Mastering KCSE Biology with Comprehensive Topical Questions and Answers
K.C.S.E Biology Q & A - MODEL 2006PP2QN07
Describe how human kidney functions
answers
The afferent arteriole which is the branch of renal artery supplies blood to glomerulus; The afferent arteriole has a wider diameter than the afferent arteriole; this causes high pressure; leading to ultra filtration. The walls of the blood capillaries are one cell thick hence glucose, amino acids, (vitamins, hormones) salts, (creatinine) urea and water filter into Bowman’s Capsule to form glomerular filtrate; White blood cells/ red blood cells and plasma proteins such as (Globulin, fibrinogen, platelets) are too large to pass through the capillaries: the filtrate flow into the proximal convoluted tubule; where amino acids (vitamin) and all glucose are selectively reabsorbs back into the blood stream. Many mitochondria provides energy for re- absorption of these substances against concentration gradient/ by active transport. The Glomerular filtrate flow into loop of henle. Water in descending loop moves by osmosis into the blood capillaries; sodium chloride is actively pumped from the ascending arm of loop henle into the blood capillaries. The glomerular filtrate flow into the distal convoluted tubule, water is absorbed from distal convoluted tubule into blood capillaries; the glomerular filtrate flows into collection tube/ duct from where more water is reabsorbed into the blood stream.
Antidiuretic hormone influences the amount of water reabsorbed ( depending on osmotic pressure of blood); The glomerular filtrate from collecting duct now referred to as urine; is emptied into pelvis. The urine passes though pelvis and ureter into bladder out of the body through urethra.
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K.C.S.E Biology Q & A - MODEL 2006PP2QN04
The diagram below represents a traverse section through a plant organ
​A. From which plant organ was the section obtained?
B. Give two reasons for your answer in (a) above. C. Name the parts labeled J,K and L. D. State two functions of the part labeled M.
answers
(a) Root
(b) Presence of root hairs Presence of endodermis Xylem star shaped at centre Phloem at arms of the xylem (c) J- Epidermis K- Phloem L – Xylem (d) - Absorption of water Absorption of minerals salts
K.C.S.E Biology Q & A - MODEL 2006PP1QN24
State four ways in which respiratory surfaces are suited to their function.
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K.C.S.E Biology Q & A - MODEL 2006PP1QN13
State the economic important of anaerobic respiration in plants.
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K.C.S.E Biology Q & A - MODEL 2006PP1QN13
In what form is energy stored in muscles
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K.C.S.E Biology Q & A - MODEL 2006PP1QN07
state three functions of blood other than transport.
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K.C.S.E Biology Q & A - MODEL 2006PP1QN07
Name one defect of circulatory system in humans.
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State two ways in which floating leaves of aquatic plants are adapted to gaseous exchange.19/6/2020
K.C.S.E Biology Q & A - MODEL 2006PP1QN05
State two ways in which floating leaves of aquatic plants are adapted to gaseous exchange.
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K.C.S.E Biology Q & A - MODEL 2006PP1QN04
What is the role of sweat in human skin?
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K.C.S.E Biology Q & A - MODEL 2006PP1QN04
Name the fluid that is produced by sebaceous glands.
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K.C.S.E Biology Q & A - MODEL 2006PP1QN03
How is support attained herbaceous plants?
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K.C.S.E Biology Q & A - MODEL 2006PP1QN03
Name two tissues in plants which are thickened with lignin.
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​K.C.S.E Biology Q & A - MODEL 2005PP1QN18
Describe how gaseous exchange takes place in terrestrial Plants.
answers
Gaseous exchange in terrestrial plants.
Gaseous exchange in plants involves two main respiratory gases: carbon IV oxide and oxygen. During daytime green plants take in carbon IV oxide for photosynthesis and oxygen for respiration. During photosynthesis oxygen is given out as a by product and released to the atmosphere. In plants such as the flowering plants stomata in the leaves and lenticels in the woody stems and pneumatophores/breathing roots in aquatic woody plants provide the surface for gaseous exchange. Gaseous exchange taken place by diffusion across the respiratory surface. Stomata These are located mainly in the leaves and in younger parts of the stem. The opening and closing of stomata is controlled. Mainly by the intensity of light. They are normally open during the day and closed during the night. Several theories explaining the mechanism of stomata opening and closing have been put forward. 1. Photosynthetic theory Guard cells have chloroplasts. During daylight, they carry out photosynthesis producing surges. The surges increase the osmotic pressure of the cell sap. This causes water to more into guard cells from the neighboring epidermal cells by osmosis. The results is an expansion and increase in turgidity of the guard cells causing the stomata to open. In darkness photosynthesis stops. The sugar in the guard cells is converted to starch. This lowers the osmotic pressure of guard cells causing the to lose water to neighboring cells by osmosis. The guard cells become flaccid and the stomata close. The guard cells become flaccid and the stomata close. 2. Starch – sugar interconversion: The enzymatic conversion of starch to sugar proceeds more readily in an alkaline environment(high PH).The conversion of sugar to starch occurs more readily in an acidic environment (low Ph).During the night, when photosynthesis is not taking place, carbon dioxide accumulates in leaf cells it combines with water to form carbonic acid. This lower the PH in the guard cells leading to conversion of sugar to starch this decreases the osmotic pressure in the guard cells causing them to lose water to the neighboring epidermal cells. The guard cells become flaccid and the stomata close. During daylight, when photosynthesis is taking places, the concentration of carbon dioxide in the leaf cells, raising their PH, and favouring the conversion of starch to sugar. This increases the osmotic pressure in the guard cells causing them to take in is an expansion and increase in turgidity of the guard cells causing the stomata to open. 3. Potassium Ion (K+) mechanism When guard cells are exposed to light, their chloroplasts manufacture ATP. The ATP drives at K+ pump in the cell membrane of the guard cells. This causes an active uptake of K+ into the guard cells from surrounding epidermal cells. Accumulation of K+ in guard cells increases the osmotic pressure of their cell sap. This causes water to move into the guard cells from neighbouring epidermal cells by osmosis. The result is an expansion and increase in turgidity of the guard cells causing the stomata to open. -At the onset of darkness, chloroplast stop making ATP and its concentration in guard cells falls rapidly stopping K+ pump, K+ migrate from the guard cells Causing them to lose water to the neighbouring cells by osmosis. The guard cells become flaccid and the stomata close. -Water molecules are pumped into the guard cells from adjacent epidermis cells. -A small extent of gaseous exchange takes place in the stem through structures called lenticels. These are small gaps in the bark usually circular or oval & slightly raked on the bark surface. The cells in these area are thin walled and loosely packed leaving air space which communicates with air spaces in the cortex. Hence 02 for respiration is taken up & C02 is given out. K.C.S.E Biology Q & A - MODEL 2005PP1QN14
A set up that was used to investigate certain process in plants is shown in the diagram below.
