_6. every chemical reaction always involves which of the following?
a. a change in the state of matter.
c. a combination of compounds
b. a transfer of electrons between atoms d. some transfer of energy solid

How are rocks that cooled within magma chambers found on earth’s surface today? they are pushed up by magma under earth’s surface. they are revealed by erosion of earth’s surface over time. they are pushed to earth’s surface because of their larger size. they are revealed at earth’s surface due to their low density.

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.

Which event would lead to primary succession of a forest?