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(a) The following solution was expected from the candidates (b) (i) |QK| = 9.3cm (ii) < QRS = 55\(^o\)

(a) Marks Class Boundaries Frequency Cumulative Frequency 10 - 19 9.5 - 19.5 4 4 20 - 29 19.5 - 29.5 7 11 30 - 39 29.5 - 39.5 12 23 40 - 49 39.5 - 49.5 18 41 50 - 59 49.5 - 59.5 20 61 60 - 69 59.5 - 69.5 14 75 70 - 79 69.5 - 79.5 9 84 80 - 89 79.5 - 89.5 4 88 90 - 99 89.5 - 99.5 2 90 (b) The cumulative frequency curve (c)(i) using the curve, the median was 51.5. (ii) Using the curve, the estimate of tbe number of students who scored at least 75% was 90 - 80 = 10 Therefore, Prob(that a student selected at random obtained distinction) = \(\frac{10}{90} = \frac{1}{9}\)

(a) (i) The diagram can be represented as: (ii) first they were expected to convert from litres to cm\(^3 \) by using the fact that 1000 cm\(^3\) = 1 litre, then 4.158 litres = 4158 cm\(^3\). If the volume and height of the container were V\(_1\) and h\(_1\) respectively, then, V\(_1\) = \(\frac{1}{3}\) x \(\frac{22}{7}\) x 21 x 21 x h\(_1\) = 4,158 which simplified to 462h\(_1\) = 4,158. Therefore, h\(_1\) = 9cm. (b) let h\(_2\) be the height of the water remaining in the container. Then by similar triangles, \(\frac{h_2}{9}\) = \(\frac{14}{21}\), h\(_2\) = 6 cm. If we let V\(_2\) be the volume of water remaining in the container, V\(_2\) = \(\frac{1}{3} \times \frac{22}{7}\) x 14 x 14 x 6 = 1,232 cm\(^2\). Volume of water drawn out = (4,158 — 1,232) cm\(^3\) = 2,926 cm\(^3\)

(a) They sketched the required diagram as follows: (b) (i), using sine rule \(\frac{285}{\sin z} = \frac{307}{\sin 307}\) Then sin z \(\frac{285 \times \sin 78^o}{307} = \frac{285 \times 0.9781}{307}\) = 0.9080 Z = \(\sin^{-1}(0.9080)\) = 65.23\(^o\) The bearing of X from Z = 360\(^o\) - 65.23\(^o\) = 294.77\(^o\) \(\approx\) 295\(^o\) or N65\(^o\)W correct to the nearest whole number. (b)(ii) They obtained < YXZ = 180\(^o\) - 143.23\(^o\) = 36.77\(^o\) Then, using sine rule, \(\frac{\text{|YZ|}}{\sin 36.77^o} = \frac{307}{\sin 78^o}\) and computing for |YZ|, |YZ| = \(\frac{307 \times 0.5986}{0.9781}\) = 187.88m and Therefore, the distance between Y and Z \(\approx\) 188 m correct to the nearest whole number

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Euglena can survive in a dark room for a long time because it has the ability to switch from photosynthetic (using light) to heterotrophic or holozoic nutrition (absorbing nutrients from the surrounding environment) when deprived of light; essentially acting like a tiny animal by consuming organic matter in the water, allowing it to continue living even without photosynthesis through its chloroplasts.

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(a) Roles of the following compounds in respiration (i) Glucose Is broken down to give energy/ (ATP); carbon dioxide; and water is given off. (ii) Oxygen Oxidizes/ breaks down/ burns; the glucose, releasing energy completely. (b) Types of cellular respiration Aerobic; Anaerobic (c) Structures of gaseous exchange S/No. Organism Structures of gaseous exchange i. Amoeba Cell membrane/ entire body surface ii. Tilapia Gills iii. Adult toad Lungs, skin, buccal cavity iv. Grasshopper Trachea/tracheole (d) Diagram of an open stoma in leaf

