Answer Perfect Score Biology 2009

PERFECT SCORE BIOLOGY 2009 PERFECT SCORE Biology 2009 MODUL II ESSAY QUESTIONS Question 1: Diagram 1 shows a reaction catalyzed by sucrase.

(a) Based on Diagram 1, explain the characteristics of an enzyme. (6 marks) · Enzyme is highly specific · M only can break down N because it has an active site which is fits to N molecule. · The enzyme reaction is reversible. · Substrate / complex molecule can be broken down by hydrolysis and · products can be converted to complex compound by condensation. · Enzyme does not destroy after the reaction / can be reused after the reaction · After the substrate is broken down into products, it leaves the active site of enzyme. (b) Enzymes are widely used in our daily life and industries. Based on the above statement, explain how enzymes are used in the food industry. [4 marks] · Lipase is used to react with fats in milk to produce cheese. · Protease is used to tenderise meat so that it can be consumed easily. · Cellulase used to separate agar from seaweed. · Zymase in yeast is used widely in the preparation of alcoholic drinks such as wine and beer. · Zymase acts with the glucose in grape juice during fermentation, thus producing ethanol, which is used to make wine. · Amylase is used to remove starch from fruits in the making of fruit juice. · In breweries, amylase is used to remove starch before the addition of malt. Question 2: A study is carried out on two individuals X and Y. They were asked to drink glucose solution of the same volume and concentration. The glucose and insulin level in the blood is measured. The graph in Diagram 2 shows the changes in concentration of glucose and insulin in the blood of

individuals X and Y. The concentration of glucose in a normal individual is 0.09 gdm-3

(a) Explain the differences between the graph of individuals X and Y in relation to: (i) blood glucose concentration (ii) insulin concentration in the blood [10 marks] · At stage 1, before glucose intake, blood glucose concentration in individual Y is normal which is 0.09 g/dm3 while blood glucose concentration in individual X is high (0.13 g/dm3). · Y is normal while X is suffering from diabetes mellitus. · At stage 2 after glucose intake, blood glucose level in individual Y increases until it reaches at maximum level (0.13 g/dm3) while blood glucose level in individual X increases rapidly and reaches at maximum level 0.20 g/dm3. · At stage 3 blood glucose level decreases rapidly in individual Y until it reaches at normal level (0.09 g/dm3) while blood glucose level in individual X decreases to 0.165 g/dm3. · Y is normal while X is suffering from diabetes mellitus. · At stage 1 insulin concentration in the individual Y is 0.02 arbitrary units before glucose intake while insulin concentration in the individual X is 0.01 arbitrary units. · After glucose intake / at stage 2, insulin concentration in the individual Y increases rapidly and reach the maximum level 0.06 arbitrary units while insulin concentration in the individual X is increases to 0.02 arbitrary units. · More insulin is required to convert excess of glucose into glycogen back to normal level while in individual X pancreas fails to secrete high concentration of insulin so glucose level is high. · At stage 3 that is after a few hours the concentration of insulin in the individual Y decreases and remain high in the blood (0.02 g/dm3) while in the individual X concentration of insulin is remain

low (0.01 arbitrary units). · Glucose level can be converted to the normal level in the individual Y while glucose level of X is high and X is suffer from diabetes. Question 3: Diagram 3 shows the longitudinal section through the thorax of a man.

