K.C.S.E Biology Q & A - MODEL 2016PP2QN02
Differentiate between sickle cell anaemia and sickle cell trait.
ANSWERS
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K.C.S.E Biology Q & A - MODEL 2016PP2QN02
How is sex determined in man?
ANSWERS
K.C.S.E Biology Q & A - MODEL 2016PP2QN01
The diagram below represents a human foetus in a uterus.
​(a) Name the part labeled S.
(b) (i) Name the types of blood vessels found in the structure labaled Q. (ii) State the difference in composition of blood found in the vessels named in (b) (i) above. c)Name two features that enable the structure labeled P to carry out its function. (d) State the role of the part labeled R.
ANSWERS
Explain why it is not advisable to be in a poorly ventilated room with a burning charcoal stove.30/6/2020
K.C.S.E Biology Q & A - MODEL 2016PP1QN019
Explain why it is not advisable to be in a poorly ventilated room with a burning charcoal stove.
answer
​Charcoal in limited supply of air produces carbon(ii) oxide, which combines with haemoglobin forming Carboxylhaemoglobin which is a stable compound and does not dissociate easily, reducing capacity of the haemoglobin to carry oxygen leading to suffocation hence death
K.C.S.E Biology Q & A - MODEL 2015PP2QN08
How is a mammalian heart structurally adapted to its function?
ANSWERS
K.C.S.E Biology Q & A - MODEL 2015PP2QN07
Explain the various ways in which seeds and fruits are adapted to dispersal.
ANSWERS
Wind - dispersed seeds / fruits are light / small to be carried by air currents;
Some seeds / fruits have developed hairy structure feather-like projections; wing like structure which increase their surface area to be blown about /carried away by wind; open capsules; borne on long stalks, which are swayed by wind scattering seeds. Water - dispersed fruits / seeds are also light; to float on water; Some, (like coconuts) have fibrous /spongy mesocarps to trap air; making them buoyant/floating on water; Others (like the water lily) produce seeds whose seed coats trap air bubbles; making them float on water; Some have water-proof seed testa / pericarp; remain afloat without soaking /sinking immediately they are released from parent plants; Animal - dispersed fruits have developed hooks; to stick on (the fur of passing) animals; In some cases, fruits are succulent, brightly coloured / scented; to attract animals, birds; The seed coats (of some seeds) are hard; and resistant to the digestive enzymes; hence passing out through the gut undigested; Self dispersal by explosive mechanism; Fruits have sutures/lines of weakness; which split open when drying scattering seeds. K.C.S.E Biology Q & A - MODEL 2015PP2QN06
The graph below shows the relative numbers of three main species of organisms in a pond.
​(a) Giving a reason for your answer, which of the species is a
(i) producer? Reason (ii) secondary consumer? Reason (b) State the depths at which each of the populations labelled L, M and N is at its optimum. L M N (c) (i) Which method may have been used to determine the population of organisms labelled N in the pond? (ii) Give a reason for your answer in (c) (j) above. (iii) State the assumptions made when using the method in (c) (i) above. (d) State two reasons why primary productivity in the pond decreases with depth. (e) Explain the ecological importance of fungi to plants. (f) Why is flooding likely to lead to a cholera outbreak?
ANSWERS
​(a) (i) Producer - M
Reason Largest in number hence source of food for the other species Abundant on the water surface to trap light for photosynthesis; (ii) Secondary consumer - N Reason - Smaller in number than L and M (b) L -1.125m; M- 0.75m; N- 2.00m; (c) (i) Capture - Recapture (method) /Capture - mark - release - recapture; (ii) Animals are highly mobile; (iii) No migration during the period of survey/study; No deaths/variation/reproductiori in population during the period; Method of marking does not affect the animal behaviour; Marked/released animals will freely mix with others in the pond; Released/marked animals will have enough time to mix with the others; There is uniform/random distribution of animals within the period. (d) Decrease in light intensity as depth increases; Decrease in temperature as depth increases; (e) Breakdown of organic materials/decompose/rot/decay of materials; to release plant nutrients; (f) Flood water may mix with human waste contaminated with cholera bacteria; The flood water may then contaminate food / water sources; The contaminated water/food causes cholera infection when ingested; K.C.S.E Biology Q & A - MODEL 2015PP2QN05
In an experiment to investigate a plant response, the set up shown in the diagram below was used.
(a) Name the type of response that was being investigated.
(b) If the Klinostat was not rotating: (i) state the observations that would be made on the seedlings after three days; (ii) explain the observations in (b) (i) above. (c) If the experiment was repeated with the Klinostat rotating: (i) state the observation that was made on the seedlings after three days; (ii) give a reason for the observation made on the seedlings.
ANSWERS
​(a) Geotropism/Gravitropism;
(b) (i) The shoot tip/plumule curved upwards; root tip/radicle curved downwards; (ii) Auxins migrated downwards to lower side; Higher concentration on the lower side; caused more growth on the lower side than on the upper side in shoots inhibited growth on the lower side than on the upper side in the roots; (c) (i) The seedling will continue growing horizontally; (ii) There was even distribution of auxins (on the tips); K.C.S.E Biology Q & A - MODEL 2015PP2QN04
In an experiment to investigate a factor affecting photosynthesis, a potted plant which had been kept in the dark overnight was treated as shown in the diagram below and exposed to light.
