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Sicentists classify organisms based on their similarities and differences. Old
classification systems were based only on characteristics that could be
observed with the eye, sometimes aided by a microscope. Size, shape, color,
body structure, and method of food-getting are examples of such
characteristics.
For many years, scientists classified all organisms as either plants or
amimals. Today, scientists are able to study the molecules that make up
organisms. For this reoson, classification systems may change as similarities
and differences in molecules are discovered. One accepted classification is
the division of organisms into five main groups, called kingdoms. The five
kingdoms are the animal kingdom, the plant kingdom, the fungus kingdom,
the protist kingdom, and the moneran kingdom.
Most organisms in the animal kingdom can move about. Some animals fly,
some swim, and others walk on the ground. Also, animals cannot make their
own food. They eat other organisms for food.
Plants have characteristics diffenrent from animals and organisms in other
kingdom. Plants usually have a green substance called chlorophyll. They use
chlorophyll to make food. Also, a plant usually spends its whole life in one
place.
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