Diagram 3 Describe briefly the mechanism of breathing in man . In your answer describe the part played by the (i) diaphragm (ii) intercostals muscle (iii) alveoli (10 marks) Answer: (i) · Diaphragm is a muscular sheet in the body cavity separating the thorax from the abdomen · At the start of inhalation, the muscles of the diaphragm contract , making it less arched · This helps to increase the volume of the thoracic cavity and reduce the pressure of the thoracic cavity. Air rushes into the lungs · When the muscles of the diaphragm relax , it returns to its arched condition , reducing the volume of the thoracic cavity and increasing the pressure of the thoracic cavity. Air is forced out of the lungs (ii) · The muscles between the ribs are known as intercostals muscles · During inhalation the external intercostals muscle contracts and raise the lower ribs · This helps to increase the volume of the thoracic cavity and reduce the pressure of the thoracic cavity. Air rushes into the lungs. · During exhalation the external intercostals muscles contract , the ribs return to their original position , reduce the pressure of the thoracic cavity. Air is forced out of the lungs

(iii) · The alveoli are thin-walled air sacs with the lungs · These sacs are surrounded by a network of capillaries · During inhalation the alveoli are filled with air and gaseous exchange occurs between the alveoli and the capillaries · Oxygen from the alveoli diffuses into the capillaries while carbon dioxide diffuses from the capillaries into the alveoli. Question 4: Why do we need to practice good posture? Explain how we can practice good postures while standing, sitting, walking and lifting heavy objects. [10 marks] Answer: · It helps to ensure that our body is always well supported · Then no undue pressure is placed on our muscles and spine · The internal organ such as the lungs, heart and stomach will be able to function properly · Muscles working properly prevent us from getting tired easily · It will prevent backache and shoulder ache · While standing our body should be erect and upright so that the weight of our body is supported by our feet · While sitting our back should rest against the back of the chair · We should maintain an upright position · While walking , our body should be upright and straight · Our head should be held high and our eyes looking straight ahead. · While lifting heavy object , we should bend both our knees and lift objects from the floor

Question 5: Reproduction technology has contributed a lot to human health and population growth. Describe how fertility is overcome in humans using the following methods: Sperm banking Artificial insemination In vitro fertilization Surrogate mother [10 marks] Answer: Sperm bank · used when the man/spouse/male suffers from low sperm count / production of weak / unhealthy sperm · sperms are donated and donor’s identity is recorded/ secret · genetic biodata of donor and the woman recipient should match for successful fertilization Artificial insemination · Practiced by a couple when the man is sterile · Donor’s sperm are injected into the woman uterus during ovulation · No sexual intercourse is involved · The genetic background and health of donor is screened before acceptance

In vitro fertilization · Practiced when the woman’s ovum cannot be fertilized due to blockage of fallopian tube · Ovum is extracted (from the woman) and fertilized outside the body / in petri dish / test tube · Fertilized ovum / zygote grows in culture medium · Than it is implanted into the woman’s uterus Surrogate mother · Method practiced when a woman cannot be pregnant in normal way · The zygote is obtained by in vitro fertilization · Another woman is implanted with the couple zygote · (surrogate mother) carries the baby only until it is born [any 10 points]

Question 6 The figure below shows a fluid mosaic model of the plasma membrane

(a) Explain the functions of the structures X, Y and Z in the movement of substances across the plasma membrane [4 marks] · Structure X allows hydrophobic molecules which can dissolve in lipids such as fatty acids, glycerol, steroid hormones, vitamins A, D, E and K to move in and out of the cell. · Structure Y allows bigger molecules which do not dissolve in lipids like glucose and amino acids to move in and out of the cell. · Structure Z allows small charged molecules to move in and out of the cell. (b) All movements of substances have to pass through a plasma membrane. Explain why the plasma membrane is known as a semi permeable membrane (6 marks) · The plasma membrane is known as a semi permeable membrane because it only allows the passage of certain molecules and limits the passage of other molecules. · It consists of two layers of phospholipids with protein molecules scattered in them · Molecules that can pass through the plasma membrane easily are those that can dissolve in lipid and small uncharged molecules. · Molecules which cannot move through the plasma membrane but require proteins include large molecules that do not dissolve in lipid and small charged molecules. · Channel protein does not require the binding of a molecule and conformational change to open. · Channel protein allows molecules to steadily diffuse across the membrane through diffusion.

