K.C.S.E Biology Q & A - MODEL 2014PP2QN01
​(a) State four characteristics of fruits dispersed by animals.
(b) State two roles of each of the following hormones in menstruation: (i) luteinising hormone; (ii) oestrogen.
ANSWERS
​(a)
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K.C.S.E Biology Q & A - MODEL 2013PP2QN08
Describe the role of the following organs in excretion and homeostasis.
(a) the liver (b) the skin during hot environmental conditions.
ANSWERS
​(a) Regulation of blood sugar ; when blood sugar is below normal/90 mg/100 cm3 glucagon ; triggers the conversion of glycogen to glucose in the liver ; the glucose is released into the blood stream. When blood sugar is in excess above normal/10 mg/100cm3, insulin; causes the liver to convert glucose excess to glycogen ; which is stored.
Production of heat energy ; by increasing the rate of metabolic activities: Excretion of bile pigments ; produced due to breakdown of worn out red blood cells: Deamination/removal of amino group of excess amino acids to form urea: and detoxication/poisonous/toxic substances: (b) Sweat glands excrete urea; excess water; and salts: hence maintaining salt & water balance in the blood. Evaporation of sweat; cools the body due to loss of latent heat of vaporization; when the body temperature rises : blood vessels in the skin vasolidate: allowing more blood to flow near the skin surface: thus heat is lost to the environment radiation/convection. The eretor pili mucle relaxes hair flattens ; in a hot environment reducing insulation: hence heat is lost from the body by radiation! convection; to the environment.
K.C.S.E Biology Q & A - MODEL 2013PP2QN07
How are respiratory surfaces in mammals adapted to their functions?
ANSWERS
Many to provide a large surface area: across which large amounts of gases diffuse: moist surfaces: to dissolve respiratory gases: so as to diffuse. Made of a thin membrane/epithelium/one cell thick wall ; to reduce diffusion distance;
Highly vascularized: to carry away oxygen; and bring in carbon (IV) oxide: creating a steep diffusion gradients.
K.C.S.E Biology Q & A - MODEL 2013PP2QN07
Describe the process of blood clotting in human beings.
ANSWERS
When a blood vessel is cut/injured platelets/thrombocytes/damaged tissue/wound is exposed to the air: they release thrombokinase/thromboplastin ; an enzyme that activates the conversion of prothrombin: to thrombin: in the presence of calcium ions: vitamin K/ phylloquinone ; is needed for the formation of prothrombin; Thrombin converts (soluble blood protein) fibrinogen ; into (the fibrous form) fibrin; which forms a mesh / network across the wound: The clot so formed prevents excessive bleeding: and entry of disease agents/pathogens/micro-organisms/microbes;
K.C.S.E Biology Q & A - MODEL 2013PP2QN06
A scientist carried out an investigation to find out the population growth of mice under laboratory conditions. Twenty young mice were placed in a cage. The results obtained from the investigation were as shown in the table below.
​(a) On the grid provided, draw a graph of the number of mice against time.
GRAPH PAPER (b) Account for the changes in mice population between (i) O to 2 months (ii) 2 to 6 months (iii) 6 to 10 months (iv) 10 to 12 months. (c) (i) Between which two months was the population change greatest? (ii) Calculate the rate of population change over the period in (c)(i) above. (d) What change in population would be expected if the investigation was continued to the 19th month? (e) To obtain the observed results state two variables that were kept constant during the investigation.
answers
(b) (i) No change in population/population is constant: mice still maturing/have not given birth:
(ii) Slow/gradual population growth; few mice have reached sexual maturity; (iii) Faster/rapid rate of population growth/exponential; Many mice sexually matured/reproducing/enough food/space/no competition birth rate higher than death/no diseases: (iv) Population decline; Competition is high / food is limiting / space is limiting/accumulation of toxic waste/disease (outbreak) deathrate higher than birth rate. (c) (i) 6 and 8; (ii) 310-115 = 195 mice per month; (d) Population would increase; (e) Food; space ; cage size; water; K.C.S.E Biology Q & A - MODEL 2013PP2QN05
The diagram below represents a mammalian pelvic girdle.
​(a) How are the structures labelled H and J adapted to their function?
