Question

Which two of the following changes(a-d) usually tend to occur in plain dwellers when they move to higher altitudes (3500m or more)?
a. Increase in red blood cell size
b. Increase in red blood cell production
c. Increase in breathing rate
d. Increase in thrombocyte count

A. c and d
B. a and d
C. c and b
D. b and c

Answer 1

When there is a deviation from the normal existing conditions, the body adapts to the changes and this is known as adaptation. Adaptation helps the organism to survive and the organisms which have successful against the natural selection.

Complete answer:
The organisms are well adapted to their immediate environment. These changes are physiological, and behavioral. The environmental conditions in the plain areas are very different from the high altitudes. At high altitudes, the level of oxygen is considerably low as compared to the plains. The plains have a higher oxygen level. The low level of oxygen and low atmospheric pressure at higher altitudes can cause serious consequences in the different physiological processes.
The humans are naturally adapted to conditions where oxygen is abundant. When individuals living in the plains where oxygen level is more face certain changes that occur when they move to higher altitudes. In these conditions, the people moving to higher altitudes face altitude sickness especially at an altitude of 3500m or more. The important complications are hypoxia, breathlessness, headaches, dizziness, vomiting and nausea, with dilated veins and increased heartbeat. The symptoms may be further increased to cause cerebral oedema, and pulmonary oedema.
In order to cope up with these changes, the body undergoes certain physiological changes such as increased breathing rate, increase in the production of red blood cells, and also there is decrease in the binding capacity of hemoglobin. The condition of hypoxia stimulates the kidneys to release erythropoietin which stimulates the production of RBC.
At the initial stages, there may occur an increase in the size of the RBCs but this size returns to normal when there is an increase in the numbers of RBC.
Increase in the thrombocytes occurs when there occurs blood clot in the body in certain conditions such as heart stroke, brain stroke and excessive bleeding.

Hence, the correct answer is option (D).

Note: The atmospheric conditions of a particular environment are bound to affect the development of the living organisms. The plain dwellers when move to the higher altitudes certain physiological changes occur in order to cope up with decreased oxygen levels. The important changes are increased breathing rate, increased red blood cells productions with a decreased oxygen binding capacity.