To study some effects of alcohol consumption, Dr. Chu tested the physical coordination skills of 21-year-old men who had just drunk either 4, 2, or 0 ounces of alcohol. In this study, the independent variable consisted of:

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.

The body is protected against harmful flu viruses by

The negative impacts of nonnative species generally outweigh the positive impacts