University of Swaziland Department of Inservice Education SGCSE Examinations BIOLOGY 6884 MODEL ANSWERS

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1 PAPER 1 Q1 The figure shows different animals. (i) State the class to which each of the animals belongs. [5] A= Mollusc B=Mammal C=Insect D=Arachnid C=Crustacean Q2. The figure shows a palisade cell. Name the parts labeled F, G, H and I. [2] F=Vacuole/cell sapg=chloroplast;h=nucleus;i=cytoplasm; Q3. Circle the nutrient that is required for the proper growth of the thyroid gland.[1] Calcium, Iron, Iodine, Phosphorus F G H I Q4. Name one food source for each of the following nutrients.[3] (i) Carbohydrates: maize or rice or wheat or potatoes or sorghum or cassava or any other cereal (ii) Proteins: meat or fish or milk or cheese or beans or legumes (iii) Vitamin D: fish liver oil or egg yolk or milk or yeast or butter or dark green vegetables like spinach Q5. Name three substances that must be present in a balanced diet other than carbohydrates, Proteins and vitamins.[3] minerals, roughage, water and fats. (Any 3 of them in any order) Q6. Name a substance that could be lost from blood as it passes through the: (i) kidneys: [1] Water or nitrogenous wastes or urea or salts; (ii) lungs: [1] carbon dioxide or water Q7. Use the following terms to complete statements A, B, C and D below. technology, pollution, eutrophication, déforestation, herbicides, pesticides A. The overuse of fertilizers can result in them being washed into the rivers resulting in an overgrowth of algae. This is calledeutrophication B. Herbicides are chemicals which can be used to destroy weeds and can also be washed into rivers. C. Sewage, chemical waste and poisonous gases are all harmful to the environment. A term used to describe these is pollution; D. Uncontrolled cutting of vegetation can result in deforestation [4] Q8. The figure shows a structure that plays a part in a reflex action. 1

2 State the name of the structure. [1] Sensory neuron Q9. In inheritance the genes are represented by letters. State the name given to the genotype represented by Tt.[1] heterozygous Q10. A 20 year old man is found to be sexually under-developed. Doctors say he produces very little of an essential hormone. Name this essential hormone.[1] testosterone Q11. Some animals are conserved by controlling their population. (a) State one reason why conservation of species is important.[1] to avoid/prevent extinction of endangered species;/aw R Tourism alone (b) Name an example of an animal whose population is controlled by cultural hunting expeditions in Swaziland.[1] Impala (or any other rare herbivore) Q12. Name the two parts that make up the central nervous system.[2] The brain and the spinal cord; Q13. During vigorous exercise the body generates heat that may raise body temperature. Name two changes that will occur in the skin and surface blood vessels to return the body temperature to its original level.[2] 1. Vasodilation 2. sweating Q14. State one difference in composition between inspired and expired air.[1] There is a higher concentration of oxygen in inspired air than in expired air, or There is a lower concentration of carbon dioxide in inspired air than expired air, or There is less moisture in inspired air than in expired. Q15. Genetic engineering is often used to produce better products for commercial purposes. State one example of the use of genetic engineering.[1] crop production or food production or chicken broilers production Q16. An increasing number of people are choosing to use drugs that are illegal. (a) Name two drugs that cause social problems when misused.[2] dagga also called marijuana or cannabis and/or cocaine and/or heroin (b) State one social problem associated with alcohol abuse[1] broken families or poverty Q17. The figure A shows the front view of an eye and B shows the same eye a few minutes later. A What change in the environment brought about the change in the appearance of the eye from A to B? [1] The light was reduced. Less light entered the eye and the pupil widened to allow more light to enter. B 2

