How did a change in the environment affect life for people in the American Southwest?
A. A lack of rain may have caused people to leave the region.
B. The desert climate forced farmers to build terraces.
C. Access to waterways led to the creation of canals.
D. A series of earthquakes made farming impossible.

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 image shows labeled organelles that are present only in plant cells?

Astudent is looking through a microscope at some cells of an onion root tip. many of these cells are undergoing division since the root tip grows quickly and requires more cells. which cell most recently underwent metaphase? w x y z