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Biomes
- Major vegetation zones of the Earth with characteristic vegetation and animals
- Characteristic life forms in each biome with similar body plan but not related taxonomically
- Convergent evolution occurs in biomes (e.g. cactus-like plans in deserts; cacti in North America, euphorbs in Africa)
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Major Biome Types
- Tundra
- Taiga (northern coniferous forest)
- Grasslands
- Temperate forests
- Tropical forests
- Desert
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Biome type is determined by the interactions of
- Climate - overriding cause
- Geography - can modify climate
- Soils - related to geography, geology, and climate
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Climate
average weather over the course of several years
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Major factors of climate are affected by
- latitude
- positions of continents
- geophysical features such as mountains and plains
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Causes of Climate
- Directness of Insolation
- Tilt of Earth at 23° on Axis
- Prevailing Winds
- Ocean currents
- Geography
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Directness of Insolation (Climate)
- how direct incoming sunlight is at a point on Earth
- due to the fact that Earth is a sphere
- Equatorial regions - more direct, warmer
- Polar regions - more indirect, cooler
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Tilt of Earth at 23 degrees on axis
- Causes seasonality
- Less seasonality at equator - effect of tilt less pronounced
- More seasonality toward poles - effect of tilt more pronounced
- Northern Hemisphere tilts toward the sun in summer - insolation more direct
- Northern Hemisphere tilts away from the sun in winter - insolation less direct
- Southern Hemisphere - vice versa
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Prevailing Winds
- Due to uneven heating of Earth's surface and rotation of Earth
- Descending air = adiabatic warming, less rainfall
- Rising air = adiabatic cooling, more rainfall
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Global Atmospheric Circulation Patterns
- North pole to 60° N - Descending
- 60°N to 30°N - Rising
- 30°N to Equator - Descending
- Equator to 30°S - Rising
- 30°S to 60°S - Rising
- 60°S to South Pole - Descending
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Why are most deserts at 30° North or South and tropical rainforests are near or at the equator?
- Warm air rises in equatorial regions, which absorbs water readily
- Adiabatic cooling of the air mass occurs as it rises; cooler air holds less water, causing rain in the tropics
- Rain results in dry air as the air mass descends at 30° North or South
- Furthermore, adiabatic warming of the air mass warms the air and holds more water
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Ocean Currents
- Water retains heat well
- circulates in huge circular gyres
- carry heat from equator to poles
- can moderate climate near costs
- east coasts - warmer (equator to pole)
- west coasts - cooler (pole to equator)
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Continental Climates
- away from moderation by oceans
- have colder winters
- e.g. Siberia and Alberta are on the same latitude as London but have much colder winters
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How do mountains affect climate?
- Localized climates due to great differences elevations over short distances
- Can affect rainfall
- Rain occurs on windward side of the mountain
- Moist air is forced upward, with the adiabatic cooling causing rain
- Air descends on leeward side of mountain
- Adiabatic warming occurs, creating a dry climate - effect known as rain shadow
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