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Biogeography: Climate, Biomes, and Terrestrial Biodiversity WEATHER Short term tropospheric properties such as: • Temperature CLIMATE • Pressure • Cloud cover • Humidity • Precipitation • Wind direction and speed The average long-term weather of an area. Averaged over at least 30 years. Determined by two main factors: average temperature and average precipitation. Masses of air are constantly moving Weather front—the boundary between two different air masses. Warm front—warm air mass moves up and over of cold air mass. Cold front—cold air mass wedges beneath a warm air mass. The most dramatic changes in weather occur along a front. Tornadoes—form over land when cool downdrafts and warm updrafts meet during a thunderstorm. Tornado season in the United States is usually March through August. Tropical cyclones—form over warm ocean waters. • Hurricanes—in the Atlantic • Typhoons—in the Pacific NEGATIVE EFFECTS: Kill and injure people, property, and agriculture production. POSITIVE EFFECTS: Flush excess nutrients from land runoff Carve channels through barrier islands allowing huge quantities of fresh seawater to flood bays and marshes which can increase production of commercially important species of shellfish and fish. 1. 2. Uneven heating of the Earth’s surface Seasonal changes occur because the Earth’s axis is tilted. Fig. 6-8 p. 116 3. The Earth rotates on its axis. *Causes the Coriolos Effect 4. Long term variations in the amount of solar energy striking the Earth. *Milankovitch Cycles--Earth’s wobble (22,000 yrs.), tilt (44,000 yrs.) and changes in the shape of the Earth’s orbit (100,000 year cycle) Redistribute heat received form the sun and influence climate and vegetation especially near coastal areas. For example: • The Gulf Stream brings warm water up from the tropics. • Upwellings • El Nino-Southern Oscillation • La Nina Wind blowing along steep western coasts of continents push surface water away from land. This water is replaced by cold, nutrientrich bottom waters called upwellings. Nutrients from upwellings support large populations of phytoplankton, zoophankton, fish and fish-eating birds. During an El Nino, the prevailing westerly winds weaken or cease. This causes upwellings to cease. • Surface water along North and South America becomes warmer. • Nutrients are not brought to the surface causing a sharp decline in the numbers of some fish species. • Can trigger extreme weather changes over most of the globe, especially the Pacific and Indian Oceans. Fig. 6-14 p. 119 Sometimes El Nino is followed by La Nina. Westerly winds are stronger than normal resulting in more upwellings. Also results in extreme weather changes over most of the globe. • Colder waters in the pacific • More Atlantic hurricanes El Niño and La Niña.mht Gasses in the atmosphere, known as greenhouse gasses, trap long wavelength radiation (infrared) from the sun warming the air. Greenhouse Gasses: • Water vapor • Carbon dioxide • Methane Without the natural greenhouse effect, the Earth would be a cold, mostly lifeless planet. Various topographic features create local climatic conditions, or microclimates, that differ from the general climate of a region. Examples: • Mountains: Rain shadow Effect • Vegetation: take up and release water • Cities: bricks, concrete absorb heat Terrestrial regions of the Earth characterized by communities of organisms adapted to the climate. Annual precipitation, temperature, and soil are the most important abiotic factors that influence the location of biomes. Aquatic Ecology: Biodiversity in Aquatic Systems MARINE (SALTWATER) Estuaries Coastlines Coral reefs Coastal marshes Mangrove swamps Oceans FRESHWATER Lakes and ponds Streams and rivers Phytoplankton– plant plankton— microscopic photosynthesis organisms. Zooplankton—animal plankton– nonphotosynthetic primary and secondary consumers range from singlecelled to large invertebrates. Nekton—strong swimming consumers such as fish, turtle, and whales. Benthos—bottom dwellers Decomposers—mostly bacteria Less pronounced and fixed physical boundaries than terrestrial ecosystems. More complex and longer food chains and food webs More difficult to monitor due to their size and because they are largely hidden from view. In addition to salinity levels, the most important abiotic factors in aquatic life zone are: 1. Sunlight for photosynthesis. Photosynthesis is confined mostly to the upper laver, or euphotic zone. 2. Temperature 3. Dissolved oxygen (DO)—most fist die when the dissolved oxygen levels fall below 5 ppm. • Factors influencing DO levels include: Temperature Number of producers (add oxygen) Number of consumers and aerobic decomposers (remove O2) 4. Availability of nutrients Estuaries—An ecotone between the marine environment and the land where large volumes of fresh water from land and salty ocean water mix. Intertidal Zone—the area between high tide and low tide; changing moisture and salinity levels, numerous ecological niches. Coral reefs—form in clear, warm coastal waters of the tropics and subtropics. • Among the world’s oldest, most diverse, and productive ecosystems. • Home for about one-fourth of all marine species. • Often called the (Rainforest of the Sea) • Vulnerable to damage because they: Grow slowly Are disrupted easily Corals can live only in water temps. of 18-30 deg. C. (64-86 F) Standing water—lakes and ponds Flowing water—streams and rivers Classified according their nutrient levels. Oligotrophic—young, deep lake with low nutrient levels and limited food. Eutrophic—old, more shallow lake with high nutrient levels and complex feeding relationships. Mesotrophic –fall between the two extremes. Fig. 7-21 p. 158 Fig. 7-21 p. 158 Cultural eutrophication—occurs when human activities speed the eutrophication processes. Nutrients in runoff are carried into a lake causing a rapid increase in algae growth that then die and decay. Aerobic bacteria causing the decay of the plants, remove large amounts of oxygen causing the death of many other species.