K.C.S.E Biology Q & A - MODEL 2011PP2QN06
An experiment was carried out to investigate the population of a certain micro-organism. Two petri-dishes were used. Into the petri-dish label led M, 60cm3 of a culture medium was placed while 30cm3 of the same culture medium was placed in petri-dish labelled N. Equal numbers of the micro-organisms were introduced in both petri-dishes. The set-ups were then incubated at 35°C. The number of micro-organisms in each petri-dish was determined at irregular intervals for a period of 60 hours. The results were as shown in the table below.
(i)On the same axes, draw the graphs of relative number of micro-organisms against time on the grid provided.
(ii) After how many hours was the difference between the two populations greatest? (iii) Work out the difference between the two populations at 50 hours. (iv) With a reason state the effect on the population of micro-organisms in petri-dish M if the temperature was raised to 60°C after 20 hours. (v) Account for the shape of the curve for population in petri-dish N between 46 hours and 59 hours.
answers
​(ii) 42 hours;
(iii) Graph M at 50 hrs is 1220 ± 20. Graph N at 50 hrs is 540 ± 20 (2 m 1220-540=680±4; (iv) Population growth stops; . High temperatures kill the microorganisms/denature enzymes; (v) 46 hours to 59 hours death rate of the microorganisms is higher, than their population growth rate; due to exhaustion of nutrients; and accumulation of toxic wastes;
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K.C.S.E Biology Q & A - MODEL 2011PP2QN05
The diagram below represents a flower.
(i) On the diagram, name two structures where meiosis occurs.
(ii) How is the flower adapted to prevent self-pollination? (ii) How is the flower adapted to prevent self-pollination? (b) The diagram below represents a human reproductive organ.
​(i) Explain two adaptations of the structure labelled L to its functions.
(ii) Explain the role of the gland labelled K.
answers
​(a) (i) Anthers; Ovary;
(ii) Anthers are below the stigma to minimise self pollination;
production; it has many, long and coiled seminiferous tubules to increase the surface area for production/storage of sperms; (ii) K produces an alkaline fluid that neutralizes acid in the vagina; this fluid contain nutrients for the sperms; and also activates sperms; K.C.S.E Biology Q & A - MODEL 2011PP2QN04
The diagram below represents a section of the human brain.
(i)Name the structures labelled P and R.
P R (ii) State two functions of the part labelled Q. (b) (i) Name two reproductive hormones secreted by the pituitary gland in women. (ii) State one function of each of the hormones named in (b)(i) above.
answers
(a) (i) - is cerebral hemisphere/cerebrum;
R - medulla oblongata; (ii) Muscular co-ordination; maintaining body posture; manual/motar dexterity; (b) (i) Follicle stimulation hormone; luteinizing hormone; oxytocin; prolactin; (ii) FSH - stimulates secretion of oestrogen; stimulates development of the Graafìan follicle; LH - Brings about ovulation; causes development of corpus luteum; Oxytocin - causes contraction of uterus; causes expulsion of milk from mammary glands; Prolactin - stimulates milk production/secretion;
K.C.S.E Biology Q & A - MODEL 2011PP2QN03
How are the pneumatophores adapted to their function?
answers
K.C.S.E Biology Q & A - MODEL 2011PP2QN03
Describe how oxygen in the alveolus reaches the red blood cells.
answers
K.C.S.E Biology Q & A - MODEL 2011PP2QN03
Name the causative agents for the following respiratory diseases.
(i) Whooping cough. (ii) Pneumonia.
answers
(a) (i) Bordetella pertussis;
(ii) Streptococcus pneumoniae; (iii) Micoplasma pneumoniae;
K.C.S.E Biology Q & A - MODEL 2011PP2QN02
Explain how comparative embryology is an evidence for organic evolution.
answer
K.C.S.E Biology Q & A - MODEL 2011PP2QN02
Name two disorders in humans that are determined by sex-linked genes.
answers
K.C.S.E Biology Q & A - MODEL 2011PP2QN02
In humans, hairy ears is controlled by a gene on the Y Chromosome.
(a) Using letter Y^H to represent the chromosome carrying the gene for hairy ears, work out a cross between a hairy eared man and his wife. (b) (i) What is the probability of the girls having hairy ears? (ii) Give a reason for your answer in (b(i) above. K.C.S.E Biology Q & A - MODEL 2011PP2QN01
The set-up below illustrates a procedure that was carried out in the laboratory with a leaf plucked from a green plant that had been growing in sunlight.
(i) What was the purpose of the above procedure?
(ii) Give reasons for carrying out steps A, B and C in this procedure. A B C (iii) Name the reagent that was used at the step labelled D. (iv) State the expected result on the leaf after adding the reagent named in (iii) above.
ANSWERS
​(i) - Testing a leaf for the presence of starch;
(ii) - A - kill the leaf/break down cells/stop enzymatic activity; B - Removal of chlorophyll; C - Soften leaf/makes leaf less brittle; (iii) Iodine solution; (iv) Areas where starch is present stain blue/blue black; K.C.S.E Biology Q & A - MODEL 2011PP1QN14
The diagram below represents a certain plant.
