Help pleaze im taking an exam

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Each pair of clay balls represents two planetesimals. if each planetesimal is composed of the same material and is separated he the same distance, which pair experiences the frayed gravitational attraction?

In a cross between individuals of a species of tropical fish, all of the male offspring have long tail fins, and none of the females possess the trait. mating two of the f1 fish fails to produce females with the trait. explain the inheritance pattern of the trait.