​(a) Why was the potted plant kept in the dark overnight’?
(b) Which factor was being investigated in the experiment? (c) (i) Which test did the students perform to confirm photosynthesis in the leaves labelled P and Q? (ii) State the results obtained in the leaves labelled P and Q. P Q (iii) Explain the results obtained in the leaves labelled P and Q. P Q (d) What was the purpose of leaf Q in the experiment?
ANSWERS
(a) To destarch/remove starch from the leaves;
(b) Carbon (IV) Oxide/CO2; (c) (i) Test for starch; (ii) p - Retained the colour of iodine solution/brown/yellow; Q - Turned blue-black/black/dark-blue; (iii) P - Did not photosynthesize /no starch is formed because Sodium Hydroxide pellets absorbed Carbon (IV) Oxide; Q - Photosynthesized /starch was formed because Carbon (IV) Oxide was in the flask; (d) Control (experiment);
K.C.S.E Biology Q & A - MODEL 2015PP2QN03
A female with sickle cell trait marries a normal man. The allele for sickle cell is HbS and the normal allele is HbA. Determine the probability that their first born will have the sickle cell trait. Show your working..
K.C.S.E Biology Q & A - MODEL 2015PP2QN03
State two examples of discontinuous variation.
ANSWERS
​ (i) Sex;
(ii) ABO blood group system/Rhesus factor; (iii) Ability to roll tongue; (iv) Free or attached earlobe; (v) Presence/ absence of hair in the nose! on the ear pinna; (vi) Finger prints; ability to taste PTC (phenythiocarbamide) PTV (phenylthio urea) (vii) Winglength in prosophila; (viii) Size of abdomen in drosophila; (ix) Eye colour in prosophila; (x) Smooth/wrinkled seed coats in pea plants; (xi) Green/yellow seed coats/seed coat colour in pea plants; (xii) Polymorphism/melanic and non melanic forms in moths.
K.C.S.E Biology Q & A - MODEL 2015PP2QN03
What is meant by the term genetics?
ANSWER
K.C.S.E Biology Q & A - MODEL 2015PP2QN02
The diagram below illustrates the structure of the female part of a flower.
(a) Name the part labelled W.
(b) Describe what happens when the pollen tube enters the structure labelled V. (c) What do the structures labelled R and T develop into after fertilization? R T
ANSWERS
​ (a) W - ovary wall/ovary;
(b) Tip of pollen tube bursts open; one of the nuclei fuses with the egg cell nucleus; to form a diploid zygote; while the remaining male nucleus fuses with the polar nuclei; to form a triploid endosperm nucleus; (c) R - Endosperm/primary endosperm; T - testa/seed coat; K.C.S.E Biology Q & A - MODEL 2015PP2QN01
The diagram below illustrates a blood capillary surrounding a structure for gaseous exchange in human beings.
​(a) Name the gaseous exchange structure.
(b) Identify the gases labelled Y and Z. Y Z (c) How does the gas labelled Y reach the inside of the blood capillary? (d) How does cigarette smoking lead to lung cancer?
ANSWERS
​.(a) Alveolus;
(b) Y - oxygen/O2; Z - Carbon (IV) Oxide/CO2; (c) Oxygen concentration is lower in the blood capillary than in the alveolus; oxygen diffuses; through the epithelium and endothelium of capillary wall, plasma into the red blood cells where it combines with haemoglobin. (d) Cigarettes/tobacco contains tar; tar contains carcinogenic substances; which trigger cancer
K.C.S.E Biology Q & A - MODEL 2014PP2QN08
Describe the role of the human skin in homeostasis.
answers
When body temperature is lowered below normal; arterioles in the skin constrict; blood is diverted to a shunt system; less blood flows to the skin/less heat is lost; when body temperature is raised above normal;arterioles in the skin dilate;more blood flows to the skin; more heat is lost by convection and radiation;when body temperature is lowered below normal:erector-pilli muscle s contract, hair stands erect; more air is trapped, air is a bad conductor;and insulates the body against heat loss; when body temperature is raised above normal: erectorpi11i muscles relax, hair lies on skin;less air is trapped, more heat is lost; when body temperature is lowered below normal: less fluids are absorbed by sweat glands;less sweating, less vaporisation of water;
when body temperature is raised above normal:sweat glands are more stimulated and more sweat is produced; water in sweat evaporates and takes up heat from the body;body is cooled/body temperature is lowered;
K.C.S.E Biology Q & A - MODEL 2014PP2QN08
How does excretion take place in plants?
answers
K.C.S.E Biology Q & A - MODEL 2014PP2QN07
Describe the process of carbohydrate digestion in human beings.
answers
​In the mouth;
K.C.S.E Biology Q & A - MODEL 2014PP2QN07
Explain how each of the following factors affects the rate of photosynthesis:
(i) temperature; (ii) chlorophyll concentration.
answers
(i) Reactions in photosynthesis are catalysed by enzymes; at optimum temperature photosynthesis proceeds faster;
Below optimum temperature the rate of photosynthesis decreases because enzymes are inactivated by the low temperatures / above optimum the rate of photosynthesis decreases because enzymes are denatured; (ii) Chlorophyll traps energy from sunlight for photosynthesis; The higher the chlorophyll concentration the higher the rate of photosynthesis and vice versa; K.C.S.E Biology Q & A - MODEL 2014PP2QN06
An experiment was done to determine the uptake of nitrogen from the soil by broad bean seedlings. The experiment was done with one set of seedlings M grown in the atmosphere enriched with carbon (IV) oxide and another set up of seedlings N grown in the normal atmosphere.
