Download Are Viruses Living? - Hartland High School

Virus
A virus is a microscopic particle that can infect the cells of a biological organism.
Viruses can only replicate themselves by infecting a host cell and therefore cannot
reproduce on their own.
At the most basic level, viruses consist of genetic material contained within a protective
protein coat called a capsid; the existence of both genetic material and protein
distinguishes them from other virus-like particles such as prions and viroids.
They infect a wide variety of organisms: both eukaryotes (animals, fungi and plants) and
prokaryotes (bacteria).
A virus that infects bacteria is known as a bacteriophage, often shortened to phage.
The study of viruses is known as virology, and those who study viruses are known as
virologists. It has been argued extensively whether viruses are living organisms.
Most virologists consider them non-living, as they do not meet all the criteria of the
generally accepted definition of life.
They are similar to obligate intracellular parasites as they lack the means for selfreproduction outside a host cell, but unlike parasites, viruses are generally not
considered to be true living organisms.
A primary reason is that viruses do not possess a cell membrane or metabolise on their
own - characteristics of all living organisms.
Examples of common human diseases caused by viruses include the common cold, the flu,
chickenpox and cold sores.
Serious diseases such as Ebola, AIDS, bird flu and SARS are all also caused by viruses.
Are Viruses Living?
9 June 2004
Let’s first define life. According to the online Merriam-Webster Dictionary, life is “an
organismic state characterized by capacity for metabolism, growth, reaction to stimuli,
and reproduction.”
Viruses are not living things. Viruses are complicated assemblies of molecules, including
proteins, nucleic acids, lipids, and carbohydrates, but on their own they can do nothing
until they enter a living cell. Without cells, viruses would not be able to multiply.
Therefore, viruses are not living things.
When a virus encounters a cell, a series of chemical reactions occur that lead to the
production of new viruses. These steps are completely passive, that is, they are
predefined by the nature of the molecules that comprise the virus particle. Viruses don’t
actually ‘do’ anything. Often scientists and non-scientists alike ascribe actions to viruses
such as employing, displaying, destroying, evading, exploiting, and so on. These terms
are incorrect because viruses are passive, completely at the mercy of their environment.