(i) H (ii) J (b) State the function of obturator foramen. (c) (i) Name the bone that articulates with the pelvic girdle at acetabulum. (ii) Name the type of joint formed by the acetabulum and the bone named in (c)(i) above. (d) Name the bone formed by the fusion of caudal vertebrae inhuman beings.
answers
K.C.S.E Biology Q & A - MODEL 2013PP2QN04
In an investigation, a variety of pea plants grown from seeds with smooth coats were crossed with plants grown from seeds with wrinkled coats. All the seeds obtained in the first filial (F1) generation had smooth seed coats.
​(a) Using the letter R to represent the gene for smooth seed coat, work out the genotype of the F1 generation. Show your working.
(b) If the F1 generation was sel fed, determine the phenotypic ratio of the second filial (F,) generation. Show your working. (c) If the total number of seeds in the F, generation was 14 640, calculate the number of seeds with wrinkled coats. Show your working. K.C.S.E Biology Q & A - MODEL 2013PP2QN03
(a) Explain the importance of the following in photosynthesis:
(i) light; (ii) carbon(IV) oxide; (iii) chlorophyll.
(b) Name one appropriate food substance for each of the following enzymes:
(i) ptyalin (ii) pepsin (c) State the cause and two symptoms of Ben-ben. Cause Symptoms ​
answers
​(a) (i) Provides energy needed to split water molecules into oxygen and hydrogen/photolysis;
Provides energy for formation of ATP molecules (which is used in dark stage) (ii) Combines with hydrogen ions to make glucose; (iii) Used to trap light energy; (b) (i) Starch; (ii) Protein; (c) (i) Lack of vitamin B1/thiamine; (ii) . Stunted growth; Paralysis of legs/arms/limbs/damage to peripheral nerves; Heart failure Swelling of feet/oedema Gastrointestinal disturbances/loss of appetite/constipation/diarrhoea/vomiting; Weight loss/muscle wasting Pale skin K.C.S.E Biology Q & A - MODEL 2013PP2QN02
The diagram below represents the human ear.
​(a) Name the parts labelled E, F and G.
E F. (b) How is each of the following adapted to its function? (i) External auditory meatus; (ii) Ear ossicles. (c) Name one defect of the human ear.
answers
K.C.S.E Biology Q & A - MODEL 2013PP2QN01
The diagram below represents a plant in the division Bryophyta.
​(i) Name the parts labelled B and D.
B D (ii) State one function for each of the parts labelled A and C. A C (b) The diagram below represents a member of the kingdom Animalia.
​(i) Name the phylum to which the organism belongs.
(ii) Using observable features in the diagram, give three reasons for the answer in b(i).
answers
​(a) (i) B Seta/stalk;
D Rhizoid: (ii) A Production of spores/sporulation; C Photosynthesis; (b) (i) Arthropoda; (ii) Segmented body; Jointed appendages; Presence of exoskeleton Describe how environmental factors increase the rate of transpiration in terrestrial plants.26/6/2020
K.C.S.E Biology Q & A - MODEL 2012PP2QN08
Describe how environmental factors increase the rate of transpiration in terrestrial plants.
ANSWERS
In bright light; stomata are fully/wide open; increasing contact between the atmosphere and air spaces in the leaf; This in turn increases water loss by evaporation through the
open stomata High environmental temperatures; increase the rate of evaporation from the leaf surface thus more water leaves cells due to the increased diffusion gradient; Iii a windy day; air around the leaf is carried away reducing water vapour around the leaf; more water moves into the atmosphere from the leaf air spaces; In low humidity/when the atmosphere is less saturated with water vapour; more water will move from leaf air spaces into the atmosphere; leading to increased rate of transpiration; . Low atmosphere pressure; increases diffusion gradient between atmospheric and leaf increased rate of evaporation;Availability of water; causes turgidity of guard cells hence stomata open; increasing rate of transpiration.
K.C.S.E Biology Q & A - MODEL 2012PP2QN08
Using a relevant example, describe how an allergic reaction occurs in a human being.
ANSWERS
​An allergic reaction is a hypersensitive response; to an antigen by the body immune
system; The body immune system responds by overproducing antibodies; against harmless antigens; The antigen-antibody reaction occurs on the surface of body cells; which burst open; and release histamines; Histamines cause inflammation/itching! swelling/pain, et.c; which damage the body; Allergic people are hypersensitive to materials like dust/pollen grains/some foods/some drugs/some pollutants,
K.C.S.E Biology Q & A - MODEL 2012PP2QN07
Using a relevant example in each case, describe simple and conditional reflex actions.
