Amoeba





Amoeba 2794
Photo by: Steve Young

An amoeba (pronounced uh-MEE-buh) is any of several tiny, one-celled protozoa in the phylum (or primary division of the animal kingdom) Sarcodina. Amoebas live in freshwater and salt water, in soil, and as parasites in moist body parts of animals. They are composed of cytoplasm (cellular fluid) divided into two parts: a thin, clear, gel-like outer layer that acts as a membrane (ectoplasm); and an inner, more watery grainy mass (endoplasm) containing structures called organelles. Amoebas may have one or more nuclei, depending upon the species.

The word amoeba comes from a Greek word meaning "to change." The amoeba moves by continually changing its body shape, forming extensions called pseudopods (false feet) into which its body then flows. The pseudopods also are used to surround and capture food—mainly bacteria, algae, and other protozoa—from the surrounding water. An opening in the membrane allows the food particles, along with drops of water, to enter the cell, where they are enclosed in bubblelike chambers called food vacuoles. There the food is digested by enzymes and absorbed into the cell. The food vacuoles then disappear. Liquid wastes are expelled through the membrane.

Water from the surrounding environment flows through the amoeba's ectoplasm by a process called osmosis. When too much water accumulates in the cell, the excess is enclosed in a structure called a contractile vacuole and squirted back out through the cell membrane. The membrane also allows oxygen to pass into the cell and carbon dioxide to pass out.

The amoeba usually reproduces asexually by a process called binary fission (splitting in two), in which the cytoplasm simply pinches in half

Amoeba proteus. (Reproduced by permission of Photo Researchers, Inc.)
Amoeba proteus. (Reproduced by permission of
Photo Researchers, Inc.
)

and pulls apart to form two identical organisms (daughter cells). This occurs after the parent amoeba's genetic (hereditary) material, contained in the nucleus, is replicated and the nucleus divides (a process known as mitosis). Thus, the hereditary material is identical in the two daughter cells. If an amoeba is cut in two, the half that contains the nucleus can survive and form new cytoplasm. The half without a nucleus soon dies. This demonstrates the importance of the nucleus in reproduction.

Some amoebas protect their bodies by covering themselves with sand grains. Others secrete a hardened shell that forms around them that has a mouthlike opening through which they extend their pseudopods. Certain relatives of the amoeba have whiplike organs of locomotion called flagella instead of pseudopods. When water or food is scarce, some amoebas respond by rolling into a ball and secreting a protective body covering called a cyst membrane. They exist in cyst form until conditions are more favorable for survival outside.

Words to Know

Asexual reproduction: Any reproductive process that does not involve the union of two individuals in the exchange of genetic material.

Cytoplasm: The semifluid substance of a cell containing organelles and enclosed by the cell membrane.

Organelle: A functional structure within the cytoplasm of a cell, usually enclosed by its own membrane.

Osmosis: The movement of water across a semipermeable membrane from an area of its greater concentration to an area of its lesser concentration.

Protozoan: A single-celled, animal-like organism.

Pseudopod: From pseudo, meaning "false," and pod, meaning "foot"; a temporary extension from a cell used in movement and food capture.

Some common species of amoebas feed on decaying matter at the bottom of freshwater streams and stagnant ponds. The best-known of these, Amoeba proteus, is used for teaching and cell biology research. Parasitic species include Entamoeba coli, which resides harmlessly in human intestines, and Entamoeba histolytica, which is found in places where sanitation is poor and is carried by polluted water and sewage. Infection with Entamoeba histolytica causes a serious intestinal disease called amoebic dysentery, marked by severe diarrhea, fever, and dehydration.

