The amoeba
is a protozoan that belongs to the Kingdom Protista. The name ameba comes from the Greek word "amoibe", which means change. Amoeba is also spelled ameba. Protists are microscopic unicellular organisms that don't fit into
the other kingdoms. Some protists are
considered plant-like while others are considered animal-like. The animal-like protists are known as protozoans. The amoeba is considered an animal-like
protist because it moves and consumes its food. Protists are classified by how they move, some
have cilia or flagella, but the amoeba
has an unusual way of creeping along by stretching its cytoplasm into fingerlike
extensions called pseudopodia. The
word "pseudopodia" means "false
foot". Label the
pseudopodia. When looking at amoeba
under a microscope, an observer will note that no amoebas looks the same as any
other, the cell membrane is very flexible and allows for the amoeba to
change shape. Color and label the cell
membrane red. Amoebas live in ponds or
puddles, and can even live inside people.
There are two types of cytoplasm in the amoeba, the darker
cytoplasm toward the interior of the protozoan is called endoplasm, and
the clearer cytoplasm that is found near the cell membrane is called ectoplasm.
Color
and label the ectoplasm light blue and the endoplasm pink. By pushing the endoplasm toward the cell
membrane, the amoeba causes its body to extend and creep along. The amoeba also uses this method to consume
its food. The pseudopodia extend out and
wrap around a food particle in a process call phagocytosis. The food is
then engulfed into the amoeba and digested by the enzymes contained in the amoeba's lysosomes. As the food is
digested it exists in a structure called a food vacuole. Color and label the food vacuole
green.
Also visible in the amoeba is the nucleus,
which contains the amoeba's DNA. Color
and label the nucleus purple. In
order to reproduce the ameba goes through mitotic division, where the nucleus
duplicates its genetic material and the cytoplasm splits into two new daughter
cells, each identical to the original parent.
This method of reproduction is called binary fission. Another structure easily seen in the amoeba is
the contractile vacuole. This organelle pumps out excess
water so that the amoeba does not burst or lyse. Color and label the contractile
vacuole yellow.
During unfavorable conditions, the ameba
can create a cyst, this hard walled body can exist for a long period of
time until conditions become favorable again.
Label and color the cyst dark blue. At this point it opens up and the amoeba
emerges. Often cysts are created during
cold or dry periods where the ameba could not survive in its normal condition. Amoebas can cause disease. A common disease caused by the ameba is
called Amebic Dysentery. A person
becomes infected by drinking contaminated water. The ameba then upsets the person's digestive
system and causes cramps and diarrhea. A
person is most likely to be infected in countries where the water is not
filtered or purified.