K.C.S.E Biology Q & A - MODEL 2018PP2QN06
The effect of auxin concentration on growth response of two parts of a plant, X and Y was investigated over a period of time. The results were tabulated as shown in the table below.
(a) On the same axis, draw line graphs of the effect on growth of the two parts, X and Y (percentage inhibition or stimulation) against the concentration
(b) With reasons, name the two parts of the plant, X and Y. X Reason Y Reason (c) From the graph identify: . (i) the point at which the percentage stimulation was the same for both X and Y. (ii) the optimum concentration of auxins required for part Y (d) State three ways in which the effects of auxins on plants is applied in flower farming. (e) Distinguish between simple and conditioned reflex action
answers
b) X—root;
Reason Low auxin concentration stimulates (rapid/faster) cell division and elongation/growth in roots; High concentration of auxins inhibits growth in roots; Y—shoot; Reason Low auxin concentration has little effect on the growth of shoots/shoots are stimulated to grow with high auxin concentration (up to a given optimum); c) i. 33%±2; ii. 1.0 parts per million; (d)Faster maturity of flowers/earlier flower formation/flowering; Prunning/decapitating shoot tips to allow sprouting of lateral buds, hence more yield; Keeping flowers fresh; Stimulate formation/development of (adventitious) roots;
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K.C.S.E Biology Q & A - MODEL 2018PP2QN05
The photograph below represents a plant in a Certain Division
​(a) (i) Name the Division to which the plant belongs.
(ii) With reference to the Photograph, state three observable features of the Division named in a(i) above. (b) Name the part labelled N and P. N P (c) Explain how the part labelled Q is adapted to its function
answers
​a) i. Bryophyta;
ii. Has capsules (for enclosing spores); Has (long) setae (for supporting the capsules/for effective propagation of spores); (Developed) rhizoids (for anchorage/absorption of water/mineral salts); Thalloid in nature/Thallus/undifferentiated; b) N — Capsule; P—Seta; (c)Numerous/hair-like to increase the surface area for absorption;/to enhance rate of absorption of water/nutrients/dissolved mineral salts; Numerous/hair-like to hold firmly on the surface/not to be easily blown away/displaced/anchorage; K.C.S.E Biology Q & A - MODEL 2018PP2QN04
The diagram below illustrates the arrangement of bones in a human arm.
​(a) Name:
(i) the type of joints formed at points H and M. H M (ii) bone G (b) Name bone J and state how it is adapted to its functions. Name Adaptation (c) State one functional difference between a tendon and a ligament.
answers
​a) i. H-Ball and socket (joint);
M - Gliding/planar/plane ii. Clavicle; b) Scapula; Has a spine to increase surface area for muscle attachment; It is broad/flat to increase the surface area for muscle attachment; Forms flexible attachment above the ribs that allows movement of the arms; Has a glenoid cavity/depression for articulation with the humerus/forming the ball and socket joint; Has acromion for articulation with clavicle/for muscle attachment; Has coracoid process to increase surface area for muscle attachment; c) Ligaments hold the bones together (at a joint) while tendons attach muscles to bones; K.C.S.E Biology Q & A - MODEL 2018PP2QN03
The amount of blood flowing tough certain pans in the mammalian body at different activity levels was measured and results tabulated as Shows in the table below.
​(a) Account for:
(i) the high blood flow through the cardiac and skeletal muscles during strenuous exercises. (ii) the results obtained for the alimentary canal at rest. (b)Name two waste materials excreted by both the skin and the kidneys.
answers
K.C.S.E Biology Q & A - MODEL 2018PP2QN02
Below is a graphical representation of students’ height in a classroom.
​(a) Name the type of curve illustrated.
(b) (i) State the type of variation represented by the curve. (ii) State two meiotic processes that lead to variation among organisms. (iii) Explain the role of variation in organisms. (c) Explain the need for genetic counselling in present day health facilities.
answers
​a) Normal distribution curve;
b) i. Continuous (variation); ii. Independent assortment; Crossing over; iii. Organisms/individuals with advantageous traits/variations are favoured/selected by nature; and survive to reproduce/pass on/propagate the advantageous/favourable traits to their off-spring; Or Variation ensures propagation of desirable/favourable traits; to the future generations/off-spring, ensuring improved/quality population; c) Provides information/advice to individuals/families/communities about genetic disorders; Helps identify/test/advice families/communities on possible risks of genetic disorders; Provides supportive services/serves as patient advocates/refer individuals/families to relevant health professionals; K.C.S.E Biology Q & A - MODEL 2018PP2QN01
The diagram below illustrates a section of the mammalian kidney.
