Explain why the structure of mitochondria and ribosomes was not well understood before the development of the electron microscope, HELP PLEASE

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

Select the correct answer. which term do biologists use to describe the average number of individuals of a species per unit area? a. carrying capacity b. population density c. minimal viable population d. survivability curve

An animal cell (left) and a plant cell (right) are shown.which organelle, labeled x in the diagram, is found in both plant and animal cells?