3 Q18. The figure shows pyramids constructed from the following food chain. marula trees cutworms birds snakes Excretion, Respiration, Movement (any 2) (ii) State two ways in which plants show sensitivity. [2] Plant roots grow down in response to the pull of gravity, they grow towards water and nutrients; they also grow around objects in response to touch when in contact with an object. Plant shoots grow towards light (b) Study the diagrams of plants below. Pyramid L Pyramid M (a) Name the main source of energy for this food chain.[1] sun (b) A grassland next to trees is a suitable place for snakes to live. State the ecological term used to describe such a place. [1] habitat (c) Identify and name an organism from the food chain which occupies trophic level two. [1] cutworms (d) Which of the pyramids shows a biomass pyramid?[1] pyramid M (e) State what would be most likely to happen to the number of snakes if all the birds were killed.[1] The number of snakes would decrease - PAPER 2 Q1. Sibongile loves playing with her puppy Spotty when she comes back from school. Spotty jumps high to touch Sibongile s chest. Sometimes he urinates while wagging his tail. They both run around the yard until Spotty pants with saliva dropping from his tongue. When Spotty saw Sibongile he displayed a characteristic of living things named as sensitivity. (a) (i) Identify from Spotty s behaviour two other characteristics of living things. [2] Use the key below to identify the plants A, B, C and D. [3] 1. Leaves arise individually from stem go to 2 More than one leaflets arising from petiole go to 3 2. Leaf has parallel veins running from the midrib Amelanchier Sanguinea Leaf has a network of veins Cocculus carolinus 3. Leaflets arise from different points on the petiole Acacia farnesiana Leaflets arise from same point on the petiole Rubus hispidus A. Rubus hispidus; B. Acacia farnesian;; C. Amelachier sanguinea; D. Cocculus carolinus Q2. A pupil set up the apparatus below to investigate the action of the enzyme lipase on peanuts that were ground into powder. Equal amounts of water, bile salts and peanut powder were added into test tube D and test tube E. Enzyme lipase was added to test tube D only. Both test tubes were kept at 37 0 C. 3

4 D lipase bile salts + peanuts powder in water at 37 0 C Define the term enzyme. [2] Enzymes are chemical substances or proteins that act as biological catalyst. They speed up chemical reactions yet they remain unchanged and do not get used up in the reaction (b) Explain why the bile salts were added. [2] Bile salts emulsify fats in peanuts or break down fats to small particles to increase the surface area for digestion; (c) Explain why the temperature of the water had to be maintained at 37 o C. [2] 37 o C is the optimum or most suitable temperature for the enzyme action. It is the human body temperature since these are human enzymes. State the purpose of test tube D in the experiment. [1] Test tube D is a reference experiment for comparison. It is a control experiment. (e) The pupil added ethanol into each of the test tubes to test for fats. Describe what he would most likely observe in each of the test tubes. [2] Test tube D-There shall be no change. The solution will remain colourless showing that three in no fat. Test tube E-It shall turn milky or cloudy to show that fats are present. Q3 Plants are an important source of food for animals. The leaves play an important role in the making of the food. Name the substance that makes the leaves green. [1] E Chlorophyll; Name the mineral substance required by the plant to form the green pigment. [1] Magnesium ions. (c) Describe how light energy from the sun is converted to the chemical energy in starch during photosynthesis. [3] The green pigment in leaves, called chlorophyll traps sunlight energy and use it to react carbon dioxide and water to produce glucose is then converted to starch. (d) Describe the changes that occurs to the starch in maize in the human digestive system to make it ready for absorption into the blood stream. [4] Mechanical digestion by teeth in mouth first breaks down the food to small pieces. Salivary amylase in saliva starts chemical digestion of starch to maltose in the mouth. Pancreatic juice contains pancreatic amylase which continues the digestion of starch to maltose in the duodenum. The final digestion of starch takes place in the ileum where maltase digests maltose to glucose. Q4 (a) Menstruation is one of the secondary sexual characteristics in females. The figure shows the female s menstrual cycle starting on day 1. (i) Name the hormone responsible for the secondary sexual characteristics in females. [1] Oestrogen Menstruation O (Ovulation) 4

