Lecture 15: The Biosphere PDF

Lecture 15: The Biosphere  Today Introduction to ecology Factors influencing climate The biosphere: the zone of life on Earth – Terrestrial biomes – Freshwater ecosystems – Marine ecosystems  What is Ecology? Scientific study of interactio...

Lecture 15: The Biosphere  Today Introduction to ecology Factors influencing climate The biosphere: the zone of life on Earth – Terrestrial biomes – Freshwater ecosystems – Marine ecosystems  What is Ecology? Scientific study of interactions between organisms and their environments  What is Ecology? Interactions with: – Physical aspects of environment (abiotic factors)  Identify some abiotic factors  What is Ecology? Interactions with: – Other organisms (biotic factors)  Identify some biotic factors  What is Ecology? Levels of ecological study: organism population community ecosystem  Define each term. What is Ecology?  The Biosphere Biome – large-scale ecosystem – Categorized by dominant vegetation type – Has characteristic climate  Factors Influencing Climate Many factors affect a region’s climate – Solar radiation – Atmospheric circulation – Ocean currents – Regional geography – Seasonal variation Climate determines the types of species present  Factors Influencing Climate Unequal heating of the Earth’s surface by the sun  Factors Influencing Climate Unequal heating drives atmospheric circulation  Factors Influencing Climate 4 Cool, dry air Air warms, picks up descends. Air moisture, ascends, cools 3 circulation and gives up moisture. patterns: Cooled, drier air 2 descends at 30° N and S. At the equator, air 1 is warm and wet. The air rises, then cools and gives up moisture. 2 3 4  Factors Influencing Climate Unequal heating by solar radiation Atmospheric circulation Earth’s major climate zones  Factors Influencing Climate Air circulation, Earth’s rotation, and land masses drive oceanic circulation  Factors Influencing Climate Rain shadow – dry region on the side of a mountain facing away from the wind  Factors Influencing Climate Rain shadow 3. Air 4. Air descends releases and warms 2. Air rises moisture and cools 1. Air picks up 5. Hot, dry air evaporated creates a desert moisture WIND DIRECTION Lush, productive communities Sparse, drought-resistant communities  Factors Influencing Climate Rain shadow Sierra Nevada rain shadow  Factors Influencing Climate  How do coastal areas differ from inland areas? Why? Annual temperature variation  Terrestrial Biomes  Why do we use the dominant vegetation type to characterize biomes? 1 6 2 7 3 8 Label the 4 Mountain zones biomes 5 Polar ice  Tropical Rainforest 0° – 20°N and S High precipitation, little seasonal changes High biomass, high diversity Tall, broadleaved trees  Savanna North and south of wet tropics Wet and dry seasons Shorter trees More grasses/shrubs  Savanna Balance of trees vs. grasses affected by rainfall, fire, grazing, and flooding  Desert 30°N and S High temperatures, low moisture Low plant abundance, but high diversity Succulent or woody plants CHAPARRAL  Chaparral 30° to 40°N and S Mediterranean climates – cool, moist winters and warm, dry summers Evergreen shrubs Frequent fires Nutrient-poor soil  Chaparral 30° to 40°N and S Mediterranean climates Small, tough leaves Evergreen shrubs prevent water loss Frequent fires Nutrient-poor soil  Temperate Grassland 30° to 50°N and S Warm, moist summers and cold, dry winters Grasses dominate Frequent fires Fertile soil  Temperate Deciduous Forest Majority 35° to 50°N Moderate climate, long growing season Deciduous leaves Fertile soil  Boreal Forest (Taiga) 50° to 65°N Continuous cold, wet conditions Coniferous trees Frequent fires Poor soil quality  Tundra Above 60°N Cold temperatures, low precipitation Low-growing vegetation Widespread permafrost Slow decomposition  Human Impacts Humans affect the actual distribution of biomes – Population size, land development, and resource use  Which biomes have been most affected?  Human Impacts Deforestation – Logging (wood and paper) – Conversion to cropland or pasture 1975 1992 Rondônia, French Guiana Brazil 1986 2001  Human Impacts Desertification – Conversion of grassland or woodland to desert – Caused by unsustainable grazing practices  Aquatic Ecosystems Photic zone has enough light for photosynthesis – 0-200 m – Contains majority of aquatic life  Freshwater Ecosystems Still waters – lakes and ponds – Depth and area determine community  Freshwater Ecosystems Moving waters – streams and rivers – Water velocity, temperature, depth, and chemistry determine community  Marine Ecosystems Categorized by location relative to shorelines and ocean bottom  Marine Ecosystems Estuaries – where rivers flow into the ocean – Variable salinity – Input of sediment and nutrients – High productivity – Safe from marine predators  Marine Ecosystems Rocky intertidal – Organisms attached to substrate – Harsh, highly variable conditions – Community arranged according to tolerance  Marine Ecosystems Coral reefs – shallow tropical water – Corals host photosynthetic algae – Complex habitat – High diversity – High productivity  Marine Ecosystems Kelp forests – coastal temperate water – Tall stands of algae (kelp) – Anchored to substrate – High productivity  Marine Ecosystems Pelagic zone – open ocean beyond continental shelf – Photic zone supplies most of the energy – Swimming organisms, plankton, and seabirds  Marine Ecosystems Pelagic zone – open ocean beyond continental shelf  Marine Ecosystems Benthic zone – ocean floor – Shallow areas often diverse – Deep areas are sparsely populated – Organic matter in sediments  Human Impact on the Oceans Effects from greenhouse gases, pollutants, overfishing – Severity varies – Poorly understood overall  Study Questions What are abiotic and biotic factors? Give some examples. List and explain the different levels of ecological organization. How does the intensity of solar radiation differ across the surface of the planet, and how does this affect climate? What are atmospheric circulation cells? Why do they occur? Describe specifically where air moves, how much moisture and heat the air contains, and how this relates to climate zones. What is a rain shadow? Where do they occur, and what is the result? What are biomes? How do we define biomes, and why? Describe the characteristics of each of the biomes we discussed, including rainfall, temperature, seasonal variation, and fire. What are some typical plant features or types in each biome, and why? Describe the different aquatic ecosystems that we discussed.