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33 Cards in this Set
- Front
- Back
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weather
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an area's short term atmospheric conditions typically over hours or days
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examples of atmospheric conditions
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1. temperatures
2. pressure 3. moisture content 4. precipitation 5. sunshine 6. cloud cover 7. wind direction and speed |
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a ____ often brings cloudy skies and drizzle
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warm front
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the northern hemisphere is tilted toward the sun in ____ and away from it in
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June, December
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In the sub-polar regions, where summers are cool and short, the predominant vegetation is
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coniferous evergreen
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Deserts take a long time to recover from disturbance because of their...
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slow plant growth
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mountains are ecologically important because they...
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-reflect solar radiation back into space
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Arctic Tundra receive scarce ______
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rainfall
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Mountains make up ____% of the earth's land surface
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25%
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what is a front?
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the boundary between two air masses with different temperatures and densities
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what is a warm front?
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-Since warm fronts are less dense than cool air it rises over a mass of cool air
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cold front
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the leading edge of an advancing mass of cold air staying close to the ground under the warmer air
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what does a cold front produce?
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thunderheads: rapidly moving, towering clouds
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what happens after the cold front passes through?
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have cooler temperatures and a clear sky
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jet streams
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-near the top of the troposphere
-hurricane force winds -they follow rising and falling paths that have a strong influence on weather patterns |
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where is atmospheric pressure greatest?
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near the earth's surface because the molecules in the atmosphere are squeezed together under the weight of the air above
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high
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-an air mass with high pressure
-contains cool, dense air that descends toward the earth's surface and becomes warmer |
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what follows a high?
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fair weather follows as long as the high pressure air mass remains over an area
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low
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-a low pressure air mass
-produces cloudy and sometimes stormy weather - |
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dew point
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when the temperature drops below a certain level where condensation takes place moisture in the air condenses and forms clouds
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two extames of weather extremes
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1. tornadoes
2. tropical cyclones |
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tornadoes
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-form over land
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tropical cyclones
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form over warm ocean water and sometimes pass over coastal
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what is the world's most tornado prone country?
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US
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When do most tornadoes occur?
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into the spring when fronts of cold air from the north penetrate deeply into the midwestern plans
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climate
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a region's long term atmospheric conditions - typically over decades
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what are the two main factors determining a region's climate
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average temperature and average precipitation
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microevolution
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a small genetic change that can occur in a population
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macroevolution
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long term, large scale evolutionary changes through which new spices form from ancestral species and some species are lost through extinction
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what is the first step in evolution
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the development of genetic variability in a population
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alleles
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-a particular gene may have two or more different molecular form
-each individual of a population can have different combinations of alleles |
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mutations
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random changes in the structure or umber of DNA molecules in a cell that can be inherited by offspring
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how does mutations occur?
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1. by exposure of DNA to external agents such as radioactivity, X rays, and natural and human made chemicals
2. random mistakes in DNA coding |
