Ok. Here's
where you learn how amoebae work. Although amoebae are
the simplest creatures on earth, they still have many
body parts. The outer skin of an amoeba is called the
membrane, and the inner stuff is called the cytoplasm.
The membrane is used for protecting the amoeba, as
well as holding it all together, but water can still
pass through it. The amoeba is able to breathe using
the oxygen that is in the water. The word cytoplasm
means, 'soft cell stuff.' The cytoplasm is like jelly.
The gel, which is the outer part of the cytoplasm, is
a lot harder than the stuff on the inside, which is
called sol. When the amoeba moves, the gel turns into
the sol, and the sol turns into the gel. It's always
changing. So what's the difference between gel and
sol? Sol is more runny, but it has a lot of important
stuff inside. Sort of like... a soup. You have all
that broth, with the beef and potatoes and things like
that. Does that help you to picture it? The sol is as
important to an amoeba as a heart and lungs are
important to us. But, the amoeba doesn't have heart
and organs, like we do. The body of an amoeba is too
simple for things like that. Instead, it has these
things called organelles, which means, 'little
organs.' These organelles float around in the
cytoplasm. The largest organelle is the nucleus. The
amoeba proteus has one nucleus. The nucleus is the
command center. The control station. The mother. The
heart. Well, not the heart. But, the nucleus is not
like a brain. The amoeba doesn't think and learn as we
do. It doesn't plan ahead when it will split, or
something like that. Its motions and actions are
determined by what goes on around it. It doesn't
think. It reacts.
Try this. Find your
sibling. If you have no siblings, any small, annoying
neighbor will do. Throw a baseball at him or her. Be
sure to not actually hit the target, or it will hurt
them. But watch as you throw the ball, how they duck
or crouch, instantly, without thinking. That's how an
amoeba's nucleus works. Ok. Back to other
stuff.
The nucleus is
surrounded with something called a nuclear membrane.
This protects it. The food that amoeba's digest are
stored in food vacuoles. There is something called a
contractile vacuole, which drains the water that gets
inside the amoeba. Every few seconds, something called
a hyaline cap appears inside the amoeba, which looks
like an area with no gel or sol inside of it. The
hyaline cap soon disappears, because gel and sol flow
into it. If you view a picture of an amoeba, you would
see that it is blurry. This is not because it's so
small that it looks weird. It is because the sol and
gel are moving so fast throughout the amoeba's
body.
Here's some more
detail on the contractile vacuole. Contractile vacuole
means, 'a small space that can shrink.' The
contractile vacuole is always in the back of an
amoeba. It travels through the sol, collecting water,
and then delivers it to the membrane where it exits
the body. When the contractile vacuole gathers water,
it grows larger. When it empties, it shrinks back to
normal size. After it is done cycling throughout the
amoeba's body, it repeats the process. The vacuole is
emptied every few minutes.
The amoeba is a
strange creature. It has no eyes, nose, ears, or
mouth. Yet, it can still sense things. They know when
they are floating or not. If the amoeba encounters an
obstacle, it will try to go over it. If that doesn't
work, it will try to go around it. If this still
doesn't work, it will go somewhere else, since the
amoeba doesn't plan ahead where it wants to go. If an
amoeba finds either something sharp, a crystal of
salt, or some type of acid, it will back away as fast
as possible. And, yes, I am aware that I said all of
this on the movement page, but I think this could fall
into both categories.
The amoeba hates
light, especially blue light. If the amoeba is exposed
to any light, it will find a shadow, and make itself
in the shape of that shadow. But, instead of staying
in the shadow, it will move around in circles, like a
dog chasing its tail. If an amoeba is exposed to light
with no shadows, it will stop moving. It will pull in
all its false feet and empty out all food and water
inside its body, and shape itself into a ball. If
nothing else happens for a few minutes, it will move
away. Scientist don't know how amoebae can sense
light, without a brain or nerves.
Whew! Down below is
a picture of an amoeba. See if you can identify the
nucleus and the contractile vacuole.
