When you read books or watch movies about Zombies they often bleed and ooze out weird substances. Sometimes it is red like our own blood and other times it can be green or a variety of other colors. Even if the video games such effects are part of the fun of being able to play them.
It does tend to make one thing about the biology of a Zombie though. If they were to be actually walking around on Earth how would their bodies function? First, they would have to have some brain function and some overall nerve functions. This would explain how they would be able to walk around and how they would be able to know what to do instinctively to survive as a Zombie.
They would have nerve endings too so that they would be able to feel pain. After all the demise of the Zombies is just as important as them living. The often give out great sounds of pain when they are being destroyed.
The means of how a Zombie is able to turn others into what they are has to be part of their biology too. This is believed to be through various pathogens. For example when humans pass along a cold virus or flu virus it is due to the pathogens that go from one person to the next. The same would have to be true of what the Zombies are passing from themselves to others and that is how the infection would occur.
Most Zombies consume human flesh and so they would need a very defined system of digestion. With Vampires it would be different as they consume blood and not flesh. Still their digestion system would have to be set up for that process to take place. Digestion always has to allow for the living or undead to be able to get nutrients from what they take in. It would be fascinating though to see the digestive workings of any Zombie if they were real.
Why is it that the Zombie profile is usually of something that is rotting and decomposing? That would definitely signify that with their biology there is something that just isn’t living. Identifying what would be part of functional living and what isn’t would be very hard to explain though. Most Zombie books and movies don’t go into those details as they don’t want to get into a tangled mess trying to explore all of that!