The is the very small, dense center of an atom.

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

Some species of wasps are social. the queen starts a colony from scratch each spring. she builds a small nest, and lays and raises a group of female workers. the workers enlarge the nest while the queen continues to lay eggs. unfertilized eggs become males that mate with newly hatched females. all of the wasps except the newly fertilized females die by the summer. which best describes this behavior? a)it is beneficial only to the males that do not fertilize eggs. b)it is beneficial only to the female workers that are not fertilized. c)it is beneficial to each one of the individual colony members. d)it is beneficial to the whole species, but not to all of the individual members.

Abeaker of water was heated and then placed on a bench in the laboratory. the water cooled until it was the same temperature as the air in the laboratory. which of these explains the mechanism by which the water cooled? a. heat energy was transferred from the water to the air. b. water molecules from the water formed warm water currents. c. the water molecules absorbed energy from the molecules in the air. d. the water released radiation until it contained no heat energy.