​(a) Name the structures labelled E and F.
E F (b) Explain the processes that take place in the regions labelled G and H. Region G Region H
answers
​ (a) E—Glomerulus;
F — Interlobular artery/branch of renal artery; (b) Region G At the (glomerulus), the afferent arteriole which brings blood to the glomerulus is wider than the efferent arteriole; this creates high pressure; leading to ultrafiltration; At the proximal convoluted tubule /distal convoluted tubule, substances required by the body/amino acid substances required by the body (amino acids/glucose/vitamins! some water; are selectively re-absorbed (into the blood stream); hence selective reabsorption; Region H At the descending arm of/limb of the Loop of Henle, water is selectively reabsorbed; At the ascending arm/limb of the Loop of Henle, sodium ions/salts are actively/selectively reabsorbed; At the collecting duct, water is (selectively) reabsorbed:
K.C.S.E Biology Q & A - MODEL 2017PP2QN08
Describe how the mammalian eye is structurally adapted to its function.
answers
K.C.S.E Biology Q & A - MODEL 2017PP2QN07
Explain the importance of protecting the forest ecosystem with reference to the following:
(a) climate change (b) biodiversity (c) biotechnology (d) water conservation (e) pollution.
answers
a) Climate change
K.C.S.E Biology Q & A - MODEL 2017PP2QN06
In an investigation, two potted plants G and H belonging to the same species were exposed to increasing light intensities at different temperatures, 30°C and 20°C respectively. The rate of photosynthesis was measured for each plant and results recorded as shown in the table below:
​(a) On the same axis, plot graphs of rate of photosynthesis against light intensity for plants G and H.
(b) State the aim of the investigation. (c) Account for the difference in the rate of photosynthesis in the two plants. (d) Account for the difference in the rate of photosynthesis in the two plants between the following light intensities: (i) 1—4 units (ii) 4—8 units. (e) (i) Predict the rate of photosynthesis at light intensity of 16 units. (ii) Give a reason for your answer in (e) (i) above. (f) State one internal and one external factor that could be limiting in the investigation.
answers
b) To investigate/compare the effect of (varying) light intensity/temperature on the rate of photosynthesis;
c) Rate of photosynthesis is higher in plant G (than H); (Photosynthesis being an enzymatic process), enzymes were subjected to favourable/optimal temperatures (of 30°C): hence more activated, unlike in plant H where temperatures were lower (20C); d) (i) 1-4 units Rapid increase in rate of photosynthesis increases with the increase in light intensity; due to increase in light energy for photosynthesis/formation of more ATP molecules; (ii) 4 — 8 units Slower/gradual increase in the rate of photosynthesis as the light intensity increases: because other factors become limiting/some chlorophyll molecules start bleaching; e) i) Slight increase/no significant increase/remains constant; ii) The optimum light intensity has been exceeded/some chlorophyll could be destroyed; f) Internal factor — Chlorophyll/enzyme concentration; External factor — Carbon (IV) oxide concentration/amount of water;
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
State how in-breeding leads to reduced hybrid vigour
answer
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
State two advantages of using genetically modified varieties in bean farming.
answers
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
In beans, the gene for purple colour is dominant over the gene for white colour. A pure breeding bean plant with purple colour was crossed with a heterozygous bean plant.
Using the letter P to represent the gene for purple colour, work out the genotypic ratio of the offspring. Name the hormone responsible for the development of secondary sexual characteristics in human males.1/7/2020
K.C.S.E Biology Q & A - MODEL 2017PP2QN04
Name the hormone responsible for the development of secondary sexual characteristics in human males.
answer
K.C.S.E Biology Q & A - MODEL 2017PP2QN04
State the significance of diploidy.
answers
K.C.S.E Biology Q & A - MODEL 2017PP2QN04
(i) Define the term diploidy.