The amount of nitrogen in each seedling was measured in milligrams at intervals often days. The table below shows the results obtained.
​(a) Using the same axis draw line graphs of nitrogen uptake by the two (M and N) sets of broad bean seedlings against time.
(b) Determine the rate of uptake of nitrogen in Set M between 65 and 85 days. (c) (i) What is the relationship between carbon (IV) oxide concentration in the air and nitrogen uptake? (ii) Account for the relationship in (c)(i) above. (d) (i) What would happen to the concentration of nitrogen in the seedlings in set M, if after 75 days the seedlings are transferred to a normal atmosphere. (ii) Explain your answer in (d)(i) above. (e) State three ways in which nitrogen fixation occurs.
answers
(c) (i) The higher the carbon UV) oxide content in air, the higher the nitrogen uptake and vice versa;
(ii) More Carbon (IV) oxide in the air makes the seedlings to photosynthesize more; hence more amino acids/protein; are formed in the dark stage; formation of amino acids/protein requires nitrogen; (d) (i) The concentration of nitrogen would remain constant; (ii) Despite decline in CO,; the nitrogen already absorbed/taken up by the plant will still remain: (iii) Lightning; By free-living bacteria/micro organisms; By Rhizobium (in root nodules of legumes); K.C.S.E Biology Q & A - MODEL 2014PP2QN05
The diagram below represents the transverse section of the spinal cord.
​(a) Name the part labelled H.
(b) State two functions of the fluid found in the part labelled J. (c) Give a reason for the colour of white matter. (d) Name and give the function of the enzyme found at the part labelled K. Name Function (e) On the diagram, use an arrow to show the direction of impulse transmission along the neurone labelled 1.
answers
(a) H - cell body;
(b) Has nutrients for nourishment of neurons, brain, spinal cord; ​Acts as a shock absorber for protection of spinal cord from mechanical damage; (c) Contains myelin sheaths (of neurons which are made up of fats that make it have a shiny white appearance); (d) Cholinesterase: Breaks down Acetyicholine; to acetic acid and choline; (e) Correct arrow on neurone 1 points towards the grey matter;
K.C.S.E Biology Q & A - MODEL 2014PP2QN04
Explain why people with sickle cell trait have an adaptive survival advantage over normal individuals in malaria endemic regions.
answers
K.C.S.E Biology Q & A - MODEL 2014PP2QN04
Differentiate between sickle cell anaemia and sickle cell trait.
answers
K.C.S.E Biology Q & A - MODEL 2014PP2QN04
How is sex determined in man?
answers
K.C.S.E Biology Q & A - MODEL 2014PP2QN03
​(a) Describe the mechanism of gaseous exchange in plants through the lenticels.
(b) Explain each of the following: (i) the tracheoles lack spiral bands of chitin; (ii) the floor of the mouth is lowered during inhalation in a bony fish.
answers
​(a) O2, concentration is higher outside than inside the lenticels; O2, diffuses into lenticels; then into the cells; CO2 concentration is higher inside the lenticels than on the outside CO2 diffuses out of the lenticels into the atmosphere;
(b) (i) To provide a large surface area! make them thin; for gaseous exchange to reduce diffussion distance for respiratory gases; (ii) This increases the volume of the buccal cavity while decreasing the pressure; which forces water to rush into the mouth; K.C.S.E Biology Q & A - MODEL 2014PP2QN02
The diagram below illustrates the role played by red blood cells in the transportation of carbon (1V) oxide.
​(a) Other than the carbon (IV) oxide transportation in the red blood cells, name the other form of carbon (1V) oxide transportation in humans.
(b) (i) Name substance F (ii) Name the enzyme marked C and state its role in the reaction. Enzyme Role (c) Explain why transportation of carbon (1V) oxide in red blood cells is advantageous. (d) Explain the role of calcium ions in blood clotting.
ANSWERS
​(a) Carbonic acid/carbaminohaemoglobin/hydrogen carbonate;
(b) (i) Water; (ii) Carbonic acid; Role: catalyses reaction between carbon IV oxide and water to form (weak) carbonic acid; (c) Prevents accumulation of acidity/maintains pH of blood since hydrogen ions combine with haemoglobin to form Haemoglobin acids; Faster; due to the catalytic effect of carbonic anhydrase; (d) Activates thromboplastin; thrombokinase to neutralize heparin/convert prothrombin to thrombin; |
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