​a) What process was being investigated?
b) (i) State two precautions that should be taken when setting up the experiment. (ii) Give a reason for each precaution stated in b(i) above. c) State three environmental factors that influence the process Under investigation.
answers
a) Transpiration
b)i) The leafy shoot should be from herbaceous plant Cut off the last few centimeters of the stalk under water All the air in the capillary tubule should be expelled Jelly should be applied around the stem around the rubber bung. The end of the capillary fusing should rest in beaker of water. ii) Avoid air bubbles. For continuity of the flow of water Jelly should not touch the xylem vessels because it might block they xylem. To avoid introduction of air bubbles in the xylem. For continuity of water uptake. c) Temperature Humidity Wind Atmospheric pressure Light intensity Availability of water K.C.S.E Biology Q & A - MODEL 2005PP1QN13
The diagram below shows a section through the mammalian skin.
a) Name the parts labeled E, F and G.
E ………………………………………… F ………………………………………… G ………………………………………… b) State two functions in each case of substance secreted by the structures labeled. (i) H ………………………………… (ii) I ………………………………….
answers
​a) E – Malpighian layer
F – Nerve cell G – Erector pili muscle b)i) H – Excretion of waste products of metabolism from the body e.g. excess. Water, mineral salts traces of urea, lactic acid etc. Temperature regulation in the body brings a cooling effect through Loss of excess heat by evaporation of water. Keeps the hair and epidermis flexible and water proof Contains antiseptic substances for protection against bacteria. K.C.S.E Biology Q & A - MODEL 2005PP1QN11
The diagram below represents a part of the rib cage.
​a) Name the parts labeled W, Y and Z.
W …………………………………………………… Y ……………………………………………………. Z …………………………………………………….. b) How does the part labeled Z facilitates breathing in?
answers
​a) W – Spinal column / reutebral column
Y – Sternum Z – Intercostal muscles. b) The external intercostals muscles contract while the internal intercostals. Muscles relax. This movement pulls the ribs upwards and outwards. The diaghragm muscles contracts (flattens).The thoracic volume increase while the pressure reduces, leading to atmospheric air rushing into the lungs through the nose and trachea hence inflating the lungs.
K.C.S.E Biology Q & A - MODEL 2005PP1QN09
Why would carboxyhaemoglobin lead to death?
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Name the substance which accumulates in muscles when respiration occurs with insufficient oxygen.18/6/2020
K.C.S.E Biology Q & A - MODEL 2005PP1QN06
Name the substance which accumulates in muscles when respiration occurs with insufficient oxygen.
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K.C.S.E Biology Q & A - MODEL 2004PP1QN18
How is the mammalian skin adapted to its functions?
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K.C.S.E Biology Q & A - MODEL 2004PP1QN15
a) Give the differences between the following structures in wind and insect pollinated flowers.
i) Anther ii) Pollen grains iii) Stigma b) What is the importance of cross pollination? c) Explain how a seed is formed after an ovule is fertilized
answers
​(i) anther Insect Wind
Small short anther firmly Large/ long anthers/ loosely attached to Attached to elements filaments (ii) Large heavy/ spiky small/ light/ smooth (iii) Small/ sticky Long feathery (b) Source of variation/ hybrid acc. Production of hybrid K.C.S.E Biology Q & A - MODEL 2004PP1QN13
The diagram below shows a vertical section through a mammalian heart.
​a) Name the parts labeled A,B,E and F
b) Use arrows to show the direction in which blood flows in the heart. c) Give a reason why the wall of chamber C is thicker than chamber D
answers
(a) A Pulmonary vein
B Left atrium I auricle E Tricuspid valve F Pulmonary artery
​(b) The left ventricle ‘C’ pumps blood a longer distance to all parts of the body; while the right ventricle ‘D’ pumps blood to a shorter distance/ to the lungs; therefore the left ventricle has thicker walls to generate exert more pressure.
K.C.S.E Biology Q & A - MODEL 2004PP1QN10
How are the xylem vessels adapted for support?
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K.C.S.E Biology Q & A - MODEL 2004PP1QN09
Name two mineral elements that are necessary in the synthesis of chlorophyll.
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K.C.S.E Biology Q & A - MODEL 2004PP1QN04
Other than carbon dioxide, name other products of anaerobic respiration
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K.C.S.E Biology Q & A - MODEL 2004PP1QN03
How is aerechyma tissue adapted to its function
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