· However a carrier protein allows specific molecules to cross the cell membrane by undergoing a conformational change upon the binding of the molecule. · The conformational change opens a hole through which the molecule can enter or leave a cell. Question 7: (a) Explain how the first line of defence can prevent the entry of pathogens into the body [6 marks] The first line of defence in the prevention of pathogens entering the body can be the function of (i) The skin · The skin serves as a protective layer against the entry of pathogens. The ph of the skin which is in the range of 3 to 5 provides an acidic environment which is not conducive for the growth of microorganisms. The enzyme lysozyme which is present in the sweat and sebum on the surface of the skin can kill microorganisms. (ii) The nose and respiratory tract. The mucous membrane that lines the respiratory tract can trap microbes, dust and foreign matter. The ciliated epithelium which lines the respiratory tract and the nasal cavity can remove the mucus when a person coughs or sneezes. (iii) The stomach. The hydrochloric acid in the stomach can kill the microbes that is present in the food that has entered the body. Besides all these, the body has natural reactions such as diarrhoea and diarrhoea that Can help to remove toxins and microbes very quickly before it is sent to other parts of the body.

(b) Explain the effect of taking fatty foods that have high cholesterol content to human healthy life. [4 marks] Our body has better ability to store fats rather than use it to release energy. As a result fats and excess cholesterol will settle on the arterial wall causing a condition known as arteriosclerosis. The lumen of the artery becomes narrow and hinders/slowing down the flow of blood, thus causing high blood pressure/hypertension. If the coronary artery is blocked, the supply of oxygen and nutrients to the heart is affected. This will cause a heart attack. If the flow of blood to the brain is blocked, there is a possibility that stroke can occur. Question 8: (a) Explain the principle involved in genetic engineering [2 marks] · Genetic engineering is a technique of manipulating the genes in an organism by removing a gene from one organism and transferring it to another organism (b) Discuss the importance of genetic engineering in the medical and agricultural field. [4 marks] The importance of genetic engineering in the medical field. · Production of insulin from bacteria.

· Gene from the pancreas that can produce insulin is removed and inserted into the DNA molecule of bacteria. · The bacteria that can produce insulin grows very fast in a suitable nutrient medium. · Insulin can be produced in large quantities in a short time. Genetic engineering in agriculture. · Produce food or plants which are genetically modified to produce high quality yield. · Produce plants with high quality yield as they are resistant to viral attacks, pesticides or predators.

(c) Diagram 8 shows DNA finger printing. DNA finger printing is more scientific, accurate and advanced compared to the thumbprint in criminal investigation.

Discuss the use of DNA fingerprinting in the identification of the parents of a child. Based on your answer, identify the father of the child. [4 marks] · DNA fingerprinting is a technique used to identify parents of a child based on DNA banding similarity · Generally, the DNA profile of a child is the combination of the mother and father. · A child inherit half of the chromosomes number from father and half from mother. · DNA fingerprinting gives more details and information regarding the identity of a person while thumbprints give general information as it is based on a few different types. · A blood sample, seminal fluid or any tissue can be analysed and its result is compared with that of an individual who is a suspect. · In conclusion, man P is the father of the child as the similarity of his DNA is higher Question 9: Diagram 9 shows organism, P, Q and R.

Diagram 9 (a) (i) Describe the type of nutrition in P and Q. [4 marks] P: Autotrophic that enables to produce their own food by photosynthesis process using simple inorganic substances to form complex organic substances Q: Heterotrophic unable to produce their own food, it depends to others organism for food (ii) Explain one similarity and three differences between the alimentary canal of Q and R. [6 marks] Both contain anaerobic bacteria and protozoa in their alimentary canal for digestion of cellulose Q R Has a very large caecum – to provide large compartment for digestion of cellulose Has small caecum – digestion of cellulose didn’t occur in caecum Has one stomach digestion of cellulose didn’t occur in stomach Has four stomachs; rumen, reticulum, omasum and abomasums – increase storage and digestion of cellulose Does not have diastema – because the main source of food is not grass/cellulose. Has a diastema to store cut cellulose before chewing by the molar

