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Archaea 

Bacteria

Eukaryota

During diastole the atria and ventricles are relaxed. The atrioventricular valves are open and the semilunar valves are closed. Deoxygenated blood enters the right atrium from the venae cavae and oxygenat...

Electrical impulses from the SAN (sinoatrial node) spread across the atria walls to cause contraction. The impulses then pass to the ventricles via the AVN (atrioventricular node) after a short delay to a...

Firstly it is always good to relate such a concept with an example that is easily remembered and therefore easily applied. Alleles refer to alternate forms of the same gene, which code for a particular tr...

An action potential is the signal neurons use to communicate with each other. It is caused by the rapid opening of sodium channels and influx of sodium ions. Because at rest the inside of the neuron is ne...