There are a whole lot of living things crawling, oozing, scuttling or standing around on planet Earth. Scientists think it's important for us to get to know our neighbors. To make this easier, the world of living things into five kingdoms:
There are also two groups of oddities which (according to most scientists) aren't exactly living, but are close enough for us to be interested.
Below are short descriptions of each of these kingdoms.
If it has one cell but no nucleus, it's a moneran. You're more familiar with calling these guys bacteria or germs. Although you can't see them with the naked eye (is there a clothed eye?) they are all around you. And in you and on you and through you too. You can't go anywhere on earth without running into Monerans. There are even little bacteria on the mouse you've been clicking. Don't panic though, most are harmless.
Most protists have only one cell, and all of them have a nucleus. Other than that, you'll find that this is a diverse kingdom. Some protists are a whole lot like plants, some have animal behavior, and some have both. These weird little guys have a world of their own, usually under a microscope or in a nearby pond. Protists are commonly called protozoans or algae. No, Algebra is something totally different. Algae is seaweed. Protozoa are animal-like creatures. They're handy to know if you're a regular reader of The Far Side.
Plants are easy. Almost anyone can pick a plant out of a police lineup. These handy organisms make food. And not only for themselves, but they make food for everything else too! These busy critters can turn sunlight into sugars, and that is a handy trick indeed. Hug a plant today!
Mmmmm...fungus. Fungi are handy critters to have around. Most are decomposers, which means they feed on decaying matter. Now THERE is something to think about when sinking your teeth into a mushroom pizza. Or a slice of bread. Yeasts are fungi too. Fungi can be very handy, although some can cause real problems. Athlete's foot is a fungus.
We are most familiar with the animal kingdom because we're a part of it. But this is a pretty big kingdom. It has everything in it from worms to walrusses, from sponges to salamanders, and from beetles to The Beatles. Look around you and you might find animals hiding everywhere. There may be insects flying around the room. There may be little worms in the soil of a potted plant. There may be a rhino under the bed. You never can be too sure.
Viruses don't exactly qualify as living things. They don't do a whole lot other than reproduce. They are little more than a bunch of DNA or RNA enclosed in protein, but if they get into your cells, they can do anything from give you the sniffles to kill you. Viruses don't live outside of living cells. They just sit around and wait for an opportunity to invade and conquer. When they do invade, they turn a cell into a little virus-making factory.
Most scientists would agree that prions are not alive. They are only proteins and have no DNA. So why are they even mentioned here? They can reproduce - so to speak. There are two types of prions. One looks like a spiral, and the other is folded like a fan. The pleated prion can cause the spiral prions to change their shapes, making more and more of the folded variety. It is believed that this causes mad cow disease, and other diseases which are similar.
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