[ See also Cell ; Protozoa ; Reproduction ]



User Contributions:

Curtis
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Jul 6, 2009 @ 3:15 pm
Thanks for this article about Amoeba's you have educated me about Amoeba's alot.Thank you.
Donna Hart
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Oct 10, 2009 @ 9:21 pm
This was great information for my Biology class. We have to fill out a lab report about Ameoba and Anabaena. If only I could find information on Anabaena. Thank you.
Amelia
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Oct 21, 2009 @ 8:08 am
Thank god that someone is actaully able to give out decent information! this is the exact information i desperatly needed for my science project. thank-you!!
lavina
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Oct 21, 2009 @ 6:18 pm
nice i would like to learn more about amoeba, would u guys help me to understand
Musawer
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Dec 11, 2009 @ 2:02 am
Thanks 4 this article about amoeba i would like to learn and thanks
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Mar 18, 2010 @ 8:08 am
thanks for the page we needed to learn the amoebas reproduction thanks
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May 14, 2010 @ 5:05 am
so much thanx to explain amoeba in such a simple way.i like it and agian thanx
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Jul 16, 2010 @ 2:14 pm
Thank you so much for this interisting site. You did a great job in explaining the amoeba in a simple way. It helps a lot.
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Jul 17, 2010 @ 12:00 am
Are any of the amoeba species capable of migrating to different organs in the body, such
as the liver, spleen or lungs? Thank you very much!
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Sep 1, 2010 @ 11:11 am
I saw a disfigured pic of a white males head under the title amoeba protoza, is this some type of rare condition? if so could someone point me in the right direction to learn more about this?
thank you...tom
maaza
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Oct 22, 2010 @ 1:13 pm
it is nice to read such an incredable point about amoeba.but I have a question,about bacteria,that is amoeba agravate or getting worth when a person has an amoeba cist eats some types of food like vegitables,milk and milk products,fruits ..etc?
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Oct 28, 2010 @ 11:11 am
Just learning that my Husbnd has an Amoeba in his intestines.He hasnt been out of the Country.His stomach problems have kept him home for a number of years.Any Idea as to how this could have been contacted.I did wonder if his having quite a few Colonascopy;s in a very busy office if this could be the cause.
marco
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Nov 12, 2010 @ 2:14 pm
Thanks alot for the article.It helped me in my biology project
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Dec 26, 2010 @ 11:11 am
This is a very good article guys, thanx alot. Would someone tell me about amoeba found in fruits? And its cure.
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Mar 30, 2011 @ 1:01 am
thank you so much, you helped me to understand Amoeba very well.
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Jun 1, 2011 @ 6:18 pm
this is an amazing article and it helped me with my brochure for biology
matt bergeron
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Jun 6, 2011 @ 8:08 am
this artcal helped me very much and it helped by giving me information i didnt know even though i studied it. Thank you very much.
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Jun 8, 2011 @ 4:04 am
That is very interesting and helped alot with my biology class. Thanks guys
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Jun 16, 2011 @ 2:14 pm
Hi! I feel the hunger of knowing more about AMOEBA.I wanna know where & when we can get this & also, how to avoid having this parasites! thank you po!
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Jul 16, 2011 @ 8:08 am
Thanks guys...I hope you'll continue and develop more...God bless & take care...Wishing you guys peace of mind : )
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Jul 31, 2011 @ 6:06 am
May I know which part of the cell helps in the movement of the amoeba? Please explain to me as i don't really understand, thank you.
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Aug 14, 2011 @ 5:05 am
what are the diseases it cause?and where does it live.and how does it reproduced?
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Aug 17, 2011 @ 6:18 pm
everyone is in the water, everyone goes to the pools each year during the summer, how do you avoid them in the united states
Petro
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Oct 7, 2011 @ 2:02 am
Thank you for this informative article, never too old to learn, that's for sure. Can you please tell me more about the amoeba parasite, what symptoms it causes, what the effect on the body and specific organs and one's overall wellbeing can be, how do you get rid of it
broby
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Oct 28, 2011 @ 8:08 am
Thanks for the info. im doing a project and it really helps
cheyenne
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Oct 28, 2011 @ 10:10 am
thank you for this information. I really enjoyed reading this site and it helped alot with my project again thanks alot.
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Oct 30, 2011 @ 4:16 pm
Thanks for the great info! It was just the information I needed layed out in an understandable form! Thanks alot!
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Nov 7, 2011 @ 12:12 pm
Just what I needed to answer questions on my assignment. Thanks for this!
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Nov 13, 2011 @ 9:09 am
This is so cool!!!and just what i needed, i now know more about "ameba".thank$ for this.
andrea
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Nov 29, 2011 @ 7:19 pm
thank u for this websiit that help other persons for ther work
ankita kalra
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Dec 28, 2011 @ 8:08 am
THNKS FOR SUCH WEBSITE WE CAN EASILY DO OUR WORK PROPERLY
vanessa
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Jan 12, 2012 @ 5:17 pm
thx it helped me alot for my science class this is an awesome website i would prbably come here for information :)
Jordan
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Jan 28, 2012 @ 6:18 pm
Thanks a lot! This website has helped me with my microorganism report!

