(a) Why do people living in high altitude have more haemoglobin and high RBC count?
(b) State Allen's rule and function of blubber.

OR

(a) Draw labelled diagrams of stable and declining age pyramids of human population.
(b) Define ‘zero population growth rate’. Draw an age pyramid for the same.

(a) People living on higher altitudes have to compensate the low oxygen availability as height increases, atmospheric pressure tends to decrease. More numbers of haemoglobin and RBCs count helps in transporting more oxygen.

(b) According to Allen’s rule, mammals living in colder climates generally have shorter ears and limbs to minimise heat loss. Thick layer of fat (blubber) reduces loss of body heat. Blubber acts as an insulator occur below the skin.

OR

(a)

(b) When natality equals mortality the growth rate reaches zero. This is called as zero population growth rate.

No. of birth + Migrants = No. of deaths + Emigrants