K.C.S.E Biology Q & A - MODEL 2019PP1QN13
A female human being was found to have an extra sex chromosome in her cells.
​(a) Give the total number of chromosomes in the female individual’s cells.
(b) Explain the possible cause of this condition. (c) State two physical characteristics observed in the female individual with such a condition.
answers
(a) 47
(b)Non-disjunction/failure of homologous chromosome to separate/segregate (in anaphase I) or failure of sister chromosome to separate/segregate (in anaphase II); resulting in an extra X sex chromosome, X chromosome in a cell having XXX instead of XX; (c) infertile / ovary abnormalities; Taller than average female; Development delays; (more pronounced) signs of obesity; Flat feet Abnormally curved fingers; Widely spaced eyes; Abnormally shaped breast bone;
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K.C.S.E Biology Q & A - MODEL 2019PP1QN12
While investigating a certain metabolic process in plants, students set up the apparatus as shown be low in a classroom and monitored it for 48 hours.
​(a) Identify the metabolic process under investigation.
(b) Account for the observations made in the test tube at the end of the investigation.
answers
K.C.S.E Biology Q & A - MODEL 2019PP1QN11
Explain each of the following physiological observations:
(a) sportsmen release little, concentrated urine at the end of a strenuous exercise (b) a rabbit has a higher oxygen demand than a camel
answers
​(a) during /after the exercise one sweat ; (profusely to cool the body/eliminate some nitrogenous (wastes) a lot of water is lost through this ; one is dehydrated ;(the little) water that is left in the body system (further) selectively reabsorbed in the kidney tubules (resulting in less but concentrated urine;)
(b) a rabbit has a higher surface area to volume ratio/ smaller in size hence has a bigger surface area exposed to heat loss to the environment/ lose heat faster/ its more active than the camel; hence need more oxygen to(aerobically) respire (to synthesize the needed energy to support its activity /lifestyle; K.C.S.E Biology Q & A - MODEL 2019PP1QN10
In an investigation, students set up the apparatus below in the laboratory and made observations after 72 hours.
​(a) Explain how inclusion of the following components would affect the mouse in the experiment:
(i) light (ii) sodium hydroxide solution (b) State why the students preferred to use a bell jar and not a tin box in the experiment.
answers
​.(a) i) light enables the potted plant to photosynthesize; producing oxygen which is
Inhaled by the mouse, (sustaining it); the illuminated light can further affect /alter some photosynthesized processes in the mouse as a result of constant direct beam of light. (ii) Absorbs carbon(iv)oxide (mainly exhaled by the mouse); while at the same time deny the plant the needed raw material, carbon (iv) oxide to photosynthesize hence suffocating the mouse/ emitting its survival / no oxygen; (b) bell jar is transparent, allow penetration of light for the plant to photosynthesize; tin box is opaque hence does not allow photosynthesis/ could easily heat up altering the temperature inside for the mouse/ plant; K.C.S.E Biology Q & A - MODEL 2019PP1QN09
Below is a photograph of Brassica oleracea, Sukuma wiki leaf.
​(a)State two observable features that adapt the leaf to gaseous exchange.
(b) Explain the relationship between photosynthesis and aerobic respiration within the leaf.
answers
​.(a) broad leaf blade /lamina; that expose more stomata for gaseous exchange; acc broad leaf alone
(b) photosynthesis (within the leaf in the presence of light energy) yield simple carbohydrates /glucose /sugars which form the main substrate during aerobic respiration (producing energy (ATP) During the process of respiration carbon iv oxide produced is intern used as a raw material in photosynthesis; During photosynthesis water is broken down yielding oxygen which is needed/ used in (cellular) (aerobic respiration); K.C.S.E Biology Q & A - MODEL 2019PP1QN08
State the role of each of the following in the mammalian respiratory system:
(a) mucus (b) cartilage rings (c) epiglottis
answers
.(a) trap foreign particles (from the inhaled /entering air); moisten the (inhaled/incoming) air (for efficient gaseous exchange);
(b) keep the wind pipe /trachea open / not to collapse (to allow for continuous flow of air); (c) acts as a valve / flap between the larynx and the oesophagus to permit air to enter the air way to the lungs and food particles to pass into the gut / oesophagus: acc prevent food particles from entering the trachea /air passage during swallowing;
K.C.S.E Biology Q & A - MODEL 2019PP1QN07
Distinguish between chemical and mechanical digestion.
answers
K.C.S.E Biology Q & A - MODEL 2019PP1QN06
​(a) Name the respiratory structure in the amoeba.
(b) Give a reason for your answer in (a) above.
answers
(a) cell membrane/plasma membrane /plasmalemma;
(b) has a large surface area to volume ratio
K.C.S.E Biology Q & A - MODEL 2019PP1QN05
Explain why significantly increasing the blood pH slows down the rate of selective reabsorption of materials in the kidney tubules.
answers
K.C.S.E Biology Q & A - MODEL 2019PP1QN04
In investigating a certain physiological process, students set up the apparatus as shown below and made the observations after 30 minutes as illustrated.
​(a) Name the physiological process being investigated.
(b) Account for the observation made at the end of the experiment. (c) State the likely identity of G.
answers
. (a) osmosis
(b) solution E is hypertonic/ had more solute molecules compared to solution F; solution F hypotonic to solution E; by osmosis water molecules move through the semi- permeable membrane G (from solution F to E); hence decreases in volume of F/ increased solution E; (c) semi permeable membrane /visking tubing /slice of potato /pawpaw (any other permeable plant tissue) pig bladder/cellophane paper/dialysis membranes. K.C.S.E Biology Q & A - MODEL 2019PP1QN03
The diagram below illustrates a specialised cell obtained from a certain tissue.