(a) Process of conversion of food to chyme in the stomach of a mammal The stomach is a large thick-walled muscular sac; made of three layers of muscles; that contracts in different directions when food enters into it; bringing about a twisting/squeezing/churning effect; enabling food to mix with digestive juice; and HCL; this movement then converts food to the semi-liquid called chyme. (b) Table Enzyme Juice Food acted upon end product Pepsin ii. Gastric v. Protein viii. Peptone/ polypeptide Ptyalin/ amylase iii. Saliva/pancreatic juice vi. Cooked starch/carbohydrate Maltose Lipase iv. Intestinal/Pancreatic juice vii. Fats and Oil ix. Fatty acid and glycerol (c) Experiment to show that carbon dioxide is necessary for photosynthesis Two potted plants are de-starched by placing them in a dark cupboard for 24hours; a leaf each from both plants are then tested for starch to ensure they have no starch/have been de-starched; the potted plants are placed on a board each; a beaker containing caustic soda is placed beside plant A; to absorb carbon dioxide; while a beaker containing water is placed beside plant B as control; they are both covered with bell jars labelled A and B respectively; the rim/edge is smeared with vaseline/petroleum jelly to make it air tight; the setup is exposed to sunlight/light for 4-6 hours; a leaf each from both plants are plucked and tested for starch. Observation: It is observed that leaf from plant A is negative/does not contain starch/remains brown in colour while leaf from plant B is positive/contains starch/turns blue - black. Conclusion: Carbon dioxide is necessary for photosynthesis. OR De-starch a well-watered potted plant by putting it in darkness for 48 hours; insert a leaf into a flask containing water which serves as a control experiment; and another leaf into another flask containing KOH/ potassium hydroxide/ caustic potash; ensure both flasks are air tight by smearing the split corks with Vaseline; leave the potted plant in a well-lit place for 6 to 9 hours; detach the leaves and test them for starch. Observation: It is observed that the leaf in the flask containing caustic potash contains no starch while the leaf in the controlled experiment contained starch. Conclusion: Carbon dioxide is necessary for photosynthesis.

(a) (i) Ecosystem: Is a natural unit consisting/made up of living/biotic/organism and non-living/abiotic elements/factors; interacting to produce a stable system. (ii) Abiotic environment: The non-living components of the ecosystem; such as light/pH/water/oxygen/wind/temperature etc. (b) Ecological factors that are specific to: (i) Aquatic habitat Salinity; turbidity; tidal movement; dissolved gases; density; substratum; water current. (ii) Terrestrial habitat Humidity; soil; topography; wind; altitude; availability of water. (c) The relationship between grass and rabbit in a given habitat Grass (green plants) can photosynthesize/ manufacture its food; Rabbit which cannot manufacture its food feeds on grass; During respiratory process, rabbit gives out carbon dioxide as a waste product; Grass makes use of the carbon dioxide to manufacture its food; Grass during photosynthesis gives out oxygen as a by-product which the rabbit uses for respiration; When a rabbit defecates/ dies, bacteria/fungi cause its decay, which forms manure that is absorbed as soil nutrients by grass. (d) Pyramid of energy

(a) (i) Mendel’s laws of inheritance First law/law of segregation States that a pair of alleles/genes of contrasting character; segregates during gamete formation so that only one allele/gene enters a single gamete. Second law/law of independent assortment States that of a pair of alleles/genes of contrasting character; segregates independently; and combines randomly/distribute itself; with either of another pair of alleles/ genes. (ii) Applications of genetics in medicine Screening blood for transfusion; Determining paternity/ parentage; Marriage counseling for genetic disorders; Production of certain drugs/insulin; Sex selection in babies; Cloning of cells; Test-tube babies/ in-vitro fertilization; Organ transplant. Analysis of blood in crime detection. (iii) Disadvantages of inbreeding Loss of reproductive vigor/potency; Susceptibility to disease; Limited gene pool/lack of varieties; Inability to withstand environmental changes; Replication /retention of undesirable traits. (b) (i) Evolution The process of development of complex organisms; from simple forms; over a long period of time; and results in the origin of new species. (ii) Convergent and divergent evolution Convergent evolution produces similar structures in organisms; that have evolved from different unrelated ancestors; while divergent evolution produces modification of structures in organisms that have evolved from a common ancestor; due to adaptation to environmental changes.

