Why are sea otters considered a keystone species? Why are they important?

Spring tides, when the high tides are at their highest and low tides at their lowest. what is it about these positions that causes these high and low tides?

Every early childhood education program should develop a

Membrane vesicles containing an internal sodium chloride (nacl) concentration of 0.14 m are placed into separate beakers each containing a different solution. the first beaker contains 0.14 m sucrose, while the second beaker contains 0.14 m calcium chloride (cacl2). the temperature is 25°c. what is the solute potential inside the vesicles, expressed in units of mpa?