5 (ii) Mark on The figure49.1 with the letter O the day when ovulation is likely to occur. [1] Day 14 (marked with O on the cycle) (b) Supposing that the first day of menstruation was on January 17, State the calendar date when sexual intercourse is most likely to lead to pregnancy. [1] January 31 (January 30 and February 1 may be acceptable) (c) One of the earliest signs of pregnancy is the absence of menstruation. Name two methods by which pregnancy could be prevented. Give an example for each method. [2] Method 1: Chemical, Examples: Spermicides, the pill and injections Method 2: Mechanical: Examples: IUD, condom, sheath, diaphragm Method 3: surgical. Examples: vasectomy, BTL Method 4: Natural. Examples: rhythm, withdrawal, abstinence (d) A person developed a painless ulcer on the genitals which later disappeared on its own. A body rash accompanied with a high body temperature occurred in about six weeks. (i) Name the sexually transmitted infection (STI) the person was most likely to be suffering from. [1] syphilis (ii) Describe how this stage in the STI promotes the spread of HIV. [2] The open wound of the ulcer may allow exchange of blood and other body fluids with another person which may transmit HIV. (e) The terms below are commonly used in reproduction. Match the terms on the left with the correct definition on the right by drawing a line. The first one has been done for you. [4] Ovulation Implantatio n Fertilization Sexual intercourse Ejaculation (f) The following refers to the main stages of birth in a random order. List these stages in the correct order in which they occur starting with the first to the last one. I Amnion breaks. II Placenta expelled from the uterus. III The baby s head emerges from the vagina. IV Contractions of the uterus begin. [2] IV; I; III; II Q5 Water is needed by plants for several chemical processes. (a) Describe the movement of water: (i) from the soil into the roots [2] The water molecules, which are highly concentrated in soil solution than in cell sap, move from where they are more into the root hair cells where they are less, down their concentration gradient, across the selectively permeable cell membrane by osmosis. (ii) from roots to leaves. [2] The fusion of a sperm and an ovum The release of sperms into the female body Inserting the penis into the vagina The sinking of a fertilized ovum into the spongy lining of the uterus The release of ovum from the ovary The water molecules which are highly concentrated in the root hairs diffuse into xylem vessels where they are lowly concentrated. They 5

6 are pulled up the stem in the xylem vessels by the water potential gradient caused by the transpiration pull. The attractive forces of the water molecules hold together continuous columns of water in the very thin tubes by capillarity. (b) Most water in plants is lost from the leaves. Describe how each of the following would affect the rate of transpiration: (i) decreasing humidity [2] It will increase the rate of transpiration because the lower concentration of water molecules in the air than in the leaf cells will cause more water to diffuse out of the leaf into the air. (ii) increasing light intensity [2] It will increase the rate of transpiration because the light intensity will cause more stomata to open wide allowing more water vapour to escape from the leaves. (c) Lungile, an Agriculture pupil, forgot to water the spinach in her garden for five days during which there was no rain. Describe and explain the appearance of the spinach after five days. [2] The leaves will be looked droopy because of wilting. The cells will loose water and tugor and will be flaccid. Q6 The figure shows different blood vessels. G H I (a) (i) Which of the blood vessels G, H or I is a vein? [1] H (ii) State the feature that identifies a vein from the diagram. [1] It has thin muscle wall and a wide lumen. (iii) State the function of an artery. [1] It carries blood (oxygenated and deoxygenated) away from the heart to body tissues. (b) The figure shows some components of blood. J K L M (i) Identify a red blood cell from the figure. [1] J is a red blood cell (c) Plasma and white blood cells continuously leak out of the blood capillaries to form tissue fluid. Name two substances required by cells that are found in tissue fluid. [2] glucose, amino acids, oxygen, iron, calcium, iodine; vitamin A, C, D, etc. (any 2 named nutrients, minerals or vitamins) Q7 An athlete running a 400m race experiences change in the breathing rate and muscles start respiring both aerobically and anaerobically. Sometimes the athlete is unable to finish the race due to muscle fatigue. (a) (i) Describe what happens to the athlete s muscles that results in fatigue. [3] Muscles do not get enough oxygen and start to respire an anaerobically producing lactic acid. Lactic acid build up in the muscles causing fatigue. (ii) State one advantage of aerobic respiration. [1] It releases more energy (iii) Write a word equation for aerobic respiration. [2] glucose/sugar + oxygen; energy + carbon (b) Compare the rate and depth of breathing before and immediately after a race. [2] The rate is slower before race and faster just after the racethe depth is lower before the race and it is increased after the race (c) Describe the test for carbon dioxide. [2] Lime water changes to milky in the presence of 6

