The Littlest Organisms
Let's study the wee ones of the world known as the microbes or the microorganisms. If you spend your life studying them, you would be amicrobiologist. These are the smallest of the small and the simplest of the simple. Some of them, like viruses, may not even be alive as we currently define life.
What is a Microbe?
What makes a microbe? We suppose you need a microscope to see them. That's about it. There is a huge variety of creatures in this section. They can work alone or in colonies. They can help you or hurt you. Most important fact is that they make up the largest number of living organisms on the planet. It helps to be that small. It's not millions, billions, or trillions. There are trillions of trillions of trillions of microbes around the Earth. Maybe more.
Calling all Microscopes
As with all of science, discovery in biology is a huge thing. While microbes like bacteria, fungi, some algae, and protozoa have always existed, scientists did not always know they were there. They may have seen amushroom here or there, but there were hundreds of thousands of species to be discovered.
It took one invention to change the way we see the world of microbes - the microscope. In 1673, Anton von Leeuwenhoek put a couple of lenses together and was able to see a completely new world. He made the first microscope. It wasn't that impressive, but it started a whole history of exploration. More important to us, scientists were eventually able to discover the cause and cure of many diseases.
Too Many to Count, Too Small to Find
We'll give the big overview on the variety of microorganisms here. There is no simple explanation of a microbe besides the fact that they are small. The list goes on. Just remember that there is a lot of variety going on here.
They can be heterotrophic or autotrophic. These two terms mean they either eat other things (hetero) or make food for themselves (auto). Think about it this way: plants are autotrophic and animals are heterotrophic.
They can be solitary or colonial. A protozoan like an amoeba might spend its whole life alone, cruising through the water. Others, like fungi, work together in colonies to help each other survive.
They can reproduce sexually or asexually. Sometimes the DNA of two microbes mixes and a new one is created (sexual reproduction). Sometimes a microbe splits into two identical pieces by itself (asexual reproduction).
Prokaryotes - Missing a Nucleus
If you're looking to learn about cells with a nucleus, this is the wrong place.Prokaryotes do not have an organized nucleus. Their DNA is kind of floating around the cell. It's clumped up, but not inside of a nucleus. If you want to learn about cells with a nucleus, look for information on eukaryotes. And, once again, a prokaryote is a single cell or organisms that does NOT have organized nuclei.
Can You Exist Without a Nucleus?
You can't, but they can. What can you do without a nucleus? You can do a whole lot. Most prokaryotes are bacteria and bacteria can do amazing things. Although they are very simple organisms, they are found everywhere on the planet. Some scientists even think that they may be found on other planets (maybe even Mars). Some places you can find bacteria every day are in your intestines, a cup of natural yogurt, or a bakery. Prokaryotes are the simplest of simple organisms. Here's the checklist.
(1) Prokaryotes have no organized nucleus. Like we said, the DNA is clumped in an area but there is no organized nucleus with a membrane.
(2) Prokaryotes do not usually have any organelles. They will probably have ribosomes inside of their cells, but ribosomes are not technically considered organelles. No chloroplasts. No mitochondria. No nucleus. Not much at all.
(3) Prokaryotes are very small. Because they don't have all of the normal cell machinery, they are limited in size. As always in biology, there are exceptions, but generally, prokaryotes are very small (compared to other cells). Mind you, compared to a virus they are big, but next to an amoeba, tiny.
(4) Prokaryotes don't have mitosis or meiosis like other cells. Scientists don't really have a good way of describing how they duplicate, but it's not through normal means. Check out the bacteria tutorial to get an idea.