Question 10 Pregnant mother, infants and teenager require different energy daily. Each target group needs to choose a diet appropriate to its needs. Based on your biological knowledge discuss the above statement. [10 marks] Pregnant mother · Need rich in calcium and phosphorus for formation of strong bone in the growing of foetuses. · More folic acid and ferum for formation of red blood cells,/formation of normal neural tube development in the embryos · Rich of protein for the formation of new tissues · Eat lot of vegetables and grains as source of fibre to prevent constipation · Reduce a food rich in fats and sugar and caffeinated drinks to ovoid obesity and neural suppression

Infants and children · Infants need of lot protein, carbohydrate, lipid, vitamins and mineral, for muscle and bone development during growing process.

· Babies need a higher intake of calcium and phosphorus for the formation of bones and teeth. · Growing children need a diet rich in protein, vitamins, calcium and phosphorus for bone and tooth formation and promotes growth. · They also require more energy-rich food because they have higher basal metabolism rate than adult. Teenagers · Need food rich in proteins and vitamins during the period of rapid growth · Consumes rich of fruit and vegetable to supply vitamins and mineral, and ovoid constipation · Female teenager needs food rich in ferum to prevent iron-deficiency anaemia especially after menstruation. · Reduce intake of fatty and oily food to avoid having pimples and acne

Question 11: The diagram shows a human activity.

a) Explain briefly why humans carry out the activity as shown in diagram above. [4 marks ] b) Explain the important ecological roles of the tropical rainforest. [6 marks] c) i) Explain the impacts of the activity shown above on the environment. [7 marks] ii) Suggest methods to control the mentioned activity. [3 marks] Answers : a) - The human population grows rapidly. The demands for food and housing areas have increased. ( 1 mark ) - Vast areas of forest are cleared for agricultural and commercial purposes. ( 1 mark ) - Urbanization and industrialization have caused more forests to be cleared for road construction and housing areas. ( 1 mark ) - Deforestation is also caused by the demands for timber and fuel wood. ( 1 mark ) TOTAL 4 MARKS b) - The rainforest sustains almost half of the flora and fauna of the world. ( 1 mark ) - Certain plants from the forest provide food and pharmaceutical products to humans. ( 1 mark )

- The rainforest regulates the climate by influencing humidity, rainfall and temperatures. ( 1 mark ) - Green plants inside the forest absorb carbon dioxide from the atmosphere and maintain the concentration of the gas in the atmosphere. ( 1 mark ) - Green plants provide oxygen to all living things. ( 1 mark ) - The rainforest also acts as water catchment areas. ( 1 mark ) TOTAL 6 MARKS

c) - Deforestation causes soil erosion , landslides, flash floods and global warming. ( 1 mark ) - Causes the soil to become loose and less stable. ( 1 mark ) - Without the protection of green plants, the soil is exposed to the forces of wind and rain. ( 1 mark ) - The top layer of soil is washed away gradually by the rainwater. This is known as soil erosion. ( 1 mark ) - Soil erosion causes the depletion of minerals from the soil, therefore the soil becomes infertile and unsuitable for agriculture. (1 mark ) - Landslides may happen on steep hillsides during heavy rain. It is because rainwater flows quickly and causes the top layer of the soil to crumble. ( 1 mark ) - Rivers and drains are silted and the flow of water is blocked. ( 1 water ) - Therefore, water flows inland and this causes flash floods in the lower areas during rainy seasons. ( 1 water ) TOTAL Max 7 MARKS d) - Deforestation can be controlled by passing stricter laws to protect the forest. ( 1 mark ) - Through education, the public should be taught on the importance of the forest. ( 1 mark ) - New trees should be planted to replace trees which have been out drawn. ( 1 mark ) TOTAL 3 MARKS Question 12: Activities that carried out by the human to provide food, power and industrial needs have a extensive effects on the environment. These effects include atmospheric pollution, water pollution, destruction of habitats and communities and a natural phenomenon known as the greenhouse effect. d) Explain the fenomena of greenhouse effect and problems caused by this fenomena. ( 10 marks ) e) Suggest two measures which can be employed in the management of development activities and the ecosystem to ensure that the balance of nature is maintained. ( 10 marks )

