Since the other answer got deleted, i'll just answer it for you.
a sinoatrial node is the main pacemaker that begins each heartbeat located in the junctions of superior vena cava and the right atrium. It signals from the node that spread through the atria and determines the heart rates.
Mitochondria produce ATP, energy that is vital in aerobic cells. Therefore, I believe this is why they can be considered as power plants.
The cell is the basic structural and functional unit of life
Orientation behaviors usually determine the type of environment that an animal will prefer to live. Animal orientation behavior is a complex process which determine how an animal receives information from the external world and how it responds to it.
DNA polymerase is one way to directly correct DNA replication errors. It checks the base that has been freshly supplied ahead of the succeding base so a corretion can be done. If it cannot proofread, an outcome of mutation is greatly possible which is considered as an i
