Ecosystems and the Physical Environment

1. Ecosystems and the Physical Environment 4

2. Overview of Chapter 4 • Cycling of Materials within Ecosystems • Solar Radiation • The Atmosphere • The Global Ocean • Weather and Climate • Internal Planetary Processes

3. Cycling of Materials • Matter moves between ecosystems, environments, and organisms • Biogeochemical cycling involves • Biological, geologic and chemical interactions • Five major cycles: • Carbon, Nitrogen, Phosphorus, Sulfur and Water (hydrologic)

4. The Carbon Cycle

5. Carbon Cycle 6 processes that drive the carbon cycle: photosynthesis, respiration, exchange, sedimentation, and burial, extraction and combustion. • Producers convert carbon dioxide into sugars. • 2 Sugars are convert back into carbon dioxide. • Some carbon can be buried • Human extraction of fossil fuel bring carbon to Earth’s surface, where it can be combusted. • Carbon dixoide in the atmosphere and carbon dioxide dissolved in water are constantly exchanged.. • Combustion converts fossil fuel and plant material into carbon dioxide.

6. Human Activities and the Carbon Cycle • Since the Industrial Revolution human activities have had a major influence on the carbon cycle. • Combustion of fossil fuels where fossilized carbon is release into the atmosphere which increase retention of heat energy. (global warming) • Tree harvesting: destruction of forest increase carbon dioxide

7. The Nitrogen Cycle

8. Nitrogen cycle • Organisms need nitrogen. • A lack of nitrogen constrains the growth of the organism. (ex: adding other nutrients like water and/or phosphorus will not improve plant growth in a nitrogen poor soil.)

9. Nitrogen Cycle • 1 Nitrogen Fixation-Converts nitrogen from the atmosphere. Biotic processes convert nitrogen to ammonia where as abiotic processes convert nitrogen into nitrate. ex: Biotic cyanobacteria that live in the roots of legumes.) ex: Abiotic : lightning forms fires and burning fossils fuels. This is then carried by precipitation.

10. Continue: Nitrogen Cycle • 2. Assimilation: Producers take up either ammonium or nitrate. Consumers get nitrogen by eating producers. • 3. Ammonification: Decomposers in soil and water break down nitrogen compounds in ammonium. • 4. Nitrification: Nitrifying bacteria convert ammonium into nitrite and then into nitrate. • Denitrification: Denitrifying bacteria in oxygen poor soil and stagnant water convert nitrate into nitrous oxide and eventually nitrogen gas.

11. Human Impact on Nitrogen Cycle • Human activity can upset the balance of the nitrogen cycling either by removing or adding nitrogen • Destroying forests and plants removes organic nitrogen source • Commercial fertilizer add too many nitrates to the ecosystem which runoff into streams and rivers. • Discharge of human wastes and untreated sewage into rivers and streams can add further nitrogen loads. • Automobile and power plants emit nitrogen dioxide into the atmosphere which reacts with oxygen to form ozone that remains in the atmosphere.

12. The Phosphorus Cycle

13. Phosphorous Cycle • Phosphorous found in soil rock and sediments. • It is release from these rocks forms through the process of chemical weathering.

14. Phosphorous Cycle • 1. Weathering of uplifted rocks contribute phosphates to the land. Some phosphates make their way back to the ocean. • 2. Phosphate fertilizer applied to fields can run off directly into steams, becomes part of a soil pool, or be absorbed by plants. • 3. Excretion by animals and decomposition of both animals and plants release phosphates on land or in water. • 4. Dissolved phosphate precipitate out of solution and contribute to the ocean sediments. Conversion of sediments into phosphate rocks is a very slow process.

15. Human Impact of Phosphorus Cycle • Phosphorus is a limiting nutrient in many aquatic systems which can cause a rapid growth of algae known as algal bloom. • Algal eventually dies initiating a massive amount of decomposition which consumes oxygen. • Fertilizer- continaing runoff and household detergents.

16. The Sulfur Cycle

17. Sulfur cycle • Sulfur cycle involve the atmosphere unlike the phosphorus cycle. • During decomposition in soil and water, decomposers convert sulfates into hydrogen sulfide gas that can escape into the atmosphere, water, soil and sediments. • In soil, various chemosynthetic bacteria can convert hydrogen sulfide back into inorganic sulfates, to sulfuric acid and or sulfur. If iron is present in the soils or sediments wil will react with elemental sulfur to form iron sulfide, which gets incorporated into rocks by geological processes.

18. Sulfur cycle • In water, photosynthetic bacteria and other bacteria can convert hydrogen sulfide into organic and inorganic sulfates. • In the atmosphere, hydrogen sulfide gas quickly breaks down into sulfur dioxide, where it combines with waters vapor to form sulfuric acid. The sulfuric acid precipitates as acid ran thereby returning sulfur to the soil and water. However, acid rain can also kill vegetation and erode rocks.

