THE BIOSPHERE

The biosphere is the sum total of all places in which organisms live

I. Climate

A. Weather - the condition of the atmosphere at any given time

B. Climate - the accumulation of weather events over a long period of time (temperatures, humidity, wind, cloud cover, rainfall)

C. Climate is dependent upon several factors:

1. Solar radiation (see below)

2. The earth's daily rotation - determines day length

3. The earth's rotation around the sun - determines seasons

4. The distributions of continents and oceans - recall that water resists temperatures changes, therefore large bodies f water moderate temperatures

5. Elevation - affects both temperature and humidity

II. Solar radiation

A. Heat energy from the sun drives the earth's weather systems, which ultimately determine the composition of ecosystems

B. Only about half the solar radiation entering the upper atmosphere makes it through to the earth's surface. The ozone layer is responsible for most of this filtering affect

C. There are different climates on earth because the earth heats unevenly. This is because the earth is tilted 23°27' on its axis. Therefore the intensity of solar radiation per unit area is always less at high latitudes than at the equator. Equatorial regions receive about five times more energy than polar areas

D. The tilting of the earth on its axis also means that at the equator the days and nights are each 12 hours long, whereas at the poles there are six month long light and dark periods. Therefore low latitudes are warmer than the poles. This unequal distribution of heat causes a mass transfer of heat from the equator to the poles both by air and water movements. It is responsible for the wind and ocean patterns on earth

III. Global air and ocean circulation patterns

A. Energy from the sun is more concentrated at the equator

B. Warm equatorial air rises and spreads towards the cooler poles

C. The non equal distribution of land masses creates variations in air pressure. Recall that water resists temperature changes. Therefore land surfaces heat up faster and cool faster than the ocean surfaces. Air pressure decreases where air rises (and increases where air sinks). These differences give rise to winds that disrupt the movement of air from the equator to the poles

C. The spinning of the earth results in the deflection of moving air masses, this is called the Coriolis effect or force. The Coriolis effect deflects moving air or water to the right in the northern hemisphere and to the left in the southern hemisphere

D. Ocean currents are affected by the same factors as air currents. They are just slower due to the density of water

IV. Topography

A. Topography, the physical features of a region, also greatly affect its climate

B. Rain shadows, such as the one created by the Sierra Nevada Mountains, are created by topographic differences

1. As air blows up over a mountain, it rises and cools; windward side of the mountain receives more rainfall

2. The leeward side of the mountain range receives dry air; forming a rain shadow

V. Soils

VI. Biomes

A. The global circulation patterns of the atmosphere and oceans, coupled with differences in topography give rise to regional differences in temperature and precipitation

B. Temperature and precipitation are the major environmental parameters which determine the nature of ecosystems

C. Biome - a characteristic mix of plants and animals adapted to living under certain environmental conditions

D. The distribution and key features of biomes are the outcome of temperatures, soils and moisture levels (which vary with latitude and altitude), and evolutionary history