(a) (i) Name of teeth A: Canine B: Molar C: Incisor (ii) Teeth found in position I, II and IV I – Incisor II – Canine IV – Molar (iii) Functions of each of the teeth A - Canine: For tearing flesh/ piercing. B - Molar: For breaking/ crushing/ chewing/ grinding. C - Incisor: For cutting/biting (iv) Reason for the answer A - Canine: It is conical/ sharp / pointed. B - Molar: It is broad with ridges/ cusps on surface. C - Incisor: It has (flat) sharp/ chisel-shaped edge. (b) Factors responsible for tooth decay Acid accumulation. Bacterial/microbial/fungal activity. Food remnants/sweet/sugary/sticky foods. Improper use of teeth can lead to cracks e.g. cracking hard bones with teeth, opening bottle tops with teeth. Lack of proper care of teeth/ unhygienic dental practices. Lack of fluoride/ vitamins/ minerals (in food). (c) Total number of teeth A/Canine: 4 B/Molar: 12 C/Incisor: 8 (d) The tooth that is absent in a rabbit A/Canine (e) (i) Name of tooth in III of diagram D Premolar (ii) Teeth absent in an infant Molar/IV (f) Care of the teeth in humans Brushing the teeth regularly/after meals/before going to bed; Avoiding smoking and excessive alcohol; Eating vitamins and mineral-rich foods regularly (fruits); Reducing the intake of sweet/sticky/sugary foods (that may allow bacterial growth); Visiting the dentist at least twice a year/every six months; Removing food particles from teeth using tooth pick; Washing/ flossing teeth with germicide solution e.g. hydrogen peroxide; Avoiding hard objects that may break the teeth, /e.g., removal of cork/bottle tops/cracking large bones. Scraping the plaque on teeth with appropriate material/ tool/ scrapper.

(a) Processes involved in water cycle Respiration by plants/animals; Transpiration; Surface run-off/erosion; Excretion by plants/animals; Decay of plants/animals; Precipitation /rainfall; Condensation of water vapor/ cloud; Absorption of water by root hairs; Evaporation; Percolation; Perspiration/ sweating; (b) Instruments for measuring the following physical factors pH – pH meter/pH paper/ colorimeter; Light intensity – light meter/photometer; Turbidity – Secchi disc; Temperature –thermometer. (c) Contributions to cell theory (i) Robert Hooke: He discovered the cell; while using a microscope to examine the cork from a tree bark; he observed honeycomb structures/dead cell walls surrounding empty holes; which he called ‘cells’. (ii) Theodore Schwann: Examined bits of different animals under the microscope; and observed that all animals are composed of cells. (d) (i) Nastism Refers to the non-directional response of plant organs/part of a fixed plant to external /non-directional or diffused stimuli/touch/temperature/humidity/( e.g. leaves of Mimosa plant folding up when touched); it is not a growth movement; it is reversible (e.g. 4-0-clock flower). (ii) Taxism It is not a growth movement; directional response of motile/whole organisms; towards / away from to an external stimulus/ light/ chemicals/ temperature; (e.g. Euglena swimming away from chemicals; Euglena swimming towards light, etc.) (e) Diagram of the human tongue showing areas of taste (f) (i) Ways through which microbes enter the human body Through some parts of the body/Mouth; mucous membranes/mucosa; anus; skin; birth canal /vagina; nose; Insect bite; Blood contact; Direct contact with infected person/animal; Body secretions/semen/saliva/sweat/vaginal fluids/tears/mucus; Food; Water; Inhalation/aerosol. (ii) Harmful effects of microbes to humans Causes various diseases in humans; Involved in spoilage of food; Causes death of humans; Destruction of materials/wood/cotton/leather/paper/any correctly named example.

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