CAPE Biology Unit 1 · 2003 · Paper 2 · Question 8(b)

Opposing environmental pressures may give rise to balanced polymorphism, in which two or more alleles are maintained in a population because each is favoured by a separate environmental force.

Suggest how environmental factors act to preserve the alleles for both normal haemoglobin and sickle cell haemoglobin in native Africans living in Africa.