​(a) Name the cell.
(b) State two ways in which the cell is structurally adapted to its function.
answers
(a) nerve cell/motor neuron; acc neuron
(b) longer axon to transmit impulses/delivers action potential along way; has numerous dendrites for receiving/delivering /transmitting impulse; myelin sheath for faster transmission of impulse/insulation of axon; Schwan cell for secretion of myelin sheath; node of ranvier to enhance speed of transmission of impulse; cell body has nucleus for controlling nerve impulse transmission.
K.C.S.E Biology Q & A - MODEL 2019PP1QN02
Explain why the bat is classified as a mammal yet it flies.
answers
K.C.S.E Biology Q & A - MODEL 2019PP1QN02
Besides venation, state two other external characteristics of leaves that can be used to classify plants.
answers
(a) shape of the leaf blade/lamina(broadness or narrowness); leaf margin(smooth or serrated); leaf apex(pinnate dot rounded);leaf arrangement; leaf colour ; (leaf texture(smooth or rough); leaf type(simple or compound)leaf sheath/petiole(absence or presence)
(b) has mammary gland; body covered with fur/hair; gives birth/does not lay eggs; has external ears/pinnae; has seven cervical vertebrae; has sweat glands; heterodonts/four types of teeth K.C.S.E Biology Q & A - MODEL 2019PP1QN01
Name the characteristic of living organisms illustrated by each of the activities described below:
(a) Dressing heavily (b) Bursting of the sporangium in the Rhizopus sp
answers
K.C.S.E Biology Q & A - MODEL 2018PP2QN08
Describe what happens to a meal rich in proteins along the alimentary canal from ingestion to egestion.
answers
​The meal is ingested through the mouth; (In the mouth), it is chewed/masticated (by teeth); to reduce/break it into smaller particles; mixed with saliva (from salivary gland);
The food is then rolled (by the tongue) into boluses; and pushed down into the oesophaghus/swallowed; The boluses move by peristalsis (into the stomach); Constant contractions/relaxations of the stomach walls mix the food, (giving rise to chime); Presence of food in the stomach further stimulates production of gastric juice; which contains pepsinogen; and rennin/chymosin; Pepsinogen is activated to pepsin; by hydrochloric acid; (contained in the gastric juice). Pepsin breaks down proteins to peptides; Rennin converts/coagulates the protein, caseinogen; in milk to casein; (which is abundant in young children). It is then pushed into the duodenum (through the pyloric sphincter); Pancreatic juice in the duodenum contains trypsin; which digests proteins into peptides; (secreted in an inactive form, trypsinogen) In the ileum, intestinal juice/Succus enfericus is secreted; It contains peptidase enzymes; which breaks down polypeptides into amino acids; It also contains polypeptidase enzyme; which breaks down peptides to amino acids,completing the process of digestion of the proteins; The amino acids are absorbed into the bloodstream/pass through the epithelia of the villi, and the capillary walls into the blood-stream; by active transport; The undigested/indigestible proteins/food substances pass through to the colon/large intestines; where water is absorbed; leaving a semi-solid waste material being passed on to the rectum; then out through the anus (as faeces);
K.C.S.E Biology Q & A - MODEL 2018PP2QN07
Describe the role of hormones in the human menstrual cycle.
answers
​After/at the onset of menstruation, (the anterior lobe of) the pituitary gland; secretes follicle stimulating hormone (FSH); the FSH causes the Graafian follicle; to develop into the ovary; and stimulate the ovary tissues to secrete oestrogen hormone; Oestrogen brings about repair/healing of the endometrium/uterine wall; its concentration increases to a level which stimulates the (anterior) pituitary gland; to secrete lutenizing hormone (L.H.) and stops further secretion of FSH;
The L.H. stimulates the maturation of the Graafian follicle; LH also stimulates the Graafian follicle to release an ovum into the (funnel of the) fallopian tube/causes ovulation; it also stimulates the remains of the Graafian follicle to form a yellow body/corpus luteum (in the ovary; The corpus luteum is stimulated by the L.H. to produce progesterone; Progesterone then stimulates the thickening of the endometrium/inner lining of the uterine wall; in readiness for implantation; as progesterone level increases, it inhibits (the pituitary gland) from secreting FSH; further increase in progesterone level inhibits the pituitary gland from secreting L.H. This causes the corpus Luteum to degenerate; this reduces the amount of progesterone; the sudden drop in secretion of progesterone causes the endometrium to slough off/menstruation occurs; and the cycle is repeated;
K.C.S.E Biology Q & A - MODEL 2018PP2QN07
Describe the mode of reproduction in a named fungus.
answers
Rhizopus/mucor/mould; reproduce asexually; by sporulation; spores develop from a single cell forming sporangium; which bursts on maturity releasing spores; which are dispersed by air currents/wind germinating; to form new generation/ form a mycelium (if it lands on a suitable medium); Or
Yeast/Saccharomyces/Schizosaccharomyces; reproduce asexually;by budding; parent cell forms an outgrowth/projection/bud; this is followed by division of the nucleus into two; one of the nuclei moves into the bud; which grows and develops into a new cell; 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; 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 2018PP1QN27
Below is a graphical representation of how basal metabolic rates compare in Various animals.
​From the graph, explain why the mouse has a higher breathing rate than the elephant.
answers
K.C.S.E Biology Q & A - MODEL 2018PP1QN26
State two advantages terrestrial animals have in excreting urea as their main nitrogenous waste product.
answers
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