ANSWERS
Simple reflex action - withdrawal of finger from a sharp object.
Is an automatic response to a specific stimulus; When the finger touches a sharp object, pain receptors in the skin; are stimulated and trigger off a nerve impulse; The nerve impulse is transmitted via the sensory neuron; to the grey matter of the spinal cord; The impulse is then transmitted via a synapse; to the relay neuron; and then through another synapse; to the motor neuron; The impulse is then transmitted to the effector muscles in the hand; These effector muscles contract; and the finger is withdrawn from the hot object; Conditioned reflex action Is an automatic response evoked from an animal by unrelated stimulus; substituted for the one which normally elicits the response; It develops from past experience; and involves modification of behaviour through learning; It weakens with time; and must be reinforced by repeating the unrelated stimulus; Students salivate when the bell for lunch rings; because they have learned to associate the ringing of the bell at lunchtime with food; from experience; every time it rings, they are offered food; K.C.S.E Biology Q & A - MODEL 2012PP2QN06
The data provided below represent populations of a predator and its prey over a fifty years’period.
​(a) (i) Using the same axes, draw graphs of the relative populations of P and Q against time.
(ii) With a reason, identify the curve that represents the prey. (iii) Account for the two populations between 25 arid 32 years. (iv) Which years were the two populations equal? (v) A part from predation, state three biotic factors that may have led to the decline of the prey population. (b) Describe the hazards of air pollution by Sulphur (IV) Oxide.
answers
(a) (i) title - Graph of Prey-predator relationship; (OWTE)
Scales X axis; Graph should cover more than half of the grid provided. Y axis; Graph should cover more than half of the grid provided. correct plotting P; Q; smooth curves P; Q; labelling axes;
(ii) P represents the prey;
Prey population is initially higher prey population usually starts falling earlier; (iii) Both populations decrease; because prey is not enough to sustain predator/population environmental stress limit population of prey; (iv) at 23±0.5 years; and at 39±0.5; (v) less food for the prey/intra specific competition; emigration of the prey; diseases causing death of the prey; parasitism; human activities b)sulphur dioxide in the air - causes respiratory diseases; poisons plants; forms acid rain which increase soil pi-J; corrodes metals in buildings;
K.C.S.E Biology Q & A - MODEL 2012PP2QN05
Explain the mechanism of stomatal opening.
answers
The osmotic pressure of guard cells increase when sugar is manufactured during photosynthesis/starch is converted to sugar in low acidity/potassium moves into guard cells during the day; water enters guard cells from the surrounding cells by osmosis; because the guard cells are bean shaped with thin outer walls and thick inner walls, the thin outer walls expand faster as the cell becomes turgid; thus the thick inner wall curves; causing the stomatal aperture to open.
K.C.S.E Biology Q & A - MODEL 2012PP2QN05
Describe the process of inhalation.
answers
K.C.S.E Biology Q & A - MODEL 2012PP2QN04
The diagram below illustrates arrangement of bones and muscles of the human arm.
​(i) Name the bones labelled K and L.
K L (ii) Explain how the upward movement of the lower arm is brought about by the, bones and muscles shown in the diagram above. (b) State three ways in which support is brought about in a leaf.
answers
​(a) (i) K - ulna;
L - humerus; (ii) movement of the lower arm upwards takes place at the elbow/olecranon process which is between the ulna and the humerus; biceps/flexor muscles contract; while the triceps/extensor muscles relax; bringing about the movement of the lower arm upwards. , (b) The rigid midrib holds leaf out away from the stem; Profuse network of veins have lignified cells which support leaf to stay spread out; Turgidity in spongy mesophyll and palisade cells support the leaf to remain open; K.C.S.E Biology Q & A - MODEL 2012PP2QN03
(a) In an investigation, equal amounts of water was placed in. three test-tubes labelled G, H and J. Pondweeds of equal length were dropped in each test tube. The test-tubes were then placed in identical conditions of light and carbon (IV) oxide at different temperatures for five minutes. After the five minutes, the bubbles produced in each test-tube were counted for one minute. The results were as shown in the table below.
​(i) Name one requirement for this process that is not mentioned in the investigation.
