| Facts About Viruses That Will Shock
You
Most people consider viruses as living things the can reproduce
on their own to spread and infect their hosts. The fact is, viruses
are neither alive nor can they reproduce like other living organisms.
Anyone with a cold or the flu virus feels as if they are under
attack by some organism. However, a virus does not belong to the
kingdom of living things. Just because a virus seems alive doesn't
mean it is alive. After all, it's not even a single-cell organism.
A virus is little more than a strand of DNA or RNA covered by
a protein coating. Viruses are a thousand times smaller than bacteria
and come in a wide range of shapes. Some look like weird, tall
spiders whereas others look like prickly porcupine-like soccer
balls.
One thing is for sure; viruses are very much a part of life on
Earth and the human experience. Viruses infect animals, plants,
and even bacteria. There are millions of different types of viruses
found in almost every ecosystem on Earth and these minute structures
are the most abundant type of biological entity. When considering
that not only is viral presence on this planet all encompassing,
but every sequenced organism to date has a major component of
its genome that is viral in origin, it becomes apparent that viruses
are integral players in the evolution of what we presently consider
life.
Humans are in a constant battle with viruses. HIV (the virus that
causes AIDS), the Ebola virus, and the West Nile virus continue
to make headlines and take millions of lives. Recently, the H1N1
strain has made headlines as a pandemic virus as declared by the
World Health Organization.
The probably multiple origins of viruses are lost in a sea of
conjecture and speculation, which results mostly from their nature:
no-one has ever detected a fossil virus as a particle; they are
too small and probably too fragile to have withstood the kinds
of processes that led to fossilisation, or even to preservation
of short stretches of nucleic acid sequences in leaf tissues or
insects in amber.
Are Viruses Alive?
Even though there is no precise definition of what separates the
living from the non-living, there are a few common characteristics
which many biologists consider requirements of life. Some nonliving
things may have one or more of the characteristics but not all
of them. For a virus then to be classified as alive it must:
*
Reproduce
*
Obtain and use energy
*
Grow, develop, and die
*
Respond to the environment
Viruses Cannot Use Their Genetic Material By Themselves
Viruses do have DNA or RNA, and DNA is the code for life. Having
genetic material is an important step towards being classified
as alive. DNA controls the evolution of the cell and the organism.
Like living things, viruses evolve through time and thus can adapt
to their environment. But unlike cells, viruses cannot use their
genetic material by themselves. Living matter reproduces and passes
on genetic material as a blueprint for growth and subsequent reproduction.
However, viruses need a living cell in order to function and reproduce;
otherwise they are playing dead.
Viruses Cannot Divide or Reproduce Themselves Without a Host
Cell
Because viruses are not cells, they can't divide by binary fission
like bacteria. Yet they do reproduce themselves in an extraordinary
way. Their structure enables viruses to attack a plant or animal
cell called a host cell. The protein shell protecting the virus'
DNA is covered with spikelike protrusions. These spikes allow
the virus to latch onto the cells they infect. Once hooked on,
the virus injects its genetic material into the host cell.
The virus' DNA takes control of the cell once it's within the
cytoplasm and begins to make the cell produce virus DNA and other
parts of viruses. The host cell is forced to expend all of its
energy and resources to help the virus replicate and make hundreds
more viruses. The poor, weak cell usually bursts like an overinflated
balloon from all the viruses and is destroyed in the process.
Then, the replicated virus attaches itself to a new, unaffected
host cell, and the viral infection continues.
Viruses Do Not Produce or Utilize Their Own Energy
Living things do more than just reproduce. They also must obtain
food to fuel the cell's metabolic activity. Some organisms, such
as animals, eat other living things for energy. Other organisms,
such as plants, harness the Sun's energy to make their own food.
Because viruses aren't cells and have no activity within it, it
has no need for food. However, the virus-controlled host cell
needs material and energy to reproduce the viruses.
Viruses Do Not Grow
All other living things also grow or get bigger. A virus does
nothing inside its protein coat; therefore it does not grow.
Viruses Cannot Move Themselves
Plants and animals react to the environment. All living things
have ways of sensing the world around them and can respond to
changes in their environment. Homeostasis is the property of an
open system, especially living organisms, to regulate its internal
environment so as to maintain a stable condition. Do viruses react?
Viruses cannot move themselves, viruses can react to some changes
in their environment but they have a very minimalistic internal
environment.
Remember, the virus' DNA or RNA can evolve over time, thereby
increasing its chances for survival and adapting to the environment.
Like bacteria, they adapt through genetic mutations caused by
rapid reproduction. That is why it is so hard to cure viral diseases.
Viruses keep changing their DNA and protein coat to further their
"life form" and keep ahead of the game.
Therefore, since a virus does not meet most of the requirements
considered to be a living thing, a virus is not alive.
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