Page 34 - 新思维科学学生用书6 样章
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1.4 Diseases
Living things that cause disease
Diseases stop our bodies from working properly. There are
different kinds of living things that cause diseases. They infect
other living things and grow and reproduce on or in the body of
the living thing that they infect. Any living thing that lives on or
in the body of another living thing is called a parasite. The living
thing that a parasite infects is called the host.
Bacteria are very small living things that we
can only see using a microscope. Bacteria
cause diseases such as cholera and pneumonia.
Not all bacteria are harmful.
Viruses are even smaller than bacteria.
Almost all viruses are harmful and cause diseases
in humans, other animals and plants. Some
viruses even infect bacteria! Humans get flu,
chicken pox and measles from viruses.
The yeast that we use to make bread rise is
a fungus. Mushrooms that we eat are also
fungi. But some fungi are parasites that cause
diseases. Ringworm in humans and other animals,
athlete’s foot in humans and rusts in plants are caused by fungi.
There are other kinds of parasites that cause infectious
diseases. Malaria and dysentery are two diseases caused by
these parasites.
Questions
1 a What is a parasite?
b Why are viruses, some bacteria and fungi parasites?
2 Make a table of the different kinds of living things that cause diseases and name
two examples of a disease that each one causes.
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