(ii) Name the gas produced in this investigation. (iii) Account for the results in test-tubes H and J. (b) State two ways in which the human intestinal villus is adapted to its function.
answers
​(a) (i) chlorophyll;
(ii) oxygen; (1 mark) (iii) Test tube H is at optimum temperature for enzyme activity; hence high rate of photosynthesis/more bubbles. In test tube J most enzymes have been denaturedby the high temperature; hence low rate of photosynthesis/fewer bubbles. (b) — The villus epithelium is thin; for faster diffusion of dissolved food substances; — The epithelium has goblet cells; which produce mucus to lubricate food passage; — They have microvilli; which further increase their surface area for absorption; Have lacteal; for absorption of fatty acid & glycerol/transportation of lipids; Highly vascularised; for absorption of digested food. K.C.S.E Biology Q & A - MODEL 2012PP2QN02
The diagram below illustrates the structure of the kidney nephron.
(a) Name the part labelled E.
(b) How is the part labelled F adapted to its function? (c) State three physiological mechanisms of controlling the human body temperature during a cold day.
answers
K.C.S.E Biology Q & A - MODEL 2012PP2QN01
In a certain plant species which is normally green, a recessive gene for colour (n) causes the plants to be white in colour. Such plants die at an early age. In the heterozygous state, the plants are pale green in colour but grow to maturity.
(a) Give a reason for the early death of the plants with the homozygous recessive gene. (b) If a normal green plant was crossed with the pale green plant, what would be the genotype of the first filial generation (F1 generation)? Show your working. (c) If heterozygous plants were self-pollinated and the resulting seeds planted, work out the proportion of their offspring that would grow to maturity. Describe how accommodation in the human eye is brought about when focusing on a near object.25/6/2020
K.C.S.E Biology Q & A - MODEL 2011PP2QN08
Describe how accommodation in the human eye is brought about when focusing on a near object.
answers
Light rays from a near object are more diverged and need to bend more; in order to be focused properly on the retina; ciliary muscles contract; suspensory ligaments attached to the ciliary muscles relax; the lens becomes thicker; increasing its curvature/becomes more convex; light from the object is refracted more; in order to be focused/more sharply on the retina to form an image.
K.C.S.E Biology Q & A - MODEL 2011PP2QN08
Describe the exoskeleton and its functions in insects.
answers
The exoskeleton is made of chitin; chitin is not evenly distributed; hence it allows for movement; exoskeleton is secreted by the epidermal cells; when still soft it allows for growth of the insect; when in contact with the air it hardens limiting growth; It is shed regularly; thus regulating the growth of insects. It also supports the internal structures; Because it is hard; it protects; internal organs from mechanical damage. It is water proof; preventing water loss/dessication; of the insect. It also provides a surface for attachment of muscles;
K.C.S.E Biology Q & A - MODEL 2011PP2QN07
Explain how the human skin brings about cooling of the body on a hot day.
answers
Erector pilli muscle relax; and hair lie flat; trapping less air; thus reducing insulation;
Blood capillaries under the skin vasodilate; and more blood is brought under the skin; increasing heat loss; sweat glands release more sweat to the skin surface; the sweat take away heat from the body when it evaporates;
K.C.S.E Biology Q & A - MODEL 2011PP2QN07
Explain how structural features in terrestrial plants affect their rate of transpiration.
answers
Plants in arid, semi-arid and desert habitats have leaves covered with thick/waxy cuticles; that are waterproof/impermeable to water; allowing for reduced rate of transpiration; Sunken stomata; in some desert/semi arid areas plants have water vapour accumulating in the pits; reducing rate of transpiration (as the moisture in the pit is carried away by wind.) Most plants have few or no stomata on the upper surface of leaf; the fewer the stomata the less the water lost from the plant. Some plants have small stomata/stomatal size decrease when guard cells are flaccid; thus reducing transpiration rate. Plants with small/folding leaves; expose less surface area; hence reduce the rate of transpiration. Leaves with shinny surfaces; reflect light resulting
reduced leaf temperatures; thus reducing the rate of transpiration. Some plants have leaves covered with hairs/scales; which trap a layer of moisture; the leaf surface reducing rate of transpiration. Mesophyte have a thin layer of cuticle; to facilitate high transpiration rate; brad lenses exposing large area to transpiration; Many stomata on both leaf surfaces provide many apartunes to enhance transpiration.
K.C.S.E Biology Q & A - MODEL 2011PP2QN06
Explain how the osmotic pressure in the human blood is maintained at normal level.
answers
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