sickle cell disease
‘How could natural selection increase the number of children born with sickle-cell disease in certain regions when these individuals are unlikely to survive and produce offspring?’
Darwin’s theory proposes that 3 conditions are a requisite for natural selection to occur. They are a struggle for existence of the offspring as they are competing for limited resources, variation within species which gives some individuals advantage over others hence better chance of survival and lastly inheritance of advantageous characters to offspring which over successive generations will be common in the population helping survival of fittest over those without. This could in effect lead to change in character from one generation to the next.
In the case study the sickle cell carriers have an advantage over non carriers as in those regions a great cause of death is malaria. The sickle cell carriers seem to have some resistance to malaria and therefore survive to produce offspring, those advantageous characteristics pass on to the descendants in this case the heterozygous gene for sickle cell, the descendants will in turn be resistant to malaria and therefore have a greater probability of surviving to produce offspring as well with the advantageous sickle cell gene. The successive generations will carry on in this manner and be prevalent as the fittest depending on a higher number of successful individuals in relative to number of survivors of other individuals, the relative number of individuals that have higher fitness than others and the fact that they must reproduce.
Some regions in Africa have higher malaria risks in which selection pressure mean that number of individuals with the mutant gene for sickle cell will be higher as they will be resistant to the malaria and survive to adulthood and reproduce in comparison to the number of those individuals who although not carriers of sickle cell disease managed to survive and reproduce. Most of the non-sickle cell carriers
Darwin’s theory proposes that 3 conditions are a requisite for natural selection to occur. They are a struggle for existence of the offspring as they are competing for limited resources, variation within species which gives some individuals advantage over others hence better chance of survival and lastly inheritance of advantageous characters to offspring which over successive generations will be common in the population helping survival of fittest over those without. This could in effect lead to change in character from one generation to the next.
In the case study the sickle cell carriers have an advantage over non carriers as in those regions a great cause of death is malaria. The sickle cell carriers seem to have some resistance to malaria and therefore survive to produce offspring, those advantageous characteristics pass on to the descendants in this case the heterozygous gene for sickle cell, the descendants will in turn be resistant to malaria and therefore have a greater probability of surviving to produce offspring as well with the advantageous sickle cell gene. The successive generations will carry on in this manner and be prevalent as the fittest depending on a higher number of successful individuals in relative to number of survivors of other individuals, the relative number of individuals that have higher fitness than others and the fact that they must reproduce.
Some regions in Africa have higher malaria risks in which selection pressure mean that number of individuals with the mutant gene for sickle cell will be higher as they will be resistant to the malaria and survive to adulthood and reproduce in comparison to the number of those individuals who although not carriers of sickle cell disease managed to survive and reproduce. Most of the non-sickle cell carriers