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K.C.S.E Biology Q & A - MODEL 2000PP1QN19
How are leaves of mesophytes suited to their functions
answers
​Broad/ wide/ flat lamina provides large surface area for absorption of (O) and sunlight, thin to ensure short distance of CO2 reach photosynthesis/ palisade cells; presence of stomata guard cells for efficient diffusion of O2 gaseous exchange / H2O vapour transpiration/ CO2 into the leaf transparent cuticle epidermal cells; for light penetration into palisade cell which contains chloroplast next to upper epidermis; these receives maximum light for photosynthesis. Chloroplasts have chlorophyll, which traps light energy.
Leaves have vein, xylem and phloem to transport products of photosynthesis to other part of the plant. Air spaces on spongy mesopyll, easily circulates gases/ CO2 diffuse into palisade cells. Mosaic arrangements of leaves; enable leaves to trap sunlight.
K.C.S.E Biology Q & A - MODEL 2000PP1QN18
Describe the role of hormones in the human menstrual cycle
answers
​Inferior lobe of pituitary gland secretes F.S.H which causes grafian follicle develops in the ovary. It also stimulates ovary tissue/ ovary/ follicle walls secret estrogen which repairs, heals uterine wall, oestrogen stimulates inferior lobe of pituitary gland produce L.H. for ovulation. It also causes grafian follicle change into corpus interim L.H stimulates corpus luteum secret progesterone which causes proliferation of the uterine walls; in preparation of implantation; oestrogen/ progesterone inhibits the production of F.S.H ( by anterior lobe of pituitary) thus no more follicle develop; and oestrogen production reduces; 14 days later progesterone level rises inhibits production of L.H from anterior lobe of pituitary gland produce L.H for ovulation. It also causes grafian follicle change into corpus interim L.M stimulates corpus luteum secret progesterone which causes proliferation of the uterine walls in preparation of implantation; oestrogen/ progesterone inhibits the production of F.S.H ( by anterior lobe of pituitary) thus no more follicle develop; and oestrogen production reduces; 14 days later progesterone level rises inhibits production of L.H from anterior lobe of pituitary gland/ The corpus luteum stops secreting progesterone, and menstruation occur when the level of progesterone drops; ( anterior lobe of pituitary starts secreting F.S.H again.
K.C.S.E Biology Q & A - MODEL 2000PP1QN17
The numbers of different types of animals supported by a square kilometer in two terrestrial ecosystems are shown in the table below
(a) (i) Which domestic animal is better adapted to both ecosystems?
(ii) Give a reason why the animal named in (a) (i) above is better adapted to the two ecosystems. (b) Why are cattle and sheep fewer in the bush land than in the savannah? (c) (i) Name suitable methods that were used to estimate the population of: Domestic animals Wild animals (ii) Give a reason why the method named for wild animals in (c) (i) above is suitable (d) state three methods which could be used to determine the diet of wild animals in an ecosystem (e) Name four biotic factors that could have regulated the animal population in both ecosystems (f) State four human activities that affect population of animals in game parks (g) What is the importance of national park to a nation?
answers
​(a) (i) Goat
(ii) It is a grazer and a browser (b) Insufficient grass in bush/ aren’t adapted to eating twigs/ not browsers/ are grazers (c) (i) Domestic animals - total counts Wild animals – total counts; aerial counts/ quadrat/ Belt transect/ capture/ recapture (ii) Analyzing gut counts, studying dentition/ breaks/ claws/ parts (d) Observation Examine droppings Dissecting a sample of animals/ study structure/ nature of digestive System/ size of caecum/ length of intestine/ chamber (e) Irrigation Competition; diseases Predation; human activity/ man accept any correct Parasitism (f) Poaching, cropping/ culling/ licensed spot hunting (g) Pollution; translocation Burning trees, charcoal- deforestation
K.C.S.E Biology Q & A - MODEL 2000PP1QN16b
State three advantages of asexual reproduction
answers
K.C.S.E Biology Q & A - MODEL 2000PP1QN16a
What is the significance of sexual reproduction?
answers
K.C.S.E Biology Q & A - MODEL 2000PP1QN15
The concentration of the lactic acid in blood during and after an exercise was determined. The results are shown in the graph below
(a) (i) By how much did the lactic acid increase at the end of 13 minutes?
