Explain how malaria and sickle cell anemia are selection pressures that stabilize the sickle cell allele frequency in a population

Sickle cell anemia is a homozygous recessive disorder. This means, in order to have sickle cell anemia, you must have two copies of the recessive allele (aa). Sickle cell anemia can be a lethal disease if proper treatment is not available.

Malaria is a disease that kills hundreds of thousands of people every year. More people die from malaria than sickle cell anemia worldwide. In malaria infested countries, those people who are carriers of the sickle cell allele (Aa) are provided a resistance to malaria, and therefore, are more likely to survive

d. organisms have cells with different shapes and functions.