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 2015PP1QN11
Name two structures used for gaseous exchange in plants.
answers
K.C.S.E Biology Q & A - MODEL 2015PP1QN07
How is a guard cell structurally adapted for gaseous exchange?
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 2014PP1QN27
The diagram below shows the gaseous exchange system of a locust.
​(a) Name the structure labelled Q.
(b) State the function of the part labelled R. (c) How is the part labelled S structurally adapted to its function?
ANSWERS
​ (a) Spiracle;
(b) Keep the trachea open for air passage; (c) Lacks spiral bands of chitin /to make it thin; for diffusion of gases; Moist; to dissolve respiratory gases;
K.C.S.E Biology Q & A - MODEL 2014PP1QN19
Why is a burning charcoal stove in a poorly ventilated room likely to cause death of the inhabitants?
ANSWERS
K.C.S.E Biology Q & A - MODEL 2014PP1QN12
The diagram below represents a model used to demonstrate breathing in mammals.
​(a) Name the mammalian structure represented by the parts labelled D and E.
(i) D . (ii) E (b) State the observation made when the string is pulled downwards. (c) Explain the observation in (b) above.
ANSWERS
​(a) (i) Rib-cage/chest cavity;
(ii) Diaphragm; (b) The balloons are inflated; (c) Pulling down the string increases the volume of D, hence decreasing the pressure inside: The low pressure causes external atmospheric air to rush in and inflate the balloons;
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 2013PP1QN10
How are lenticels adapted for gaseous exchange?
answers
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 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 2011PP2QN03
How are the pneumatophores adapted to their function?
answers
K.C.S.E Biology Q & A - MODEL 2011PP1QN22
State the difference in content of oxygen and carbon (IV) oxide in the air that enters and leaves the human lungs.
answers
K.C.S.E Biology Q & A - MODEL 2011PP1QN20
The number of stomata on the lower and upper surfaces of two leaves from plant species X and Y were counted under the field of view of a light microscope. The results were as shown in the table below.
​(a) Which of the two leaves would be expected to have a lower rate of transpiration?
(b) Give a reason for your answer in (a) above.
answers
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