NAME........................................................................................CLASS...............ADM…………. DATE……………………….SIGN………………………………SCHOOL…………………… 231/1 BIOLOGY PAPER 1 MARCH- APRIL 2024 TIME: 2 HOURS MOKASA 2 EXAMINATIONS PAPER 1 MARKING SCHEME (Kenya Certificate of Secondary Education) BIOLOGY THEORY Instructions Write your name, class and admission number in the space provided above. Write the date of the examination and sign in the space provided above. Answer all the questions in the spaces provided. You may be penalized for wrong spelling especially technical terms. For Examiner’s Use Only QUESTION MAXIMUM SCORE CANDIDATES SCORE 1-31 80 This paper consists of 10 printed pages. Candidates should check the question paper to ascertain that all the pages are printed as indicated and no questions are missing. C:\Users\THIS PC\AppData\Local\Microsoft\Windows\INetCache\Content.Word\Screenshot_2024-07-04-10-50-14-28_40deb401b9ffe8e1df2f1cc5ba480b12.jpg 1. Name the cell organelles that carryout the following functions. (3mks) (i) Destroy old and worn-out organelles Lysosomes (ii) Formation of spindle fibres Centrioles (iii) Osmoregulation Contractile vacuole 2. i) State the importance of rings of chitin in the tracheal system of insects. (lmk) Keeps the trachea open and prevent it from collapsing during breathing. ii) Explain the significance of maintaining a steep concentration gradient in the respiratory surfaces of animals. (lmk) For maximum exchange of respiratory gases/ for efficient diffusion of respiratory gases 3. The diagram below is an apparatus used in Biology research a) Identify the apparatus and state its function Identity (1mk) Specimen bottle Function (1mk) Storage of specimen; b) State one precaution while carrying out research using the apparatus (1mk) c) Return all live specimen to their habitat to maintain ecological balance d) Do not destroy the specimen natural habitat e) Do not harm specimen features to avoid distorting the specimen features 4. Study the diagram below and answer questions that follow (a) State the division the organism belongs (1mk) Bryophyta rej; bryophyta (b) Name the parts labelled K and L (1mk) K- Capsule L- Seta (c). What is the function of the part labelled M. (1mk) \ Anchorage Absorption of water and mineral salts 5. What is the role of heparin in blood? (1mk) Prevent blood clotting in the blood vessles/ it is an anti-clotting factor 6. State two importance of water in germination (2mks) Softening seed coat; Activates enzymes Hydrolyses stored food 7. (a) What happens to excess fatty acids and glycerol in the body. (1mk) They undergo condensation reaction to form lipids i.e fats that are then stored in the subcutaneous layer of the skin 8. Tar present in burning tobacco has been found to be carcinogenic leading to lung cancer. a. Name a plant waste product that can be used in lung cancer therapy. (1 mark) Colchicine b. State two means of lung cancer treatment. (2 marks) Radiotherapy to destroy cancerous cells Temperature (oC) 10 20 20 40 50 60 Rate of respiration P C D Chemotherapy to relieve the pain and destroy cancer cells Surgery to remove the tumour 9. (i) Explain two ways in which the excretory system adapts the desert rat to water conservation. (2 marks) =Has a long loop of henle to increase the surface area for selective reabsorption of water back into the blood stream. _has fewer glomeruli to reduce the rate of ultrafiltration thus enabling the organism to conserve more water in the body (ii). Give the functions of the following parts of human eye: (a) Lens (1mk) . Adjust to focus an image of far or near object to the retina (b) Ciliary body. (1mk) - Has glands which produce / secret the aqueous humour; -Has muscles which contract / relax to change shape / surface of lense 10. a) Explain the roles of the following plant hormones (2mks) i) IAA Stimulates cell division and elongation; Apical dominance; Response e.g to light; ii) Gibberellins Stimulates cell elongation; Ripening of fruits; Flowering; Germination; f) Name one plant hormone responsible for germination of seeds (1mk) Gibberellins; Auxins; Cytokinin 11. The graph below shows the effects of temperature on the rate of reaction of the enzymes salivary amylase 8 065 (a)(i) Account for the changes in the curve between C and D (2mk) Temperature beyond the optimum denatured the enzyme resulting to the decrease in the rate of respiration. (ii) What does the dotted line represent? (1mk) The optimum temperature for the function of salivary amylase enzyme 12. A student wrote the scientific name for fungus causing potato blight as phytophthora Infestans. State two mistakes made by the student while writing the name (2mks) Starting generic name with small letter; Starting specific name with capital letter; Not underlining separately; 13. After a person had swum the length of a pool and climbed out of the water their skin temperature is likely to be very low but their deep body temperature is likely to be normal Why is the skin surface likely to be cold for sometime after leaving water? (2 marks) Water on the skin surface evaporate carrying away with it the latent heat of vaporization making the skin to be cold 14. The graph shows pressure changes in the left atrium and in the left ventricle during the heart beat. What is the state of the following valves at time x (i) Semi lunar valve in the aorta (1 mark) Opened C:\Users\THIS PC\AppData\Local\Microsoft\Windows\INetCache\Content.Word\Screenshot_2024-07-08-19-13-44-68_6012fa4d4ddec268fc5c7112cbb265e7.jpg retort