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Paleozoic era

(Encyclopedia)Paleozoic era pāˌlēəzōˈĭk [key], a major division (era) of geologic time (see Geologic Timescale, tablegeologic timescale, table) occurring between 570 to 240 million years ago. It is subdivide...

pollen

(Encyclopedia)pollen, minute grains, usually yellow in color but occasionally white, brown, red, or purple, borne in the anther sac at the tip of the slender filament of the stamen of a flowering plant or in the ma...

ozone layer

(Encyclopedia)ozone layer or ozonosphere, region of the stratosphere containing relatively high concentrations of ozone, located at altitudes of 12–30 mi (19–48 km) above the earth's surface. Ozone in the ozone...

Venus, in astronomy

(Encyclopedia)Venus, in astronomy, 2d planet from the sun; it is often called the evening star or morning star and is brighter than any object in the sky except the sun and the moon. Because its orbit lies between ...

water

(Encyclopedia)CE5 A. Water molecule (black circles represent valence-shell electrons) B. Structure of ice: Each oxygen atom (white circles) is bonded to four other oxygen atoms by hydrogen bonds, the hydrogen at...

space probe

(Encyclopedia)space probe, space vehicle carrying sophisticated instrumentation but no crew, designed to explore various aspects of the solar system (see space exploration). Unlike an artificial satellite, which is...

Embargo Act of 1807

(Encyclopedia)Embargo Act of 1807, passed Dec. 22, 1807, by the U.S. Congress in answer to the British orders in council restricting neutral shipping and to Napoleon's restrictive Continental System. The U.S. merch...

multiple birth

(Encyclopedia)multiple birth, bringing forth of more than one offspring at birth. Although many smaller mammals bear several young at a time, multiple births are relatively uncommon in humans and other primates. Tw...

stem

(Encyclopedia)stem, supporting structure of a plant, serving also to conduct and to store food materials. The stems of herbaceous and of woody plants differ: those of herbaceous plants are usually green and pliant ...

Ute

(Encyclopedia)Ute yo͞ot, yo͞oˈtē [key], Native North Americans whose language belongs to the Shoshonean group of the Uto-Aztecan branch of the Aztec-Tanoan linguistic stock (see Native American languages). In t...