Micro life
It can make 4,000 million million million copies.
153
Vaccinations
Vaccinations can help to
protect people from harmful
diseases. A person is injected
with a weakened form of a
virus or bacterium. This helps
the immune system defend
itself against the real thing.
Viruses
Viruses are many times smaller than
bacteria. They are shaped like spheres
or rods. Viruses are not really alive,
because they are not made of cells.
They only become active when they
invade a cell. They copy themselves
by taking over the cell and turning it
into a virus factory.
Plant viruses
Plant viruses can change the way
that plants develop. For example,
one virus affects the pigment in
tulips’ petals. It stops the pigment
from working in
some places. This
makes the petals
look stripey.
Protists
Protists are another
kind of single-celled
life form. They are
very varied. Some
protists are similar
to fungi, animals, or
plants. Some protists
group together into
colonies.
Harmful viruses
Viruses can cause
different illnesses.
Rabies
is a fatal virus
that is common in animals
such as dogs.
Chickenpox
is easy to
catch. The main symptom
is spots that itch.
Colds
are viruses and can
bring on a sore throat,
runny nose, and cough.
DNA or
RNA strand
The streaked patterns
on this tulip are caused
by a virus.
A virus has made
light patches
appear on
these leaves.
Protective
protein coat
Model of a virus
