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.
Answer:
They all include an exchange of gases with the atmosphere.
The carbon, oxygen, and nitrogen cycles are biogeochemical cycles meaning the chemicals spend a portion during the cycle in living things ( bio) and a portion in the nonliving environment
Answer:
the correct answer is D
Explanation:
skin excretes sweat; lungs excrete carbon dioxide; kidneys excretes urine so these organs excrete metabolic waste because if you have learnt about the excretory system, you will come to know the process of excretion and how we humans excrete metabolic and toxic waste from the body.