7 carbon dioxide Q8. Ayanda was stung on her arm by a wasp. This caused Ayanda to move her arm quickly away from the wasp. (a) (i) Complete the flow chart by putting the following terms in the boxes to show the route of the impulse from the time Ayanda was stung to the time she reacted. effector, receptor, response, stimulus. [3] stimulus Receptor N central nervous system O - PAPER 3 Q1. The figure shows part of a project carried out by a pupil to investigate the effect of ph on teeth. ph2 ph7 ph9 Response Effector (ii) Identify and name the neurons at N and O. [2] N is Sensory neurone O. is motor neurone (b) The central nervous system in Ayanda s reflex action is represented by the spinal cord. State the parts that represent the following. [4] (i) Effector: arm muscle (iii) Response: arm pulled or wasp sting (ii) Receptor: skin (iv) Stimulus: pain Q9 Down s syndrome is a condition caused by mutation, which results in variation. (a) Define the term mutation. [1] It is a spontaneous or sudden change in a genes or chromosome (b) State two causes of mutation. [2] Radiation, tobacco tar, carcinogens and mustard gas (c) Name the type of variation shown by blood groups in humans. [1] Discontinuous variation (d) Commercial crops are often made to yield better produce by genetic engineering. Define genetic engineering. [2] It is taking an advantageous gene from one species and putting it into another species (a) (i) Name the type of human tooth used in this experiment. [1] Incisor (ii) Describe how its shape makes the tooth suitable its function. [2] It is chisel shaped for cutting (b) After 24 hours, one of the teeth had become smaller in size and softer. In which test tube A, B or C did the tooth become smaller and softer? [1] In test-tube A A B C (c) Explain the importance of using the same type and size of teeth in this experiment. [2] It is to keep all other factors the same while varying the ph only (d) Some country authorities add fluoride into drinking water because, it is said to help prevent tooth decay. (i) Explain how fluoride helps to reduce tooth decay. [4] It stops plague formation, neutralizes acids in the mouth, kills bacteria and strengthen the teeth. 7

8 (ii) State two disadvantages of adding fluoride into the drinking water. [2] It colours teeth, it is expensive, it unnecessarily adds fluoride to the diet and the other uses of water do not need fluoride Q2. The figure shows the relationship between a group of alveoli and associated blood vessels. (iii) Describe the mechanism of inhalation, including reference to the action of the diaphragm. [4] The muscles of the diaphragm contract causing the curved diaphragm to flatten and become straight. The volume of the chest cavity increases and the air pressure inside the chest decreases. Air from outside moves into the lungs to balance the pressure. (c) Sometimes organisms release energy from muscles through anaerobic respiration. Using symbols, write a balanced equation for anaerobic respiration in muscles [2] C 6H 12O 6 2C 3H 6O 3 + (energy) (a) Name the types of blood vessels labelled D and E. [2] D: Artery E: vein (b) The alveolus is a structure involved in gaseous exchange. (i) From the figure identify and describe a feature of the alveolus, which makes it suitable for this function. [2] It is thin walled, for efficient diffusion of gases. It is moist to allow gases to dissolve and diffuse. It has a large surface area and they are many of them in the lung to speed gaseous exchange. It has a concentration gradient for continuous ventilation (ii) Oxygen is absorbed into the blood from the alveolus. Explain how this oxygen is carried in the blood. [2] It is combined with haemoglobin in red blood cells to form oxyhaemoglobin Q3. Wardens in a game reserve, wishing to reintroduce Panthera leo into the country, imported a group of the animals. Pantheraleo feeds on herbivores such as springboks and impalas. Leopards in the game reserve also feed on the impalas and springboks. The game ranger suspected that Pantheraleo also preyed on a protected bushbuck species. He fitted plastic collars with tracking devices on some of the protected bushbucks to monitor them. Many of the plastic collars were found next to the remains of dead bushbucks. The game ranger decided to move the surviving bushbucks to another game reserve. (a) The springboks and impalas are primary consumers. State the type of food that all primary consumers eat. [1] Vegetation such as plants and grasses (b) Name the two carnivores identified in this passage. [2] Panthera leo and Leopards. (c) Identify a food chain that includes Panthera leo and shows feeding relationship in the game reserve. [2] grass/vegetation/plants impalas/ springboks/ bushbucks Panthera leo (d) Define the term binomial system, and state an example used in the passage. [2] It is a system of naming organisms using the 8