(ii) Name the type of cell division that gives rise to diploid cells. (iii) Name the type of cells in which the process named in (b) (ii) above Occurs.
answers
​ i. State of being/having two sets of chromosomes and therefore two copies of genes (especially in somatic/body cells);
ii. Mitosis; iii. Body cells/somatic cells;
K.C.S.E Biology Q & A - MODEL 2017PP2QN04
Explain how the sex of a male child is determined in human beings.
answers
K.C.S.E Biology Q & A - MODEL 2017PP2QN03
The diagram below illustrates the appearance of a plant cell after it had been put in a certain solution.
​(a) Explain the appearance of the cell at the end of the treatment.
(b) Explain the results obtained if a red blood cell is subjected to the same treatment. (c) Explain why transfusion with distilled water is not recommended for a dehydrated patient.
answers
​(a) The cell is turgid; its cell sap was hypertonic (compared to the solution in which it was placed); by osmosis, water moved into the cell across its cell semi-permeable membrane, (swelling and becoming turgid);
(b)The red blood cell lacks the cell wall; water molecules move across its semi-permeable membrane by osmosis; into its hypertonic medium (inside the cell),cell contents/cytoplasm swelling and bursting haemolyses; (c)Would haemolyse; due, to lowering of the osmotic pressure of the blood below normal; K.C.S.E Biology Q & A - MODEL 2017PP2QN01
The diagram below represents a nucleus.
​(a) Name the structures labelled E and F.
(i) E F (ii) State the function of F. (iii) With reference to the nucleus, state one difference between an animal and a bacterial cell. (b) Name the plant cell organelle: (i) that stores chlorophyll (ii) responsible for intracellular digestion. (c) State two main functions of the vacuole in the amoeba.
ANSWERS
​(a) E—Nucleolus;
F — Nuclear pore/nucleopore; ii. Facilitates movement of materials in and out of the nucleus; iii. Nuclear material in the bacterial cell is not enclosed within a membrane /prokaryotic, while in animal cell it is enclosed eukaryotic; (b) i. Chloroplast; ii. Lysosome; (c) i. Feeding (food vacuole); ii. Osmoregulation (contractile vacuole); iii. Excretion/removal of wastes; K.C.S.E Biology Q & A - MODEL 2017PP1QN19
The table below shows the percentage concentration of certain substances in blood plasma, glomerular filtrate and urine in a human being at a particular time.
​(a) Explain the likely impact on the composition of urine in case of the following:
(i) Vigorous physical exercises (ii) a meal rich in proteins (b) Name the processes responsible for: (i) Presence of glucose in the glomerular filtrate (ii) absence of glucose in urine
answers
​a. i) Less water and urea; since sorne is excreted/eliminated through the skin (as sweat);
ii) increased amount of urea in the urine; due to deamination of amino acids (from proteins); b. i) ultra filtration; ii) Selective reabsorption;
K.C.S.E Biology Q & A - MODEL 2016PP2QN08
Describe how the mammalian heart is structurally adapted to its function.
answers
K.C.S.E Biology Q & A - MODEL 2016PP2QN07
Using a relevant example in each case, describe simple and conditional reflex actions.
answers
Simple reflex action eg. withdrawal of finger from a sharp object/ hot object; its an automatic response to a specific stimulus; when the finger touches sharp object/ hot object, the pain receptors/ thermoreceptors in the skin are stimulants; and trigger off a nerve impulse; the nerve impulse is transmitted via the senses neurone; to the grey matter of the spinal cord/ CNS/ brain; the impulse is then transmitted via synapse; to the relay neurone; and then through another synapse; to the motor neurone; and then through another synapse; to the motor neurone; the impulse is then transmitted to the effector muscles in the hand; ace - efferent neurone for motor neurone Afferent neurone for sense neurone intermediate/ associative/ connector/interauncial neurone - for relay. The effector muscles/ biceps contract; and the finger is withdrawn from the hot object/ sharp object;
Conditioned reflex action - salivation in a dog/ human being (ace. any other relevant example) student in response to sound; it is an automatic response evoked from an animal by unrelated stimulus; substituted for the one which normally elicits the response; it develops from a past experience; and involves modification of behaviour/involves learning; it weakens with time; and must be reinforced by repeating the related stimulus; the dog/ student salivates when the bell (for meals) rings; because they have learnt to associate the ringing of the bell at meal time with food; everytime it rings (accept use of other relevant examples) they are offered food. K.C.S.E Biology Q & A - MODEL 2016PP2QN06
An experiment was carried out to investigate the effect of temperature on the rate of reaction catalysed by an enzyme. The results are shown in the table below.
