What is a living organism?
My guess the ability to undergo life processes,
growth. It takes in some thing that converts
to material to sustain. With that, I looked up the definition.
1. An individual form of life, such as a plant, animal, bacterium, protist,
or fungus; a body made up of organs, organelles, or other parts that work
together to carry on the various processes of life.
Reading the definition, I'll drop my growth comment.
See, I was interested in ,"What's a rock?"
The small rock can't just be pieces if bigger rocks.
I might be wrong, but I felt a rock can accumulate layers, the atmosphere,
or surroundings, tack on. So, it could seem that rocks grow, but that won't
be sustain processes hence while appearing to grow, wouldn't be an organism.
This is an excellent question...it may seem simple but after being a
biologist for 30 years I am still not sure. Philosophers (thinkers of great
thoughts) have had a hard time with this question too. The problem is that
whatever you might say about something "living" you can probably imagine a
"machine" someday being able to do... if they can't already. There is a book
by a scientist called "I Robot" that Hollywood made into a movie (kind of...not
as good as the book) that imagines different robots that each have a certain
thing we think only we humans can have...like the ability to love, or cry or
lie...its an interesting book. What makes a living thing different from
non-living and what makes a human a human...keep on thinking about it! If
you figure it out e-mail me. I want to know.
This is one of my favorite questions. In fact, scientists don't
entirely agree on the answer. It is generally agreed that all living
things have a few features in common: they all respond to their
environments, they all grow and develop, they all use energy, they all
can reproduce, they all maintain a steady chemical balance inside
themselves (homeostasis), they are all composed of cells, and all
populations of organisms evolve over time.
There are a few examples of things that are difficult to classify as
living or non-living. Viruses, for example, have some features of
living things (reproduction, evolution, energy use) but they lack other
features (cells, homeostasis). Some people who study viruses do
consider them to be alive, but most do not.
Or take the example of a chicken egg that has just been laid. Let's say
there are no roosters around. Clearly, the egg will not develop into a
chick, and we should probably consider it to be non-living. But it is,
essentially, a cell from a living chicken and it clearly began as a
living cell and it still has all the biochemistry of a living cell. So
at what point did it "cross the line" from a living cell to a non-living
one? It's very difficult to come up with a completely satisfactory
You probably already know what living organisms are like.
All the world's animal, plants, and germs are living organisms.
They move around, eat some kind of food, grow bigger,
make new ones of their own kind,
and they do smart things to survive when the world around them changes a
Smarter than a rock, anyway.
In a year or two your school will probably teach you the
"rules" for being a living organism.
Most of them are listed in the paragraph above.
The world has a few in-between things
which we can't decide for sure whether to call them "living" or not.
Virus-germs multiply, but they never grow bigger.
they are either built to their full (very tiny) size,
or they aren't working viruses yet.
And they can't do it without "taking over" the guts of a bigger, fancier
Most scientists think of them as the smallest possible living organism.
Crystals (like sugar crystals) grow bigger, but they don't do anything
If you break one into pieces you have many new crystals to grow bigger.
But we don't think of crystals as being alive at all.
We think of them as rocks, which nature is accidentally building more of.
Personally, I think smart, complicated, goal-oriented behavior
is the real definition of life.
Living things "try" to do something. Usually they try to survive.
Hope that explains it for you...
A living organism is made up of cells. That is the only thing required in
order for you to be able to call it alive. Cells are to small to see. Every
part of our body is made of cells. Plants are made of cells. The difference
is some cells look different from other cells and they have different "jobs"
to do to keep the organism alive.
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Update: June 2012