How are hills beneficial to humans ?

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.

Astudent observes a star from two positions of earth in its orbit, in summer and winter, and measures the change in the position of the star. which of these can be best calculated by this method?

The many volcanoes located along the edge of the pacific ocean make up the ring of fire. how does subduction play a role in the volcanic activity in the ring of fire?