The contracting and relaxing of muscle is regulated by the amount of calcium present in the cells of muscle fibers. these cells must be able to move the calcium ions from areas with low concentrations to areas with high concentrations. what process would be necessary for this movement to occur?

Which of the following is not a defining characteristic of plants?

What element does susan b. anthony include in this passage to strengthen her argument?

Astudent reads the following text in a science book: scientific evidence tells us that the cause of earths four seasons is the tilt of earth as it revolves around the sound the student is instructed to illustrate this information in a science book. how will the student illustrate winter in the northern hemisphere? a. earths northern hemisphere will tilt away from the sun. b. earths northern hemisphere will tilt toward the sun. c. earths orbit will be farther away than from the sun d. earths southern hemisphere will tilt away from the sun.