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K.C.S.E Biology Q & A - MODEL 2017PP1QN10
State the effect of movement of the diaphragm muscles during inhalation in mammals.
answers
Give one reason why the coarse adjustment knob should not be used to lower the high power objective.30/6/2020
K.C.S.E Biology Q & A - MODEL 2017PP1QN09
Give one reason why the coarse adjustment knob should not be used to lower the high power objective.
answers
K.C.S.E Biology Q & A - MODEL 2017PP1QN09
State the function of a mirror in a light microscope.
answers
K.C.S.E Biology Q & A - MODEL 2017PP1QN08
Explain why short distance runners breathe quickly and deeply at the end of a race.
answers
K.C.S.E Biology Q & A - MODEL 2017PP1QN07
The diagram below represents a stage in the division of a cell.
​With a reason, identify the organism from which the cell was obtained.
answers
K.C.S.E Biology Q & A - MODEL 2017PP1QN06
Name two enzymes in the human digestive system which are secreted in an inactive form.
answers
K.C.S.E Biology Q & A - MODEL 2017PP1QN05
The photograph illustrates a housefly at various stages of its development.
​(a) (i) On the photograph, name the stages of the life cycle.
(ii) Using arrows, link the stages of the life cycle in the correct order. (b) (i) State two differences between the life cycles of a housefly and that of a cockroach. (ii) State one advantage of the life cycle of a cockroach to itself.
answers
(ii)Absence of larva and pupa shortens the life cycle of the organism; (avoiding adverse/extreme environmental conditions that would affect its growth/general life processes);
K.C.S.E Biology Q & A - MODEL 2017PP1QN04
In an experiment on respiration, a mouse was observed to have inhaled 200 cm3 of oxygen and exhaled 199.75 cm3 of carbon(IV) oxide in ten minutes.
​(a) Calculate the respiratory quotient for the activity in the experiment.
(b) Identify the possible food substance consumed by the mouse. (c) State the fate of the excess food named in (b) above in the human body.
answers
b) Carbohydrates/glucose;
c) Stored in the body as fat/subcutaneous deposit/adipose tissue; Stored as glycogen (in the liver / muscle cells); (Increase) oxidation; K.C.S.E Biology Q & A - MODEL 2017PP1QN03
During a practical investigation on food tests, students were provided with the following reagents.
Benedict’s solution Sodium hydrogen carbonate Dilute hydrochloric acid.
​(a)Identify the food substance the students were to test.
(b) State the role of dilute hydrochloric acid and sodium hydrogen carbonate during the experiment. (i) Dilute hydrochloric acid (ii) Sodium hydrogen carbonate
answers
​a) Non reducing sugar;
b) (i) Hydrolyze/break down sucrose! non reducing sugars to reducing sugars/glucose/fructose; (ii) neutralize the acid; K.C.S.E Biology Q & A - MODEL 2017PP1QN02
Below are diagrams of a cell organelle obtained from different organs of an animal
​(a) (i) For each organelle state an organ in the urinary system where it is likely to be found.
F G (ii) Give a reason for your answers in (a) (i) on page 2. (b) Name the part of the chloroplast where the following reactions occur: (i) Carbon(IV) oxide fixation (ii) Photolysis
answers
(a) (i) F - Kidney;
G - Bladder/Ureter/Urethra; ii) Kidney - active re-absorption of solutes requires more energy; organelle F has more cristae for attachment of more respiratory enzymes producing more energy; Bladder/ureter/urethra does not require as much energy/organelle G has less number of cristae hence fewer respiratory enzymes attached/less energy produced; (b) i) Stroma; ii) Grana/granurn; K.C.S.E Biology Q & A - MODEL 2017PP1QN01
Below is an illustration of a piece of apparatus strategically positioned to trap some organisms.
​(a) Name the apparatus.
(b) State the function of the part labelled E.
answers
​a) Pooter/Aspirator;
b) To prevent dirt/insects from entering the suction tube/into the mouth;
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 |
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