Hydrologists know that the flow rate of a river is affected by the downhill slope and the width of the river’s channel. Consider an experiment in which scientists use model channels to test the following hypothesis: Water will flow more quickly through a narrower channel. What is the independent variable in this experiment, and what two variables should be controlled? Select the correct response.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.

when it is at an intermediate population density