How are there microorganisms on every surface imaginable on Earth? How did they get there in the first place?
Wind or water can disperse microorganisms anywhere on the planet very easily as they are light and take almost no effort to move from place to place.
There aren’t. There are many surfaces on earth with no microorganisms on them. It’s just that there are microorganisms on human skin, so everything that we come into contact with as humans will end up with microorganisms on it because we, or someone else, will at some point touch it. Course, leave it long enough and they’ll die, so there’ll only be the dead remains of microorganisms on many of those surfaces.
They were there long before humans were a thing.
Microorganisms have existed for about 4 billion years, humans for less than a million. They might be small and slow, but that gives them plenty of time to make the rounds. It helps when you are tiny enough to live in airborne water droplets.
Microbes are subject to, theoretically, the same evolutionary pressures that bigger animals are, so after generations of a microbe being exposed to a specific selection pressure (say, high heat) they will start to develop adaptations which enable them to survive via random mutation, and the ones which are unspecialized die off. That community will usually become better and better at surviving a given environment over time due to natural selection. A plethora of hyperspecialized microorganisms exist in a wide variety of environments, from undersea hydrothermal vents to sub-zero ocean water to acid mine drainage. Then there are microbes which exist only within our gut, only on our skin, etc. Basically, they exist in a wide variety of places because they are evolutionarily specialized to do so.
How they got there is a different question. A lot of scientists suggest that life first evolved near hydrothermal vents at the sea floor due to suitable chemical and thermal dynamics. (constant infux of thermal energy allowed for ‘chemical life’ to develop maybe in the form of complex enzymes which managed to begin replicating themselves, then biological life was a short jump from that when RNA got involved. Then DNA evolved.) Other people suggest maybe microbial life came here from outer space, maybe when a meteor with water on it crashed.
It’s been a while since my environmental microbiology class so je m’excuse if there are any errors, please correct me.
Attempted 5-year-old explanation:
Microbes evolve different body parts to help them survive in crazy environments, like places where it is very hot or where it is very cold or even in acid. Some people think that the first microbes were born at the bottom of the sea where there is very hot water being pumped from inside the earth. That hot water gave energy so that different chemicals could play with each other and turn into different things until it started turning into something ALMOST that was alive. Then that almost-alive thing developed into something that was the first microbe, which split to make other microbes until there was a lot of them.
Well.. First things first:
There is ofcourse not every microorganism on every surface as they are indeed specialized and sometimes they compete for the same resources and sometimes they don’t.
But a lot of the microorganisms are adaptive and allow for various living conditions.
So now, Microorganisms exist for a very long time. And a lot of them are motile (meaning they can move on their own). They are small so the distance they travel is small too but over time they will spread. Additionally whenever a creature picks some microorganisms up, say through digging through the ground, they will also “drop” some at the next location and if the living conditions are suitable the microorganisms will start to spread there too.
There is also a possibility for bacteria to form spores where they encapsule themselves to be protected from the environment and when the conditions are better they can revert to their “living” status (can last 10+y).