What is true of an atom’s nucleus? it is positively charged and takes up most of the atom’s space. it is negatively charged and takes up most of the atom’s space. it is positively charged and includes most of the atom’s mass. it is negatively charged and includes most of the atom’s mass.

Match the following terms describing electrical events with the correct phases of the cardiac cycle. the ventricular muscle cells depolarize at the start of this phase. during this phase, na+ entry through the funny channels causes the pacemaker potential of sa nodal cells to gradually become less negative until it reaches threshold. the ventricular muscle cells repolarize right before this phase. the cytosolic concentration of calcium in the contractile cells of the ventricle is highest during this phase. a. isovolumetric relaxation b. ventricular ejection c. isovolumetric contraction d. ventricular filling

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?

Explain how paleontologists use trilobite fossils as index fossils for various geologic time periods.