too many pike would affect the lake ecosystem. Less pike = more roaches = less lake plants Total:11 marks 4. The following diagram shows a few organisms present in a particular ecosystem. eagle hawk crow finch locust aphid grass tree a) Finches are also part of this ecosystem. Finches feed on the seeds produced by the tree, and are eaten by the hawks and eagles. Add this information to the food web above. (1 mark for each correct link = 3) b) Suggest two changes that might happen if all the eagles in this ecosystem died out. Change 1: More hawks = less crows Change 2: More finches = increased competition for seeds Biology Y10 HY Page 4 of 13

5 c) Match the type of organism to its correct definition. Two of the definitions are extra. Type of organism present in ecosystem Definition carnivore An animal that obtains its energy from eating other animals The position of an organism within the food web consumer An animal that obtains its energy from eating other plants decomposer An animal that obtains its energy from eating other organisms An animal that obtains its energy from dead or waste organic matter Herbivore An organism that makes its own organic nutrients (1 mark each = 4) Total: 9 marks 5. Bile is a dark green to yellowish brown fluid, produced by the liver of most vertebrates, which aids the digestion of lipids in the small intestine. a) In which structure is bile stored? Gall bladder b) Bile aids the digestion of lipids. Explain this biological statement. It breaks down large lipid droplets into smaller ones This increases surface area for digestion Emulsification (3) Biology Y10 HY Page 5 of 13

6 c) The following diagram shows the apparatus set at the start of an experiment that investigated the digestion of fat by an enzyme A. The apparatus is kept in a water bath at 40 C, for 30 minutes, during which the colour changes of the ph indicator are observed. The ph indicator changes colour as follows: ph value Below 7 Indicator colour Red 7 Green Above 7 Blue i) State the name of enzyme A. Lipase ii) Explain why the apparatus is kept in a water bath at 40 C. Optimum temperature / Close to body temperature (Any 1) iii) From the table above, suggest the colour which would be observed after 30 minutes. Give a reason for your answer. Red Lipids broken down into glycerol and fatty acids Fatty acids have an acidic ph - below 7 (3) Total: 9 marks Biology Y10 HY Page 6 of 13

7 6. The following diagram shows the villus (pl.villi). This structure is found in the ileum, which forms part of the small intestine. A B a) What is the main function of the villi in the ileum? Absorption of nutrients b) State two ways of how villi are adapted to perform their function. Large surface area / Network of blood vessels / Lacteal and Lymph ducts / Thin epithelium (Any 2) c) Name two substances which are normally absorbed into part A. Fatty acids and glycerol d) To which organ does the blood vessel B lead to? Liver e) Coeliac disease is a disease caused by intolerance to gluten, a chemical usually found in products such as wheat and oat. This intolerance is thought to cause damage to the villi. Suggest one effect of this disease. Less absorption / abdominal pain / weight loss (Any 1 or equivalent) Total: 6 marks Biology Y10 HY Page 7 of 13

8 Volume of juice obtained using 80% Section B: Answer question ONE and ANY OTHER TWO questions on the papers provided. This section carries a total of 45 marks. 1. Pectinase is an enzyme that breaks down pectin, a polysaccharide found in plant cell walls. Pectinase enzymes are commonly used in industrial processes involving the breakdown of plant materials, such as the extraction of fruit juice from fruit. Biology students investigated the effect of using different concentrations of pectinase on apples, by measuring the volume of apple juice obtained. The following table shows the results obtained: Time/hours Volume of juice obtained using 40% pectinase concentration/cm 3 Volume of juice obtained using 80% pectinase concentration/cm a) Plot a graph of the volume of juice collected at 80% pectinase concentration (y-axis) against the time (x-axis) (4) Volume of juice obtained using 80% pectinase concentration (cm 3 ) against time (hours) pectinase concentration/cm Time/hours Correct plotting Correct use of scales / graph Title Labels Deduct ½ mark if units are not included. Deduct 1 mark if both sets of data are plotted. Biology Y10 HY Page 8 of 13

9 b) Using the table of results, write down a suitable conclusion to clearly show the difference between 40% and 80% pectinase concentration. A higher concentration of enzyme results in a larger amount of juice / More juice is produced when 80% pectinase is used (Or equivalent) c) Throughout the experiment, the temperature was kept constant. Explain why. A change in temperature affects rate of reaction / Effect of temperature is not being investigated (Or equivalent = 1 mark) Only one factor should be changed at a time (1 mark) d) Write down one other factor that should have been kept constant throughout the experiment. The mass of apple used / Volume of enzyme solution used / Same apple / Same ph (Any 1) e) One of the students commented that fruit juice would still be extracted if the enzyme cellulase was used instead of pectinase. i) Is the student correct? ii) Give a reason for your answer. Yes. Cellulase breaks down cellulose present in the cell wall. f) Enzymes are commonly used in industrial processes. Write down three reasons why enzymes are normally included in industrial processes. (3) They are cheap / Do not need high temperatures to work / Less expensive to energy saving / Can be re-used / Only small amounts needed (Any 3) g) Besides extracting fruit juice, give one other example of enzyme use in industry. Biological washing powder / Fermentation / Breaking down blood clots / Making of chocolates or syrups / Making meat tender / Removing hair from animal skins / Skinning fish / Removing seed coats from cereal grains (Any 1 or equivalent) Total: 15 marks Biology Y10 HY Page 9 of 13