9 genus and species; an example is Panthera leo; (e) Explain why the population of Panthera leo continued to survive even though there were no longer bushbucks on which to feed. [2] The Panthera leo depended on the other sources of food such as the impalas and springboks (f) Name the part of the central nervous system, which is damaged when Panthera leo breaks the neck of the bushbuck. [1] Spinal cord (g) Explain why the plastic collars of the dead bushbucks could create an environmental problem. [2] Plastic is non-biodegradable, it does not rot and disappear from the environment easily. It will cause pollution. It may entangle, suffocate or poison other organism for a long time; (h) Explain why it is an advantage for humans to feed more on green plants as primary consumers instead of being secondary consumers. [2] Energy is lost between producers and primary consumers, and more energy is lost between primary and secondary consumers. Therefore feeding on green plants will be energy efficient for humans. Q4 The figure shows a diagram of a set up of am experiment that was carried out by a group of pupils at Mpisi High school. The experiment was left for 24 hours. (c) State any two environmental factors that could have been controlled to make this experiment a fair test. [2] (d) Describe and explain the appearance of the jars after 24 hours. [8] (e) State the conclusion drawn by the pupils from the experiment. Q5 People of the same age may have different heights. (a) (i) Name the type of variation shown by the people s heights. [1] Continuous variation (i) State two factors that influence variation in people s height other than age. [2] Environmental and genetics or inheritance (b) Mutation is one cause of variation among human beings. One example of mutation is the incidence of sickle-cell anaemia. Describe sickle-cell anaemia. [2] It is a condition whereby the human red blood cells become sickle shaped and inefficient in carrying oxygen (c) Many people country wide are living in fear of contracting the deadly multi-drug resistant ( MDR) tuberculosis bacteria. Explain how this life-threatening type of bacterium has developed. [3] A person infected with TB stops taking the drugs before finishing the full course. The weaker TB bacteria are selected out and killed by the initial dose. The resistant bacteria that was supposed to be killed by the later dose of drug which was not taken, is left to multiply and mutate to produce more of the resistant strains. These bacteria cannot be treated by the drug it survived earlier. (a) Why were the cut ends of the stem smeared with Vaseline? [1] (b) Explain the role of the cellophane paper around the plant pot. [2] Q6. Some pupils carried out an experiment to investigate the effect of carbon dioxide concentration and light intensity on the rate of photosynthesis in a plant. The graph below shows the results of the investigation. 9

10 vitamin B 2 10% Benzoic acid (E210), pimaricin (E235) vitamin B 12 40% (a) Using information from the graph, State the light intensity required to produce a rate of 8 arbitrary units when using: [2] (i) 0.01% CO 2 : 2000 lux (ii)0.02% CO 2:: 1000 lux (b) Describe and explain how the rate of photosynthesis varies with increased light intensity. [4] As the light intensity increases, the rate of photosynthesis increases up to a maximum point and then remains constant. At the maximum point carbon dioxide becomes the limiting factor because the plant cannot absorb it any faster.\ Q7. The following labels were found on a container of two beverages (drinks), H and I, in one of the local super markets. The nutritional information for beverage I was not available. Beverages (drink) H Nutritional information per 100 ml serving energy 260kj carbohydrates 4.8g calcium 119mg proteins 3.4g fat 3.4g Recommended daily amount for persons older than 4 years phosphate 12% protein 6% Beverage (drink) I Ingredients: Sugar, milk, fruit concentrate, dextrose (E421), citric acid (E330), stabilizer, approved colouring & flavouring, sodium citrate. Preservative; (a) Explain why beverage H has a high nutritional value. [2] (b) Explain which beverage you would recommend for a patient suffering from scurvy. [3] (c) (i) Identify and name any two food additives from beverage I. [2] (ii) Describe the role of food additives. [3] (d) Explain why beverage I would not be suitable for an HIV positive person. (e) Suggest, with reason, the most likely name of beverage H. [2] 10