Primary producers are organisms that a. rely on other organisms for their energy and food supply.
b. consume plant and animal remains and other dead matter.
c. are the first producers of energy rich com-pounds that can be used later by other organisms

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.

Explain how the number of similarities between the embryos from early stage to late stage is used as evidence of a common ancestry

When new rock is added to an oceanic ridge, the magnetized strips on either side of the ridge are evidence of sea-floor spreading. this is because the rocks on the two sides of the ridge o are equal in width and in polarity are polar opposites oare magnetized vary in width but are equal in polarity