Which of the following is a principle of natural selection? a) most organisms are infertile or produce nonviable offspring. b) members of a species are genetically identical. c) variations are acquired during an individual's lifetime and so are not passed to offspring. d) variations allow individuals to survive and reproduce better than members who lack these variations.

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.

What is the most abundant vertebrate on earth?

4. if a cell is placed inside a solution that has a higher concentration of solute than on the inside of the cell, what can be said about the movement of water? a. water will move out of the cell, causing it to shrivel. b. water will move in and out of the cell at the same rate. c. water will move out of the cell, causing it to swell. d. water will move into the cell, causing it to swell.