Microscopic Life
There is a world all around you that
you cannot see. Billions of tiny creatures slither and slide over tables and
floors. They float and wiggle in drops of water. They stick to your skin.
Sometimes they get in your eyes, nose, and throat.
You can see most of these tiny
things only if you put them under a microscope. These tiny life forms are called
microscopic life or microorganisms. They are also called microbes. Most microbes
are made of just one cell. Your body, by contrast, has billions of cells.
MANY KINDS OF MICROBES
There are thousands of different
kinds of microbes. Microbes called bacteria are the smallest living things.
Bacteria live almost everywhere: on land, in water, and even inside you.
Some microscopic life forms are
like plants. Tiny diatoms are microbes that live in lakes and the ocean. Diatoms
soak up sunlight and use its energy to make food, just like plants.
Some microscopic life forms are
more like animals. Protozoa such as the amoeba and paramecium are animal-like
microorganisms. An amoeba can move by changing the shape of its body. It sticks
out a pseudopod, or false foot. A paramecium is covered with tiny hairs. It
waves its hairs rapidly to swim.
Viruses are another kind of
microbe. Viruses sometimes act like living things and other times act like
nonliving things. Viruses sometimes live in the cells of plants and animals.
Inside a cell, a virus reproduces like a living thing. The virus uses the cell
to make many copies of itself. Viruses are too small to see with an ordinary
microscope. You need a powerful electron microscope to see a virus. Outside of a
plant or animal cell, a virus is like a nonliving thing.
ARE MICROBES HARMFUL?
Some microbes are harmful. Some
microbes are helpful. Protozoa called plasmodium cause a serious disease called
malaria. Some bacteria and viruses can make you sick. We sometimes call these
microbes germs.
Harmful bacteria can make food
spoil. You can get sick to your stomach if you eat the food. Some harmful
bacteria can cause an infection in a cut or sore. Others cause pneumonia, strep
throat, tuberculosis, typhoid fever, and other diseases.
Viruses cause chicken pox,
measles, flu, and common colds. They also cause very serious diseases such as
rabies, polio, and acquired immunodeficiency syndrome (AIDS).
WHAT DO HELPFUL MICROBES DO?
Harmless bacteria in your body
compete with harmful germs. Harmless bacteria compete for food and keep the
harmful germs under control. Some bacteria in your body help you digest your
food.
Some bacteria in the soil help
plants grow. The bacteria break down dead plants and animals into chemicals that
plants can use. Some bacteria take nitrogen gas out of air and water. They
change the nitrogen so that plants can use it to help make food.
Diatoms are important food for
fish. Diatoms are part of the plankton that floats on the ocean. Plankton is
made up mostly of microscopic life forms. Many kinds of animals that live in the
ocean eat plankton.
WHO DISCOVERED MICROORGANISMS?
A Dutch scientist named Antoni van
Leeuwenhoek was the first person to see microorganisms. He invented a microscope
more powerful than any that had previously been made. He saw microbes under his
microscope in 1676. He called the microscopic organisms “animalcules.”
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Science
