Answer:
SA node
Explanation:
The SA node (called the pacemaker of the heart) sends out an electrical impulse. The upper heart chambers (atria) contract. The AV node sends an impulse into the ventricles. The lower heart chambers (ventricles) contract or pump.
The way glass traps heat in a greenhouse
Population age structure is a summary of the number of individuals of each age in the population. An example is, In 2002, 30% of the worlds population was under 15 years old. <span />
Coriolis Effect is defined as an effect whereby a mass moving in a rotating system experiences a force which <span>act perpendicular to the direction of motion and to the axis of its rotation.</span>