(ii) After how many minutes was the lactic acid concentration 71mg/100cm3? (iii) What would be the concentration of lactic acid at the 60th minute? (b) Give a reason for the high rate of production of lactic acid during the Exercise (c) Give a reason for the decrease in the concentration of lactic acid after the exercise
answers
​(a) (i) 78/78 mg/ 100cm3
(ii) 8.5th and 29.5th / 8min 30 sec and 29 min 30 sec (iii) 47 mg/100cc; Acc. 47 (b) The demand for oxygen is more than the supply leading to anaerobic respiration. Acc. Lactic acid converted to glucose/Glycogen (c) Lactic acid is oxidized ( to form CO2 and H2O) Acc. Lactic acid is converted to glucose/ glycogen K.C.S.E Biology Q & A - MODEL 2000PP1QN14
(a) Name the crop infested by phytophthora infestant and the disease it causes Crop / Disease
(b) State four control measures against the disease
answers
​(a) Crop
Potatoes / tomato Disease Tomato/potato bright/ Acc. Tomato rot (b) Use of fungicides Eradication of infected crop/ uprooting/ burning of infected plants Use biological control Use of disease resistant varieties Crop rotating K.C.S.E Biology Q & A - MODEL 2000PP1QN13
The temperature of a person was taken before, during and after taking a cold bath. The results are shown in the graph below
(a) Explain why the temperature fell during bath
(b) What changes occurred in the skin that enabled the body temperature to return to normal?
answers
​(a) Heat loss by conduction/ convection from the blood vessels
The body skin to the cold water, the cooler blood leaving skin enters general circulation cooling the whole body. (b) Vasoconstriction; thus less blood flowing to the skin reducing heat loss. Sweating eases heat produced through metabolism Accept shivering producing heat K.C.S.E Biology Q & A - MODEL 2000PP1QN12
The chart below represents the result of successive crosses, staring with redflowered plants and white flowed plants and in which both plants are pure breeding.
(a) What were parental genotype? Use letter R to represent the gene for red colour and r for white colour
(b) (i) What was the colour of the flowers in the first filial generation? (ii) Give a reason for your answer in b (i) above (c) If 480 red flowered plants were obtained in the second filial generation, how many F2 plants and white flowers? Show your working.
answers
(a) RR and rr
(b) (i) red (ii) complete dominant; i.e Rd dominant/ white recessive (c) Ratio of filial generation: 3: 1 (I.e. in every 4 flowers 3 are red 1 is white Therefore 480 red flowers means ¾ of the total number Total number of flowers (480 x 4)/3 = 640 So ¼ of 640 flowers are white in F2 plants ¼ x 640 = 160 flowers K.C.S.E Biology Q & A - MODEL 2000PP1QN11
The diagram below represents a section of a leaf.
(a) Name the parts labeled X, and Y
(b) Using arrows indicate on the diagram the direction of flow of water during the transpiration stream (c) State two ways in which the leaf is suited to gaseous exchange
answers
​(a) X– Spongy mesopyll ( cell) layer
(b) Y – Cuticle (c) Broad/ flat leaf ( lamina) to provide large surface area or absorption of gases Thickness: allow gases to pass though fast Presence of stomata for efficient diffusion of gases Presence of air spaces for easy defuses
K.C.S.E Biology Q & A - MODEL 2000PP1QN10
Explain how birds of prey are adapted to obtaining their food.
answers
K.C.S.E Biology Q & A - MODEL 2000PP1QN09
State two advantages of metamorphosis to the life of insects.
answers
K.C.S.E Biology Q & A - MODEL 2000PP1QN07
Why is oxygen important in the process of active transport in cells?
answers
K.C.S.E Biology Q & A - MODEL 2000PP1QN07
Give reason why each of the following is important in the study of evolution:
a) Fossils records b) Comparative anatomy.
answers
(a) Fossils records
Gives evidence of types of plants/ animals/ organism that exist at a certain geological age. Long ago Gives evidence of morphological/ anatomical. Structure/ changes that have occurred over a long period of time. (b) Comparative anatomy. Gives evidence of relationship among organisms Gives evidence of common ancestry of a group of organisms; e.g. structural/ functional relationship among organization
​K.C.S.E Biology Q & A - MODEL 2000PP1QN06
Give a reason why lumbar vertebrae have long and broad transverse process
answers
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