How can farmers keep topsoil on their land? check all that apply. a. close their gates b. keep plants growing c. plant trees to shield fields from the wind d. do not plow when extremely heavy rains are expected?

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 of the following is not a defining characteristic of plants?

Nerve cells are specialized to respond to stimulitrue or false?