ANSWERS a) Able to define and describe the causes and effects of greenhouse effects. · The greenhouse effect is caused by specific gases which form a thin layer around the atmosphere. ( 1 mark )

· These gases include (water vapor )/ carbon dioxide/ methane/ ozone/ nitrogen oxides and CFCs – any 2 gases ( 1 mark ) · The increased concentrations of atmospheric carbon dioxide is primarily due to - combustion of fossil fuels ( 1 mark ) - increased deforestation ( 1 mark ) - industrial production ( 1 mark ) Max 2 marks · The greenhouse gases allows short wavelength radiation from the sun to reach the earth’s surface. ( 1 mark ) · Some of the infra-red radiation fails to pass back through the greenhouse layer. - more heat is trapped in the atmosphere ( 1 mark ) - results in global warming ( 1 mark ) · Polar ice caps may melt - causing the sea to rise / extensive floodings ( 1 mark ) - subsequent reduction in land mass ( 1 mark ) - some aquatic populations would increase ( 1 mark ) - some terrestrial populations decrease ( 1 mark ) Max 2 marks · Climatic changes occur - rainfall changes ( 1 mark ) - heat increases ( 1 mark ) Max 1 mark TOTAL 10 marks b) Able to list the following measures and its examples · The practice of biological control Use natural predators to control the population of pest species ( 1 mark ) · Examples: - The use of caterpillars of the Cactoblastis cactorum to control the population of the prickly pear cactus. ( 1 mark ) - The use of (khaki chambel) to control the population of gold snails which feed on paddy stalks. ( 1 mark ) ( or any suitable examples ) · Biological control is better than using chemical control because ( 1 mark ) - the use of pesticide is indiscriminate and harmless organisms can be killed. ( 1 mark ) - the effects of pesticides can be persistent and remain in the environment for long periods. ( 1 mark ) ( or any suitable explanation) Max 4 marks · The use of renewable energy · examples of renewable energy - solar energy ( 1 mark ) - geothermal energy ( 1 mark ) (or any suitable examples) · Renewable energy occurs naturally in the environment is inexhaustible/does not pollute the

environment ( 1 mark ) Max 2 marks · The use of technology ( 1 mark ) · Use of unleaded petrol ( 1 mark ) - reduce the emission of lead into the atmosphere ( 1 mark ) · Use of microorganism to clean up the environment ( 1 mark ) - certain bacterias are used to break down oil spills at sea. ( 1 mark ) · Install catalytic converters in vehicles ( 1 mark ) - convert the harmful gases released during combustion of fossil fuels to less harmful products. ( 1 mark ) (or any suitable examples) Max 4 marks TOTAL 10 MARKS Question 13: (a) The shaded area of the graph in Diagram1 shows the intake of oxygen by an athlete before, during and after running for five minutes.

Period of running Key Oxygen demand Oxygen consumption 0 5 10 15 20 25 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.0 Oxygen consuption (litre per minute) Time (minutes)

Based on the graph , explain how an oxygen debt is built up when an athlete is running and how it is settled after he stops running. [ 10 marks ]

