Forewarning, I will try my best to cover a wide range of zombie varieties and cite the source of any specialized ones.
Zombies function solely from brain activity; as long as the brain is intact, they are able to move and attack. Zombies do not deliberately attack one another; usually proven wrong with the introduction of advanced or specialized zombies. Nerves are destroyed or blocked resulting in painless beings. Keen sense of sound, are able to detect wide range of sounds and immediately determine direction of origin.
Alright, similarities are few when I recall various interpretations of zombies.
Zombies are able to tirelessly move; requiring no nourishment or rest. Many series such as Left 4 Dead and 28 Days/Weeks show zombies that are able to run at their maximum speed for a seemingly unlimited time. Also from these series, zombies have advanced motor skills and are able to easily climb stairs and other obstacles fairly easily. Other series such as Shaun of the Dead or High school of the Dead represent the slow moving and clumsy zombie. These meander around and are somehow able to maintain standing position, even when knocked down. Surprisingly, they are able to climb stairs or avoid obstacles with little to no trouble. These speculations show that zombie brains still contain moderately advanced motor skills from previous life.
Infection to a host is usually caused by general attack; i.e., biting of the flesh. Once this has occurred, the victim has a few minutes at most before the transformation is complete. Based on this, the cause is most likely bacteria living in zombies' mouths. Contamination via saliva or other bodily fluids seems very possible, however is rarely seen in any depiction as this would result in near total and instant annihilation. Once infection occurs, the victim is no longer savory and thus no longer attacked. The need for new/uninfected flesh is the driving concern when dealing with zombies. From 28 Days/Weeks, it’s apparent that without human flesh to feast on, they will eventually starve and die causing mixed feelings on the best approach for the situation.
These are only a few possible analyses of zombies and I plan to delve more into this subject in future posts as I examine zombie origins and real world scenarios.