10 2. Green plants make their own food. They use simple substances from the air & soil, and build them into complex materials. This process is known as photosynthesis. a) Name one type of plant cell that performs photosynthesis and state where it can be found. Palisade mesophyll cell / Spongy mesophyll cell / guard cells (Any 1) Found in the leaf b) Name a plant cell that does not perform photosynthesis. Epidermal cell / Root cell (Any 1) c) Explain how each of the following helps a leaf to photosynthesise: i) There is an air space behind each stoma. ii) Leaves have a large surface area. iii) The veins in a leaf branch repeatedly. Air space allow gases to diffuse in and out / efficient gaseous exchange A large surface area allows leaf to absorb more light Veins bring water to the cells d) Two substances plants take up from the soil are magnesium and nitrogen (in the form of nitrates). For each of these minerals, state its function in plants, and the deficiency effect. (4) Mg: Part of chlorophyll molecule / helps activate growth enzymes Deficiency: Yellowing between leaf veins / Yellowing around leaf margins / Leaf death (Any 1) N: Synthesis of proteins and other complex chemicals Deficiency: Plants are stunted and yellow / No new shoots / Delayed flowering / reduced seed formation (Any 1) e) A limiting factor is something present in the environment in such short supplies that it restricts processes such as photosynthesis. List one limiting factor that might limit the rate of photosynthesis in the following situations: i) a plant growing on the forest floor; ii) a plant on a very hot, dry day. i) Amount of light ii) Amount of water / Temperature (Any 1) f) Although the setting up of greenhouses is very expensive, farmers still prefer to grow their plants and crops in greenhouses. Explain this statement. (3) Crops can be grown out of season / Can grow non-local species / Protection against weather / Control of factors for optimal growth / Cross pollination can be carried out manually as very little insects enter the greenhouse / Biological pest control is easier (Any 3) Total: 15 marks Biology Y10 HY Page 10 of 13

11 3. Explain each of the following biological statements: a) School canteens are encouraged to sell unsweetened cereals and fruit rather than sweets and chocolates. Sweets and chocolates have large amount of sugar Can cause damage to teeth / Diabetes / Obesity b) A nutritionist suggested to a vegetarian to include Soya beans in the diet. (3) Vegetarians do not eat meat Lack of protein Soya beans are rich in protein c) Food chains normally do not have more than 5 trophic levels. (3) 90% energy lost/used at each trophic level Only 10% is passed on Top organisms do not get enough energy to survive d) One of the secretions of the pancreas is sodium bicarbonate. Neutralises the acidity of chyme Provides the correct ph for pancreatic and intestinal enzymes e) The liver is considered to be a storage organ. (3) Stores food substances like glycogen, fat-soluble vitamins and iron f) Decomposers have an important role in all ecosystems. Break down remains of dead organisms / Cause decay / break down remains into simple chemical substance (Any 1) Responsible for recycling of nutrients from higher to lower trophic levels Total: 15 marks Biology Y10 HY Page 11 of 13

12 4. This question is about the human gut and the process of digestion. a) Digestion starts in the mouth. List: i) one mechanical (physical) way ii) and one chemical way in which digestion in the mouth takes place. Teeth chop and crush food Salivary amylase breaks down starch into maltose b) Explain how food reaches the stomach from the mouth. Waves of muscular contractions in wall of gullet push bolus down This is called peristalsis c) Name a region in the human gut with a: i) low ph ii) ph greater than 7 Low ph: Stomach High ph: Duodenum / ileum (Any 1) d) The mammalian body is capable of storing excess carbohydrates, but it cannot store excess proteins. i) Name the sugar that excess carbohydrates are stored as. ii) Name the organ in which excess carbohydrates are normally stored. iii) Explain how the mammalian body deals with extra proteins i) Glycogen ii) Liver iii) Deamination Amine group is removed from amino acid Remaining part is stored as a carbohydrate e) i) Explain the effect of a diet low in fibre. ii) Suggest one type of food that increases intake of fibre. i) Constipation / lack of bulk results in difficulty in pushing out faeces ii) Cereal grains / Bread / Vegetables (Any 1 or equivalent) (3) Total: 15 marks Biology Y10 HY Page 12 of 13

13 5. Many different species of ruminant animals are found around the world. Ruminants include cattle, sheep, goats, buffalo, deer, giraffes and camels. These animals all have a digestive system that is uniquely different from our own. a) What is a ruminant? Herbivores with a 4-chambered stomach b) Describe the importance of the following structures in the dentition of a ruminant: i) horny pad; ii) diastema; iii) flat molars and premolars i) Lower incisors act like pincers against it / Used for cropping grass (Any 1) ii) Allows the tongue to manipulate food easily iii) Allow crushing and grinding of food c) Explain why the molars and premolars of herbivores grow continuously throughout their life. d) Ruminants host cellulose-digesting bacteria in their stomach. Explain the importance of these bacteria. (3) Ruminants are not capable of digesting cellulose / No cellulase Bacteria break down cellulose into sugars Sugars can be absorbed by ruminant e) Lions are carnivores. Give three ways of how its dentition is expected to be different from that of a herbivore. (3) Pointed incisors used for nibbling meat from bones Large, pointed canines used for piercing skin and tearing flesh Carnissal teeth scrape flesh off bones with scissor-like action f) Carnivores normally have a large and active liver. Explain Carnivores have diet high in protein Liver is responsible for large amount of deamination g) Lions are referred to as predators. Give two reasons why predation is beneficial to the prey species. Controls number of prey / less competition within prey population Eliminates weak members Total: 15 marks Biology Y10 HY Page 13 of 13