Answer - During a vigorous exercise (running), the breathing rate is increased. [1 mark] - This is to supply more oxygen to the muscles for rapid muscular contraction. [1 mark] - However, the supply of oxygen to muscles is still insufficient [1 mark] - and the muscles have to carry out anaerobic respiration to release energy. [ 1 mark ] - The glucose is converted into lactic acid, with only a limited amount of energy being produced. [ 1 mark ] - An oxygen debt builds up in the body, when no oxygen use in energy production [ 1 mark ] - High level of lactic acid in the muscles cause them to ache. [ 1 mark ] - After running, the athlete breathes more rapidly and deeply than normal for twenty minutes [1 mark ] - There is recovery period after 10 minutes until it reaches 20 minutes when oxygen is paid back during aerobic respiration. [ 1 mark ] - About 1/6 lactic acid is oxidized to carbon dioxide, water and energy. [ 1 mark ] Max 10 marks Question 14: 1. The diagram shows a terrestrial ecosystem. eagle

bird rat snake earthworm Explain how energy flows through the food chain and how it is lost to the environment. [ 8 marks] Answer : - Energy flows through the food chain in one direction [ 1 mark] - In the food chain, the plant is the producer, the rat is the primary consumer, the snake is the secondary consumer and the eagle is the tertiary consumer. [ 2 marks] // In the food chain, the plant is the producer, the earthworm is the primary consumer, the bird is the

secondary consumer and the snake/ eagle is the tertiary consumer. - Each level of food chain is called a trophic level. [ 1 mark ] - Energy is transferred from one trophic level to another trophic level [ 1 mark ] - When energy is transferred from one trophic level to another level as much as 90% of the chemical energy in the food consumed by primary consumer is used for its metabolic activities and lost as heat ` [ 2 marks ] - Only 10% of the energy in an organism is passed on to the organism at the next trophic level [ 1 mark ]

[10 marks] Question 15:

The figure above shows a type of transport which happens on the plasma membrane of a cell. Based on the diagram above, name the type of transport in the above figure. Explain your answer. [6 marks] Answer : - Active transport - is dynamic and requires energy / ATP for the transfer of molecules or ions - an area of low concentration to an area of high concentration through the living cell membrane.// go against the concentration gradient - It requires carrier protein - The carrier protein must be able to change its shape (and also be able to return to its original state.) - To combine the active site of the carrier protein with the molecules or ions. - To carry the complex molecular carriers through the plasma membrane.

Question 16: The figure shows the organelles involved in the production of extracellular enzymes.

(a) (i) Using a name example, explain the term extracellular enzyme. [2 marks] (iii) Based on the organelles shown, explain how extracellular enzymes are produced. [8 marks] (b) The figure shows a reaction of an enzyme and its substrate

Explain the mechanism of the enzymatic reaction [10 marks] Answer: ( a) (i) - Extracellular enzyme is produced in a cell, then packed and secreted from the cell. It catalyses its reaction outside the cell. An example is amylase. - (ii) The instruction for making the extracellular enzyme is transcribed from the deoxyribonucleic acid o (DNA) to ribonucleic acid (RNA) in the nucleus. o The RNA then leaves the nucleus through the nuclear pore o and attaches itself to the ribosome located on the endoplasmic reticulum. o When the synthesis of the enzymes is completed o it is encapsulated in a transport vesicle which fuses with the golgi body. o In the golgi body, the enzyme is further modified before being packed in a secretory vesicle. o The secretory vesicle transports the enzyme to the plasma membrane, where it fuses with it o and the enzyme is released outside the cell.

(b) The explanation of enzyme action is known as the ‘lock and key hypothesis’. · The substrate molecule fits into the active site of the enzyme molecule. · The substrate is the ‘key’ that fits into the enzyme ‘lock’. · Various types of bonds such as hydrogen and ionic bonds hold the substrate · in the active site forming the enzyme-substrate complex. · Once the complex is formed, the enzyme changes the substrate to its product. · The product leaves the active site. · The enzyme is not altered by the reaction and it can be reused.

Question 17: Discuss the uses of enzymes in the household & industries. Why are enzyme used in these industries.