​(a) What is the likely habitat for the plant?
(b) Give two reasons for your answer in (a) above.
answers
​(a) Dry/Arid/Semi-arid/Desert;
(b) Succulent/ fleshy stem; reduced leaves/leaves reduced into thorns/leaves modified into spines/spikes;
K.C.S.E Biology Q & A - MODEL 2010PP2QN08
Describe how a finned fish such as Tilapia moves in water.
answers
​Movement of fish in water is by swimming; It involves forward movement and control of the body position in water; Scales overlapping backwards/mucus/streamlined body shape reduces resistance/friction to enhance forward movement; Forward movement (propulsion) is caused by the tail; The tail is (almost half the length of the body of the fish) to enable it create enough force (to enable the fish to push forward);
Propulsion is achieved when the tail pushes sideways against the water; Sideways movements is brought about by muscles arranged in segmented blocks/myotomes on both sides of vertebral column; The muscles contract alternately causing the vertebral column to swing sideways; When muscle blocks on the right relax and those on the left contract; the body bends to the left side; When the muscles of the left relax and those on the right contract; the body bends to the right; The fish uses its fins to control the position of its body in water, During forward movement paired fins/pectoral and pelvic fins lie flat on the body surface to reduce resistance/friction; To change direction the fish uses the paired fins; Paired fins are also used by fish to change its level in water/control/prevent pitching; The fish spreads out the pectoral and pelvic fins at 90 degree to the body; to enable it to brake; Fish can also use the swim bladder to change its level in water; When the bladder fills up with air the fish becomes lighter/more buoyant; making it to rise in water; When the air leaves the bladder the fish becomes heavier; making it to sink deeper in the water; water currents may cause the sideways swaying of the body of the fish! yawing; Dorsal and ventral fins prevent rolling/yawing;
K.C.S.E Biology Q & A - MODEL 2010PP2QN07
Describe die process of fertilization in flowering plants.
answers
​Pollen grains land onto the stigma; and adhere to it as a result of the stigma cells secreting a sticky substance; It absorbs nutrients; and germinates forming a pollen tube; The pollen tube grows down the style to the ovary; deriving nourishment from surrounding tissues; The pollen tube has tube nucleus at the tip; and generative nucleus immediately behind it; As the tube grows downwards into the ovary the generative nucleus divides mitotically; to give rise to two nuclei; which represent the male gametes; The pollen tube penetrates the ovule/embryo sac through the micropyle/chalazza; After the pollen tube enters the embryo sac, the tube/vegetative nucleus breaks down; leaving a clear passage for the entry of the male nuclei;
which enter the embryo sac; where one fuses with the egg cell nucleus; to form a diploid zygote; which develops into an embryo; The other male nucleus fuses with the two polar nuclei; to form a triploid nucleus/primary endosperm nucleus; Which becomes endosperm; This type of fertilization is called double fertilization; K.C.S.E Biology Q & A - MODEL 2010PP2QN06
In an experiment to investigate a certain physiological process, a boiling tube labelled A and a test tube labelled B were covered with cotton wool. The two tubes were simultaneously filled with hot water and fitted with thermometers. The experimental set-up was as in the diagrams below.
​Temperature readings were taken at the start and after every two minutes for twenty minutes. The results were as shown in the table below.
(a) Using the same axes, draw graphs of temperature against time.
(b) (i) Work out the rate of heat loss in the boiling tube labelled A and test-tube labelled B between the 5th and 15th minutes. A B (ii) Account for the answers in (b) (i) above. (iii) How does the explanation in (b) (ii) above apply to an elephant and a rat? (c) (i) State the role of the cotton wool in this experiment. , (ii) Name two structures in mammals that play the role stated in (c) (i) above. (d) State three advantages of having constant body temperature in mammals.
ANSWERS
(b) (i) A: 56—48.5 7.5C
7.5C/10 Minutes ; = 0.75C Per Minute; ±0.05 B: 48-34=14C 14C/10 Minutes ; =1.4C Per Minute; ±0.05 (ii) B has a larger surface area to volume ratio; making it to lose heat to the surrounding faster; (the converse is true) (iii) A rat has larger surface area to volume ratio compared to an elephant; making the rat to lose heat at a faster rate than an elephant; (c)(i) Insulation/insulate against heat loss; (to surrounding); (ii) Subcutaneous fat layer / adipose tissue; Fur / hair; . (d) Are active always; (even under very cold conditions) Are able to escape from predators/search for mates/food; (because they are active always) Can survive in a wide variety of habitats: (both cold and hot) K.C.S.E Biology Q & A - MODEL 2010PP2QN05
When pure breeding black guinea pigs were crossed with pure breeding white guinea pigs, the offspring had a coat with black and white patches.
(a) Using letter G to represent the gene for black coat colour and letter H for white coat colour, work out the genotypic ratio of F2. (b) State the phenotypic ratio of F2. (c) (i) Name the term used when two alleles in heterozygous state are fully expressed phenotypically in an organism. (ii) Give an example of a trait in human beings where the condition whose term is named in (c) (i) above expresses itself. K.C.S.E Biology Q & A - MODEL 2010PP2QN03
The diagram below represents a food web in a certain ecosystem.
