Mastering KCSE Biology with Comprehensive Topical Questions and Answers
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.
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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 2013PP1QN25
State one adaptation of xylem vessels to their function.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN24
Explain three protective functions of mammalian blood.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN15
State two reasons why accumulation of lactic acid leads to an increase in heart beat.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN14
Name the three end products of anaerobic respiration in plants.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN11
State the advantage of possessing blood group AB.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN10
How are lenticels adapted for gaseous exchange?
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN07
Explain how the following forces contribute to the movement of water up the xylem vessels:
(a) cohesion; (b) adhesion.
answers
(a) Water molecules cling to each other maintaining a continuous column of water/preventing the break of water column;
(b) Water molecules cling to the sides of the xylem vessel walls;
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 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 2012PP1QN28
State two differences between open and closed circulatory systems.
answers
Open Closed
Blood flows in haemocoel Blood confined in vessels; sinuses/body cavity directly in contact with cells Blood flows at low pressure Blood flows at high pressure; Blood lack pigments Blood has pigments for oxygen and Carbon (IV) Oxide transportation K.C.S.E Biology Q & A - MODEL 2012PP1QN23
Name the strengthening materials found in the following support tissues:
(a) collenchyrna; (b)Xylem
answers
​(a) Cellulose;
(b) Lignin;
K.C.S.E Biology Q & A - MODEL 2012PP1QN18
Why are plants able to accumulate most of their waste products for long?
answers
K.C.S.E Biology Q & A - MODEL 2012PP1QN14
Name the type of respiration that is most efficient.
b) Give a reason for your answer in (a) above
answer
a)Aerobic respiration;
b)It releases more energy per unit mass;
K.C.S.E Biology Q & A - MODEL 2012PP1QN11
State two ways in which heart muscles are special.
answers
K.C.S.E Biology Q & A - MODEL 2012PP1QN06
The diagram below represents part of the gaseous exchange system in human.
​(a) Name the parts labelled F and G.
F G (b) State one function of each of the parts labelled H and J. H J
answers
​(a) F - Bronchiole;
G - Intercostal muscles/external intercostal muscles; (b) H - (Pleural membranes) secretes encloses pleural fluid to lubricate lungs/protect lungs; J - (Diaphragm) separates chest cavity from abdominal cavity/works to effect volume and pressure changes in chest cavity necessary for inhalation and exhalation! Ventilation/breathmg;
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 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 2011PP1QN25
State one economic importance of each of the following plant excretory products.
(a) Tannin. (b) Quinine. (c) Caffeine.
ANSWERS
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