K.C.S.E Biology Q & A - MODEL 2019PP2QN05
A person accidentally touches a hot pan and responds as illustrated in the diagram below.
(a) Explain how the response illustrated above occurs.
(b) Explain how auxins are utilised as selective weed killers in agriculture.
answers
K.C.S.E Biology Q & A - MODEL 2019PP2QN04
In cats, the gene for fur colour is sex-linked. Letter G represents the gene for ginger fur colour while letter B represents the gene for black fur colour in a given cat species. These genes are co-dominant. Heterozygous females have ginger and black patches of fur and their phenotype is described as tortoise-shell.
​(a) With reference to the information given above, what is meant by the term co-dominance?
(b) Explain why male cats with a tortoise-shell phenotype do not usually occur. (c) A tortoise-shell female was crossed with a black male. Determine the genotypes and phenotypes of the offspring.
answers
K.C.S.E Biology Q & A - MODEL 2019PP2QN03
In an experiment, students treated seedlings as illustrated below.
​(i) Account for the observations made in seedling I.
(ii) Explain the similarity in the end results made in seedlings II and III. (iii) State the likely treatment that would make seedlings II and III respond like seedling I.
answers
​(i) Positive phototropism/tip bends towards light; light causes migration of auxins (produced at the tip) to the darker sides; (of the shoot) resulting in faster division of cells/ elongation/growth on the darker /opposite side of the shoot hence bending towards light
(ii) both seedlings remain upright; ( erect) seedling II does not have tip while seedling III the tip has been covered by opaque material preventing light causing unequal distribution of auxins; . uniform/even distribution of auxins) (iii) Fitting a gar block treated with auxins at the decapitated end of seedling II; Removing the opaque material covering the tip of seedling III/ replacing the opaque cap with a transparent one;
K.C.S.E Biology Q & A - MODEL 2019PP2QN03
State one importance of irritability to living organisms.
answers
​(a) Enable living organisms to avoid dangerous/harmful/hash climatic environmental conditions; Enable living organisms obtain/access favourable environmental conditions (light, water, oxygen,
K.C.S.E Biology Q & A - MODEL 2019PP2QN02
The table below shows results of blood cell counts per mm3 of blood from a sample of people living at different altitudes.
​(a) Explain the relationship between:
(i) red blood cells count and the altitude; (ii) white blood cells count and the altitude. (b) Explain why chances of nose-bleeding increase with altitude in humans.
answers
(a) i) Number of red blood cells increase with altitude; to increase oxygen carrying capacity (by haemoglobin molecules in blood); since oxygen concentration is lower at higher altitude;
ii) white blood cells serve to protect the body against harmful microorganisms/pathogens; thernadites of pathogen of the body to microbial attack is not dependent on the altitude (to be countered by the white blood cell); hence 6 the number of white blood cell count is constant at whatever altitude; (b) Atmospheric Pressure decreases with the increase in altitude; the imbalance between the (outer) atmospheric pressure at high altitude and the internal blood pressure (generated by the heart) results in (one) nose bleeding at high altitudes/ internal blood pressure is higher than the (outer) atmospheric pressure. K.C.S.E Biology Q & A - MODEL 2019PP2QN01
In an experiment to investigate the effect of sodium chloride on the growth rate in a spinach seedling, seeds were treated with different concentrations of sodium chloride. The results are as recorded in the table below.
​(a) From the results in the table above, explain the effect of increasing the concentration of sodium chloride.
(b) Apart from a ruler, state two other equipment one would need to determine the rate of growth in the roots. (c) With a reason, state one other part of the seedling the students would focus on to determine the effect of sodium chloride on growth. (d) State the likely effect on the seedling of increasing the concentration of sodium chloride to 2.20mol/l
answers
​(a) Increased Nacl concentration/having more Nacl ions decreases water potential/decrease osmotic potential/ increase osmotic pressure/makes water potential more negative outside the seed/seedling in the surrounding solution to be hypertonic to the cell sap in the seedling ; seeds cells take in water by osmosis) are dehydrated/lose water molecules to the surrounding solution , reducing the growth enzyme activity; have reduced growth rates;
(b) Threads(wire/string) Books; Pen; Marker (pen); Dye/water proof ink/ bloating paper/tissue paper (c) Rate of growth/ increase in length of shoot tip/apex it is a region of (active) cell division/growth (d) The seedling will be (dehydrated) /lose water (hence) wither/die/dry 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 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.
answer
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
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