The earth is composed of three different chemical layers core mantle and crust the formation of these layers was from a process called

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.

Describe the two types of vascular tissue

Using meiosis, the sporophyte produces spores that are .