Answer:
Answer is Sinoatrial node, SA.
Explanation:
The sinoatrial node, SA, is known to be a group of cells which are found at the top of the heart.
The electrical signal that is initiated by the sinoatrial node bring about or stimulates the atria and then the ventricle of the heart.
It should be noted that, the sinoatrial node are regarded as the pacemaker cells.
Answer:
4 mass extinctions
Explanation:
as there are huge drops in the graphs
at 440,390,260,50
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<span>Newton first law is called inertia, or the force an object has to resist unbalanced forces that are placed upon it. The more mass an object has, the more inertia an object has. The less mass an object has, the less inertia an object has.</span>
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