(a) Name the trophic level occupied by each of the following:
(î) caterpillars; (ii) small insects. (b) From the food web, construct two food chains which end with lizards as a tertiary consumer. (e) (i) Which organisms have the least biomass in this ecosystem? (ii) Explain the answer in (c) (1) above.
ANSWERS
​(a) (i) Primary consumers;
(ii) Primary/secondary consumers; (b) Green plants — Caterpillars — Lizards; Decaying leaves —Caterpillars — small insects — Lizards; (e) (i) Hawks; (ii) At each trophic level energy is lost as heat in respiration; and during decomposition; lost in defecation/faeces/ waste products or metabolism/excretion; some parts of organism not eaten e.g. feathers; K.C.S.E Biology Q & A - MODEL 2010PP2QN02
The diagram below shows blood circulation in a mammalian tissue.
(a) Name the parts labelled P and Q.
P . Q . (b) Name the substances that are: (i) required for respiration that move out of capillaries; (ii) removed from tissue cells as a result of respiration. (e) Explain how substances move from blood capillaries into the tissue cells. (d) Name one component of the blood that is not found in the part labelled P.
answers
(a)
P Tissue fluid/intercellular/interstitial fluid/space; Q Venule; (b) (i) Glucose, oxygen; (ii) Carbon (iv) Oxide, water; (c) Blood entering arteriole has a high pressure; the pressure forces water and small solute molecules in blood to go through capillary wall forming tissue fluids; nutrients/oxygen more into the tissue cells by diffusion; (d) Red Blood cells/proteins/platelets; K.C.S.E Biology Q & A - MODEL 2010PP2QN01
In an experiment, disinfected soaked bean seeds were put in a vacuum flask which was then fitted with a thermometer as shown in the diagram below.
The temperature readings were taken every morning for three consecutive days.
(a) Which process was being investigated? (b) (i) What were the expected results? (ii) Account for the answer in (b)(i) above, (c) Why were the seeds disinfected? (d) Why was a vacuum flask used in the set-up? (e) How would a control for this experiment be set?
answers
(a) Respiration;
(b) (i) Increase/rise in thermometer reading/temperature; (ii) Carbohydrates/starch/glucose in germinating seeds is broken down/oxidised to get energy; some of the energy is released as heat; (which increases temperature reading). (c) To kill bacteria/fungi/microorganisms; that would cause decay/decomposition/respiration of the beans; (d) To conserve heat/prevent heat loss to surroundings; (e) Use similar set-up but with dead and disinfected beans seeds/ use dead disinfected bean seeds/use dry bean seeds;
K.C.S.E Biology Q & A - MODEL 2009PP2QN08
Describe the role of the liver in homeostasis in the human body
answers
K.C.S.E Biology Q & A - MODEL 2009PP2QN07
How are flowers adapted to wind and insect pollination?
answers
K.C.S.E Biology Q & A - MODEL 2009PP2QN06
An experiment was carried out to investigate the effect of temperature on the rate of reaction catalyzed by an enzyme. The results are shown in the table below
(a)On t he grid provided draw a graph of 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 60C (d) Other than temperature name two ways in which the rate of reaction between 5C and 40C could be increased (e) (i) Name one digestive enzymes 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 conditions in (e) (ii) above is later neutralized (i) Where does the neutralization take place? (ii) Name the substance responsible for neutralization
answers
​(b) 33C and 51.5 ( ± 0.5C)
32.5 - 33.5 and 51.0 – 52.0 (c)(i) As temperature is increased rate of reaction is increased/ more products are formed (per unit time) because enzymes become more active (ii) As temperatures increases rate of reaction decreases less products are formed (unit per time) because enzymes become denatured by high temperatures. (b) Increase in enzyme concentration and substance concentration Increasing number of enzyme (e) (i) Pepsin, remain/ chymosin (ii) Wall of stomach/ gastric gland/ oxyntic/ pariental/ cell produced Hydrochloric (f) (i) Duodenum (ii) Bile juice/ SANS any correct salt e.g. NaHCO3
K.C.S.E Biology Q & A - MODEL 2009PP2QN05
Give three functions of pectoral and pelvic fins in a fish
answers
​ - Steering
- Balance - Braking, changing direction - Prevent fish from pitching/ up & down movement K.C.S.E Biology Q & A - MODEL 2009PP2QN05
Name a support tissue in plants thickened with
(i) Cellulose (ii) Lignin
answers
(i) Collencyma
(ii) Xylem/ tracheid/ vessels/ schlerencyma
K.C.S.E Biology Q & A - MODEL 2009PP2QN05
what happens when a wilting young plants is well watered
answers
K.C.S.E Biology Q & A - MODEL 2009PP2QN04
(a) (i) Explain the changes that take place in the pupil and iris of a human eye when a person moves from a dark room to a room with bright light
(ii) What is the significance of the changes explained in (a) above (b) How does the human eye obtain nutrients? (c) Explain why images that form on the blind spot are not perceived
answers
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