The simplest and smallest life form known is
a. a virus
b. a bacterium
c. an archaean

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.

Why did mendel use pea plants in his experiments? a. they have no alleles. b. they are haploid organisms. c. they reproduce quickly. d. they are all male.

What causes eclipses? check all that apply. earth's rotation on its axis moon's shadow covering the sun earth's shadow covering the moon earth's orbit and moon's orbit occasionally aligning the moon and sun's gravity pulling in the same direction