​(a) On the grid provided plot the rate of reaction against temperature.
(b) When was the rate of reaction 2.6 mg of product per unit time? (c) Account for the shape of the graph between: (i) 5°C and 40°C (ii) 45°C and 60°C (d) Other than temperature name two ways in which the rate of reaction between 5°C and 40°C could be increased. (e)(i) Name one digestive enzyme in the human body which works best in acidic condition. (ii) how is the acidic condition for the enzyme named in (e) (I) above attained’? (f) The acidic condition in (e) (iii) above is later neutralized. (i) Where does the neutralization take place? (ii) Name the substance responsible for the neutralization.
answers
​(b) 330C and 51.5 (± 0.50C)
32.5 - 33.5 and 51.0 – 52.0 (c) (i) 5°C and 40° C As temperature is increased rate of reaction is increased/ more products are formed (per unit time) because enzymes become more active (ii) 45° C and 60° C As temperature increase rate of reaction decreases less/products are formed (unit per time) because enzymes become denatured by high temperatures above 40, hence cannot act on substrate. (d) Increase in enzyme and substance concentration Use of co-factors and co-enzymes (e) (i) Pepsin, Chymosin Renin (ii) Wall of stomach/ gastric gland/ oxyntic/ pariental/ cell produced Hydrochloric (f) (i) Duodenum (ii) Bile juice/ e.g. NaHCO3 K.C.S.E Biology Q & A - MODEL 2016PP2QN05
A freshly obtained dandelion stem measuring 5cm long was split lengthwise to obtain two similar pieces. The pieces were placed in two different solutions of different concentrations in petri dishes (L1 and L2) for 20 minutes. The appearance after 20 minutes is as shown.
​(a) Account for the appearance of the pieces in solutions L1 and L2
(b) Suite the significance of the biological process involved in the experiment.
answers
(a) L1 - Inner cells gained water by Osmosis; hence increased in length; epidermal cells did not gain water because they are covered by a water proof cuticle leading to curvature.
L2 - Inner cells lost water by osmosis; leading to (flaccidity) decrease in length; epidermal cells did not lose water due to waterproof leading to curvature (b) Absorption of water by the roots Opening and closing of the stomata K.C.S.E Biology Q & A - MODEL 2016PP2QN04
The diagram below represents some gaseous exchange structures in humans.
​(a)Name the structures labeled K, L and M.
(b) How is the structure labeled J suited to its function? (c) Name the process by which inhaled air moves from the structure labeled L into blood capillaries. (d) Give the scientific name of the organism that causes tuberculosis in humans.
ANSWERS
​(a) K- Pleural membranes
L- Alveolus M- Intercostal muscles (b) Has C- shaped cartilage rings that support it preventing it from collapsing and allow free flow of air Inner lining has mucus secreting cells that trap fine dust particles and microorganisms Inner lining has hair like structures called cilia that enhance upward movement of the mucus to the larynx (c) Diffusion (d) Mycobacterium tuberculosis (underline separately). K.C.S.E Biology Q & A - MODEL 2016PP2QN03
The diagram below represents bones at a joint found in the hind limb of a mammal.
​(a) Name the bones labeled X, Y and Z
X Y Z (b) (i) Name the substance fi)und in the place labeled W. (ii) State the function of the substance named in (b) (î) above. (c) Name the structure that joins hones together at the joint. (d) State the difference between ball and socket joint and the one illustrated in the diagram above. (e) Name the structure at the elbow that performs the same function as the patella.
ANSWERS
​(a) X- Femur
Y- Tibia Z- Fibula (b) (i) Synovial fluid (ii) Lubrication of the joint/ shock absorption Distribution of pressure (c) Ligament (d) Ball and socket joint allows movement in all planes while the illustrated allows movement in one plane only. Accept 360 for all planes 180 for one plane (e) Olecranon process |
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