If a scientist finds the remains of a plant between a rock layer that
contains 400 million-year-old Phacops fossils and a rock layer that contains
230 million-year-old Tropites fossils, how old could the plant fossil be?

What word is used to describe differences of individual organisms

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

Moving down the ramp from 6 meters to