K.C.S.E Biology Q & A - MODEL 2019PP2QN02

K.C.S.E Biology Q & A - MODEL 2019PP2QN02

The table below shows results of blood cell counts per mm3 of blood from a sample of people living at different altitudes.

​(a) Explain the relationship between:
(i) red blood cells count and the altitude; 
(ii) white blood cells count and the altitude. 
(b) Explain why chances of nose-bleeding increase with altitude in humans.

answers

(a) i) Number of red blood cells increase with altitude; to increase oxygen carrying capacity (by haemoglobin molecules in blood); since oxygen concentration is lower at higher altitude;
ii) white blood cells serve to protect the body against harmful microorganisms/pathogens; thernadites of pathogen of the body to microbial attack is not dependent on the altitude (to be countered by the white blood cell); hence 6 the number of white blood cell count is constant at whatever altitude;
 (b) Atmospheric Pressure decreases with the increase in altitude; the imbalance between the (outer)      atmospheric pressure at high altitude and the internal blood pressure (generated by the heart) results in (one) nose bleeding at high altitudes/ internal blood pressure is higher than the (outer) atmospheric pressure.