Name: _____________________________________ Virus Active
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Introduction
Scientists estimate that there are roughly 1031 viruses at any given moment^11start
superscript, 1, end superscript. That’s a one with 31 zeroes after it! If you were somehow
able to wrangle up all 1031 of these viruses and line them end-to-end, your virus column
would extend nearly 200 light years into space. To put it another way, there are over ten
million times more viruses on Earth than there are stars in the entire universe
Does that mean there are 1031 viruses just waiting to infect us? Actually, most of these
viruses are found in oceans, where they attack bacteria and other microbes. It may seem
odd that bacteria can get a virus, but scientists think that every kind of living organism is
probably host to at least one virus!
What is a Virus?
A virus is a tiny, infectious particle that can reproduce only by infecting a host cell. Viruses
"commandeer" the host cell and use its resources to make more viruses, basically
reprogramming it to become a virus factory. Because they can't reproduce by themselves
(without a host), viruses are not considered living. Nor do viruses have cells: they're very
small, much smaller than the cells of living things, and are basically just packages of nucleic
acid and protein.
Still, viruses have some important features in common with cell-based life. For instance,
they have nucleic acid genomes based on the same genetic code that's used in your cells
(and the cells of all living creatures). Also, like cell-based life, viruses have genetic variation
and can evolve. So, even though they don't meet the definition of life, viruses seem to be in
a "questionable" zone. (Maybe viruses are actually undead, like zombies or vampires!)
1. A virus can only reproduce by ________________________ a cell.
2. Are viruses living or nonliving?
3. Are viruses larger or smaller then cells?
4. All viruses have nucleic acid __________________ based on the same genetic code used
in your cells.
How are viruses different from bacteria?
Even though they can both make us sick, bacteria and viruses are very different at the
biological level. Bacteria are small and single-celled, but they are living organisms that do
not depend on a host cell to reproduce. Because of these differences, bacterial and viral
infections are treated very differently. For instance, antibiotics are only helpful against
bacteria, not viruses.
Bacteria are also much bigger than viruses. The diameter of a typical virus is
about 20 - 30 nanometers. This is considerably smaller than a typical E. coli bacterium,
which has a diameter of roughly 1000 nanometers! Tens of millions of viruses could fit on
the head of a pin.
5. Are viruses and bacteria the same or different?
