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There are at least 400,000 known species of plants in the world. Vast numbers of plants have existed in earlier geological eras, a great number of which are now extinct. Of the plants that exist today, most belong to a group of “higher plants” that have roots, stems, and leaves, and that produce seeds in order to reproduce. Plants range in size from a single cell to giant sequoia trees, which can grow up to 240 feet (80 meters) tall.

Biologists have classified all living organisms into two kingdoms—the animal kingdom and the plant (Plantae) kingdom. Plants are distinguished from animals because most animals can achieve locomotion at will, while plants are rooted and cannot move to a new location unless carried by water or wind. ...

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