Answer Enzymes are used as biological detergents. · Protease degrades coagulated proteins into soluble short-chain peptides. · Lipase degrades fat or oil stains into soluble fatty acid and glycerol. · Amylase degrades starch into soluble shorter-chain polysaccharides and sugars. Enzymes are used in the baking industry. · Protease is used in the breakdown of proteins in flour for the production of biscuits. · Amylase is used in the breakdown of some starch to glucose in flour for making white bread, buns and rolls. Enzymes are used in the medical field. · Trypsin is used to remove blood clots and to clean wounds. · Various other enzymes are used in biosensors. Enzymes are used in industries because: ·They are effective. ·They are cheap and easy to use. ·They can be re-used, thus only small amounts are needed. · They don't require high temperature to work, thus this reduces fuel costs. Question 18

Diagram above shows the structure of HIV. The virus infects helper T cells of the human ‘s immune system that caused AIDS, Acquired Immune Deficiency Syndrome. i) Descibe the effects of the human immunodeficiency virus (HIV) on the body’s defence mechanism. ( 6 marks ) ii) Suggest ways to prevent the spread of Acquired Immune Deficiency Syndrome (AIDS). ( 4 marks ) ANSWERS 2 (i) - HIV infects helper T cells. - Helper T cells are essential to activate other lymphocytes in the body’s defence mechanism against diseases. - There may be a long incubation period of several years for the virus before the symptoms appear. - The immune system of the infected person gradually becomes weakened and defenceless against many pathogens. - HIV also attacks the central nervous system. - There is weight loss and a decrease in the function of the nervous system. ( 6 marks ) (ii) - By practice sexual abstinence or only having sexual relationship with one partner. - Use condom during copulation/sexual relationship. - Set up centres to exchange free sterile syringe and needles for used ones to reduce the practice of sharing needles amongst drug users. - Strict screening of blood before it is used for transfusion. -Carry out awareness campaigns to educate public and schoolchildren about the dangers of AIDS. - Proper counseling provided to HIV positive person so that they do not spread the virus to other healthy people. ( Any 4 answers)

Question 19

Figure shows cells P and Q undergoing cell division. M (a) Based on the cell division of P, explain the best technique can be used by an oil palmer to produce a large number of oil palm in a short time. State one problem to be considered in using technique. The technique can be used is cloning and culture tissue. Tip of shoot/root namely explants is cut And cultured into the medium that contain nutrient/ hormone and the temperature Is kept constant at the optimum temperature and sterile (in vitro). Explant divides actively by mitosis to produce large number of cells namely callus. Callus differentiates to form shoot and root. Plantlets / clones are formed. The disadvantage of cloning is no variation. Clones are exactly identical to parent cell. If one clone is infected by disease, the others will be infected too because they have same resistance to the certain disease.

(b) A farmer wants to produce large number of goat A in a short period time. He tries to apply the concept of cell division cell P to produce new individuals of goat A. Describe the technique used. Justify the technique. The somatic cell (diploid cell) of goat A is taken and the nucleus of goat A is removed. An egg cell of goat B is removed and the haploid nucleus of goat B is removed. The diploid nucleus of goat A is inserted into the egg cell of goat B. The egg cell contain the diploid nucleus is cultured into the medium that contain nutrient and the condition is aseptic. The cell divides by mitosis to produce large number of cells namely embryo. Embryo is implanted into the uterus of goat B. A farmer should use the technique because by this he can select good characteristics of goat A and produces large number of offspring in short period time. So production yield can be increased. The disadvantages are no variation between individuals produced. Clones A are identical and have same resistance to the diseases. (c) Explain how the daughter cell produced differs than parent cell. The daughter cell produced differs than parent cell in aspect of the number of chromosome and the recombination of DNA. During prophase 1, chromatids of the homologous chromosomes cross over. After that the DNA is exchanged/ recombined Recombination of DNA causes variation among the daughter cell produced. During anaphase 1 each of homologous chromosome are separated and pulled at the opposite poles After meiosis 1 each daughter cell carried half number of chromosome than parent cell. Now genetically the daughter cells produced are different as compared to the parent cell.

