Page 252 - New Medley 4 Semester 1

and even in air. Some microbes are friendly and are good to us, while some

others are very harmful to us.

TYPES OF MICROBES

Microbes are grouped into four types: Bacteria, viruses, protozoa and fungi.

Bacteria

Bacteria (sing. bacterium) are found everywhere. They are present on and inside
our body. Bacteria are so tiny that thousands of them can fit on the tip of a

needle. Most bacteria cannot make their food. They get their food both from
living organisms and rotting or decaying matter.

Bacteria are of different shapes. They can be round or oval, rod-shaped, spiral
or comma-shaped.

Round Bacteria Rod-shaped Spiral Bacteria Comma-shaped
Bacteria Bacteria
Bacteria of different shapes

Viruses

Viruses are smaller than bacteria. They cannot be seen even through a simple
microscope. Scientists find it difficult to classify them as living or non-living

things because they stay dead and do not reproduce outside the body of living
organisms. They act as living being and reproduce only when they get into the
body of living organisms.

Viruses are always harmful to us. They are never friendly. They cause diseases in

plants as well as in animals and human beings.

Protozoa

Protozoa are bigger than bacteria in size. Their body

is made up of one cell only. Therefore, they are called
single-celled organisms. They can move from place to

place. So, they are classified as animals. Amoeba and Paramecium Amoeba
Paramecium are common protozoa. Some protozoa Some protozoa

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