flask germinating seed germinating seed sodium hydroxide sodium hydroxide (ii) Bicuspid valve (1 mark) Closed 15. a. What is asexual reproduction (1mark) Mode of reproduction where a single organism gives rise to offspring of same species without fusion of gametes; b. Name any two forms of asexual reproduction (2marks) Binary fission; Sporulation; Budding; Fragmentation; 16. Name the hormone responsible for development of secondary characteristic in females (1mk) Oestrogen; 17. The diagram shown below shows representation of one organism in the five kingdoms. Examine it carefully and answer the questions that follow a. Identify the organism (1mark) Bacterium; b. Name the Kingdom in which the above organism belongs (1mark) Monera; rej; monera 18. The diagram below shows an experiment that was set up to investigate germinating seeds. Beginning of experiment End of experiment (a) What changes are observable at the end of experiment? (1mk) The sodium hydroxide level rose in the retort flask; (b) Explain the change observed in (a) above. (2mks) Germinating seeds used oxygen and gave out carbon (IV) oxide; the carbon (IV) oxide was absorbed by sodium hydroxide and sodium hydroxide rose to occupy the space initially occupied by oxygen (c) Name the chemical process being investigated. (1mk) Respiraton 19. Define the following terms a) Mycology (1mk) Scientific study of Fungi b) Binomial nomenclature (1mk) A system of assigning a scientific name to organisms composed of two parts;(generic name and specific name) 20. Name two organism that form lichens (2marks) Fungus; Algae; 21. (a)Name one example of a characteristic in man transmitted by multiple alleles. (1mk) ABO blood grouping (b). What are the vestigial structures? (1 mark) Are structures that have reduced in size and become functionless in the course of evolution due to disuse.(OWTTE) 22. Name the tough fibrous band of connective tissue that holds the bones together at a moveable joint (1mk) Ligament 23. The diagram below illustrates the life cycle of a certain member of Division in kingdom Plantae. Study it and answer the questions that follow. (a). State the name given to this type of life cycle (1mk) Alternation of generation (b) Identify the dominant generation in the fern represented by the life cycle above (1mk) Sporophyte (c) State another division in which such a life cycle is present (1mk) Bryophyta/Spermatophyta 24. The diagram shows the percentage of tongue rollers and non-rollers in a human population. (i)what name is given to this type of variation? (1mk) Discontinuous variation (ii) Give two features of the above named type of variation (2mks) - They are controlled by one or two major genes - Physical expression of these genes is not influenced by the environment - Clearly defined /distinct differences/no intermediate forms 25. Study the genetic cross illustrated below and answer the questions that follow. When F1 was selfed 1064 plants were counted. State the ; (i) Genotypic ratio of F2 plants (1mk) 1TT;2Tt;1tt (ii) Number off tall plants and short plants in F2 generation (1mk) Tall plants 3/4x1064=798 Short plants 1/4x1064=266 26. It is known that weight lifting exercises in men causes muscles to grow bigger. However, the children of such men are not born with big bulging muscles. Explain (2mk) Changes in the phenotype which do not affect the genotype/gametes; cannot be inherited; 27. (a) State two features of nerves which increases the speed of nerve impulse transmission along them (2mks) Presence of myelin sheath to insulate axon Presence of nodes of ranvier to propagate nerve impulses (b). Distinguish between pyramid of numbers and pyramid of biomass (2mak) - Pyramid of numbers express the number of organisms in a measurable way starting from the greatest to the least; while pyramid of biomass is the constant dry weight of an organism at a given 28. The diagram below shows the human brain. Give the significance of the folds on the surface of the part labeled E (1mk) Increase surface area for attachment of nerves Which labeled parts of the brain are involved in the following activities (2mks) (a) Gasping for air after holding breath for sometime D (b) Ability to memorize and recite a poem during music festivals B 29. Explain what causes the tendrils of a pea plant to coil around stems of other plants.(3mks) Contact; causes lateral diffusion/migration of auxins to side away from contact; higher concentration of auxins at side away from contact stimulates rapid/faster cell elongation; leading to coiling around the stem. 30. State two structural differences between biceps muscles and muscles in the arteries in a human being. (2mks) Biceps (skeletal Smooth muscle(arteries Has cross striations Lacks cross striations multinucleated Uninucleated 31. Plants with non woody stems have various devices of getting support. State three methods by which this is achieved. (3mks) Twinning/coiling Thorns/hooks/spines Turgidity of parenchyma cells 32. The diagram below illustrates the results obtained in an experiment done to investigate a certain factor that affects the process of osmosis. (a) Account for the results in set up; (i) A (2mks) Starch is osmotically inactive; hence does not develop osmotic pressure and water does not move from the beaker into the visking tubing; hence the visking tubing has no observable change. (ii) B (2mks) Glucose in the visking tubing is osmotically active; develops osmotic pressure and distilled water moves from the beaker into the visking tubing by osmosis making it swell/increase in contents.