Question 20: Diagram 18.1 shows parent cells undergoing cell division.

Cell division a) Based on the Diagram 18.1 i) What is the process shown ? State the significant of the process. [ 4 marks ] · The process shows parent cell undergoes mitotic division. · The significance of mitosis are to increase the number of daughter cells. · So new daughter cells produced causes growth in an organism. · In asexual reproduction, daughter cells produced are identical to parent cell. · If epithelial cells of skin damaged, the parent cell (Malpighi layer divides to produce new daughter cell. By this way daughter cell produced can replace or repair the damage cell. · The production of the daughter cells by mitosis can be applied in cloning or tissue culture. So new individuals can be produced in large numbers and at short time.

b) Diagram 6.2 shows a group of cells that is exposed to ultraviolet ray.

DIAGRAM 18.2 The exposure drives the cell cycle malfunctions. Based on the Diagram 18.2 describe the effect of cell cycle malfunctions to the body. [ 6 marks]

Formation of an abnormal cell (cancerous cell) Due to the DNA of the normal cell changes spontaneously (mutation) So the cell divides by uncontrolled mitosis To produce an abnormal cells That has two nuclei (without cytokinesis). These abnormal cells diffuse into the blood or lymph and transported by the blood circulatory system or lymphatic system To the other parts of the body cells. So it spreads to other organ and destroys the normal cells.

(d) Cancer is a disease which causes uncontrolled growth of tissues. Suggest the method to treat cancer. Explain how this treatment stops the growth of cancer cells. Radiotherapy is a method to treat cancer. Radiotheraphy contain radioactive rays. Radioactive rays is exposed and destroys the cancerous cells. Cancerous cells cannot divide and increase the number.

Question 21:

Figure 19.1 shows the structure of leaf. Figure 19.2 shows the organelle M involves in the formation of starch in plants. Based on the raw materials (inorganic substances) required in photosynthesis, explain the formation of starch(organic substance) in the plant. [10 marks] Carbon dioxide and water are the raw materials needed in photosynthesis to form starch with the presence of chlorophyll. During the light reaction, water is splitted to hydrogen ion and hydroxyl ion and release ATP When chlorophyll traps/ captures light The process namely photolysis of water Hydroxyl ion gives electrone to form hydroxyl group Hydroxyl groups combine to produce oxygen and water Hydrogen ion receives electrone to form hydrogen atom. Hydrogen atom enters the dark reaction To reduce carbon dioxide into glucose and water Using energy / ATP provides from the light reaction. Molecules of glucose undergo condensation to form starch.

Question 22

Why this food can be kept longer compared its normal condition.

- Cooked prawn - Frozen meat - Dried prunes 8 marks ] Answers : - beyond 60ºC in cooking process, the growth of microorganism is inhibited. [ 1 mark ] - microorganisms and their spores can be destroyed at temperature of about 121ºC. [ 1 mark] - Therefore, cooking the food properly will kill microorganisms and cooked prawn can be last longer compared to uncooked prawn. [ 1 mark ] - The temperature in refrigerator is low and microorganism become inactive. [1 mark ] - The optimum temperature for microorganisms to become active is between 35ºC - 40ºC, [1 mark ] - Moist medium is suitable for the growth of microorganisms because water is basic needs for microorganism. [ 1 mark] - Low moisture in refrigerator will slow down the spore germination. Therefore frozen meat can be kept within few months. [1 mark] - Dark condition and the moist at room temperature will give high chance for the growth of microorganisms in fresh food such as fruits. [1mark] - When prunes is exposed to ultraviolet rays and high intensity of sunlight , the light can kill the microorganisms in the fruit. [ 1 mark] - The dried food contains less moisture and less nutrients which may decrease microorganisms keep growing. [ 1 marks]