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What is Paramecium?

S. Mithra
S. Mithra

A paramecium is a unicellular organism belonging to the kingdom Protista, so it isn't exactly a plant or an animal. The organism can digest food, move through water by propelling itself with cilia, and reproduce. As one of the oldest organisms on earth, it has evolved and developed very simple methods of defense, genetic exchange, and mobility.

There are several different species of paramecia, but all are ciliate protozoa. This means they use cilia to swim through water, and their one complex cell, a eukaryote, conducts all of the organism's basic functions. It doesn't divide labor between different tissues or cells like an animal. Instead, each paramecium is capable of an aerobic exchange, similar to breathing, reproducing asexually, ingesting nutrients, and expelling waste.

Physical Appearance


With good vision, it is possible to just make out the speck of a paramecium, since they are about .02 inches (.5 mm) long. They're better viewed under a microscope, where a slipper or kidney shaped cell can be seen. Lining the outside of its membrane are tiny, beating hairs called cilia. Cilia move in conjunction, like a line of oars on a ship, to move the paramecium through liquid. The eukaryote is even smart enough to navigate around obstacles and towards food.

Three Paramecium caudatum.
Three Paramecium caudatum.

When a paramecium encounters food, it swivels to move the food into its gullet. The gullet is a small opening, like a mouth. It's lined with other cilia to help "swallow" the bits of organic or decaying matter it eats, such as other unicellular organisms or bacteria. The food will continue down the gullet to get stored in food vacuoles until the cell needs energy.

Paramecium are better viewed under a microscope.
Paramecium are better viewed under a microscope.

It may also be possible to make out other rounded structures, called organelles, that sort of function like an animal's organs. One such organelle is the contractile vacuoles. The paramecium must keep osmotic equilibrium, which means the water pressure outside its skin and inside its body needs to be equal at all times. Contractile vacuoles pass water from inside the cell to outside, and vice versa.


Paramecium are celiated organisms.
Paramecium are celiated organisms.

Under most circumstances, paramecia reproduce by splitting themselves down the middle and giving each new organism half of the organelles. This is called binary fission, and is a simple form of asexual reproduction. Occasionally, a paramecium will meet another and exchange genetic material during a kind of primitive sexual reproduction. The membranous skins combine to make one giant paramecium, at which point the tiny micronuclei that hold all of the genetic material switch around. When it divides into four smaller paramecia, they now have new combinations of DNA.

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Discussion Comments


Why are they not animal or plant cells?


Does a Paramecium respond to light?


Can paramecium make you sick?


What do they smell like?


Could you give reasons about why a paramecium is unicellular?


Is the paramecium from the kingdom protista?


I was studying for my science test, it said something about paramecium. I thought to myself, "I've heard that word before." Then it hit me. I have a microscope, and it came with samples of random organisms, paramecium included. So I looked at the paramecium under the 40X lens, and saw hair-like strands floating back and forth. Super cool!


What's the definition of a gullet?


The actual function it does for the body is it eats bacteria. Therefore, it helps the body by killing the bad bacterias that can hurt your health. It also eats other small organisms such as algae and yeast.


This is all really nice info but where did the paramecium come from?


well paramecium don't have a "function", they are protozoans and can be used ecologically, how? in the sewage treatment, their cilia move the water, and in symbiosis with bacteria and fungi they can make less toxic sewage.


what's the structure of a paramecium?


paramecium is really cool to look under a microscope. it has all different kinds of colors like blue, green, red, yellow, pink and purple. i think paramecium are some of the coolest things to look at under a microscope.


what is the main function of paramecium?


What do paramecium do for the environment?


I really needed this for science. Thanks.


where do paramecium eat?


Does a paramecium produce methane gas?


what is the color of the paramecium?


What are the parts of the paramecium?


What is the actual function of the paramecium to the body?


Where did the paramecium come from??


I think this provides nutrients to the fish, and is probably only fed to small fish that do not need to eat large amounts of food, this is also part of a wild fishes diet. So this is also why:)


I've heard paramecium are used to feed fish. Why is this? What benefit does this have to the fish? What sort of fish is it feed to?

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    • Paramecia.
    • Three Paramecium caudatum.
      By: micro_photo
      Three Paramecium caudatum.
    • Paramecium are better viewed under a microscope.
      By: WavebreakMediaMicro
      Paramecium are better viewed under a microscope.
    • Paramecium are celiated organisms.
      By: Matthew Cole
      Paramecium are celiated organisms.
    • Although single-celled, paramecia can perform a variety of functions.
      By: snapgalleria
      Although single-celled, paramecia can perform a variety of functions.