Thanks Again!
Alyssa
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Feb 1, 2012 @ 4:16 pm
I really enjoyed this piece on amoeba's it has gave me a lot of good detail for my amoeba poster and has really helped this piece has nice pictures and very good wording nice job i give this piece 5 stars :)
justin
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May 8, 2012 @ 10:10 am
thank you four have the corret and exact information i needed for my projet
maame
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Aug 5, 2012 @ 6:18 pm
THANKS FOR THE ARTICLE. ITS REALLY GREAT. AM GOING TO GET AN A IN MY BIOLOGY PROJECT.
Ruth
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Sep 22, 2012 @ 12:12 pm
Is anybody there to answer questions about the amoeba? I see many questions but no one answers.
Purnima
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Oct 5, 2012 @ 12:12 pm
Thanks for this article.This is all what i need for my biology activity.
Fabian1
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Oct 26, 2012 @ 11:23 pm
Thanks to a brilliant effort in publishing your article. One can be more informative as this. There are many things I can know only after reading your wonderful article
racheal
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Nov 24, 2012 @ 8:08 am
I REALLY LEARNT ENOUNGH FROM YOUR ARTICLE.THANKS A LOT
ceciulbravo khuntapay
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Dec 11, 2012 @ 6:06 am
THANKS ALOT.IT HELP ME ALOT TO KNPW ABOUT AMEOBA DISEASE.IVE LEARNED HOW TO PREVENT AND AVOID THIS DISEASE.
fuseini sulemana
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Jan 19, 2013 @ 9:09 am
actually im very greatful for this page...i wont know where else to find an explicit explanation on amoeba..thanks alot
Umar alhassan
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Jan 28, 2013 @ 2:14 pm
Is, this amoeba aquatic or teresterial habitat and are they causing any disease to us, if they are. What is the name of the disease?
rodgers kalengo
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Feb 24, 2013 @ 3:03 am
Thanks a lot ladies and gentlemen l couldn,t know the amoeba but now l see.
katrina
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May 8, 2013 @ 12:12 pm
its very goog good job i salute you your diagram is very nice
jennifer
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May 15, 2013 @ 8:08 am
THE AMOEBA DIAGRAM AS HELPED ME SO MUCH,THANKS A LOT.WITH THIS I KNOW I WILL GET 'A'IN BIOLOGY
sleep less
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Oct 9, 2013 @ 9:09 am
what is a amoebas specialized cell parts yes the is for a class graed
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Oct 10, 2013 @ 3:03 am
Great work! However, I needed to find out what happened when cyanide was added to amoebas water and why they did ;(
Yanmarie
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Oct 14, 2013 @ 5:17 pm
Do they have other type of Amieba ?? And by the way thank you very much for teaching this to me and to others !!
yo
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Nov 12, 2013 @ 9:09 am
what is amoebas predators can anyone tell me please i need to know for science
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Feb 24, 2014 @ 11:23 pm
Why Amoeba needs division when it can live as single?
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Feb 28, 2014 @ 11:23 pm
can you please tell me if amoeba does not have any organs and systems then how does it stays alive?
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Mar 6, 2014 @ 1:13 pm
Thank you so very much for xplaining amoeba in a short form.
alecia
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May 22, 2014 @ 5:17 pm
Thank you for giving in more information about amoeba...I've learnt more about amoeba & it gets to my attention that it also causes diseases. Thank for the informaton given.
precious
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Jun 13, 2014 @ 6:06 am
WHAT'S THE USE OF AMOEBA IN ECOSYSTEM.BIOLOGY is a very broad subject am running from.

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