19. Human impact on Sulfur Cycle • Emission from coal-burning power plants dump large amount of sulfur dioxide and sulfate particles into the atmosphere. Prevailing winds and storms systems carry the particles over vast distance and precipitates acid rain in place far from the source.

20. The Water (Hydrologic) Cycle

21. Water Cycle • 1. Solar energy heats Earth, and causes evaporation • 2. Evaporated water condenses into clouds. • Water returns to Earth as precipitation • Precipitation falling on land is taken up by plants, runs off along the land surface or percolates into the soil and enters the groundwater.

22. Human Activities and the Hydrologic Cycle • Earth is a closed system water can never leave it. • Human activities can alter the water cycle: harvesting tress from a forest can reduce transpiration by reducing plant biomass. Paving over land surface to build road, businesses and homes reduce the amount of percolation that can take place in a given area, increasing runoff and evaporation.

23. Solar Radiation • Albedo • The reflectance of solar energy off earth’s surface • Dark colors = low albedo • Forests and ocean • Light colors = high albedo • Ice caps • Sun provides energy for life, powers biogeochemical cycles, and determines climate

24. Temperature Changes with Latitude • Solar energy does not hit earth uniformly • Due to earth’s spherical shape and tilt Equator (a) High concentration Little Reflection High Temperature Closer to Poles (c) Low concentration Higher Reflection Low Temperature From (a) to (c) In diagram below

25. Temperature Changes with Season • Seasons determined by earth’s tilt (23.5°) ) • Causes each hemisphere to tilt toward the sun for half the year • Northern Hemisphere tilts towards the sun from March 21– September 22 (warm season)

26. The Atmosphere • Content • 21% Oxygen • 78% Nitrogen • 1% Argon, Carbon dioxide, Neon and Helium • Density decreases with distance from earth • Shields earth from high energy radiation

27. Atmospheric Layers • Troposphere (0-10km) • Where weather occurs • Temperature decreases with altitude • Stratosphere (10-45km) • Temperature increases with altitude- very stable • Ozone layer absorbs UV • Mesosphere (45-80km) • Temperature decreases with altitude

28. Atmospheric Layers • Thermosphere (80–500km) • Gases in thin air absorb x-rays and short-wave UV radiation = very hot • Source of aurora • Exosphere (500km and up) • Outermost layer • Atmosphere continues to thin until converges with interplanetary space

29. Atmospheric Circulation • Near Equator • Warm air rises, cools and splits to flow towards the poles • ~30°N&S sinks back to surface • Air moves along surface back towards equator • This occurs at higher latitudes as well • Moves heat from equator to the poles

30. Surface Winds • Large winds due in part to pressures caused by global circulation of air • Left side of diagram • Winds blow from high to low pressure • Right side of diagram High Low High Low High Low High

31. Coriolis Effect • Earth’s rotation influences direction of wind • Earth rotates from East to West • Deflects wind from straight-line path • Coriolis Effect • Influence of the earth’s rotation on movement of air and fluids • Turns them Right in the Northern Hemisphere • Turns them Left in the Southern Hemisphere

32. Coriolis Effect

33. Patterns of Ocean Circulation • Prevailing winds produce ocean currents and generate gyres • Example: the North Atlantic Ocean • Trade winds blow west • Westerliesblow east • Creates a clockwise gyre in the North Atlantic • Circular pattern influenced by Coriolis Effect • North Hemisphere currents swirl to right and South Hemisphere swirl to the left.

34. Patterns of Ocean Circulation Westerlies Trade winds

35. Position of Landmasses Large landmasses in the Northern Hemisphere help to dictate ocean currents and flow Very little land in the Southern Hemisphere

36. Vertical Mixing of Ocean

37. Vertical Mixing of Ocean Water Cold, salty water is denser so it sinks. Ocean conveyor belt-shows the circulation of shallow and deep currents. *goes from cold salty deep sea water from higher to lower latitudes. Effects: regional and possible global climates.

38. Ocean and atmosphere are strongly linked together. Best example is El Nino (ENSO) Trade winds weaken and warm water expands eastward to South America. Warming of surface waters of tropical move in E. Pacific Ocean Ocean Interactions with the Atmosphere

39. Ocean Interaction with Atmosphere- ENSO • El Niño-Southern Oscillation (ENSO) • Effects: • Prevents upwelling (raising ocean currents that transport colder nutrient-laden water to the surface) (pictured right) of nutrient-rich waters off South America • Alters global air currents, directing unusual and sometimes dangerous weather .

40. Normal Conditions • Westward blowing tradewinds keep warmest water in western Pacific

41. ENSO Conditions • Trade winds weaken and warm water expands eastward to South America • Big effect on fishing industry off South America

42. La Nina • Occurs when the surface-water temperature in the eastern Pacific Ocean becomes unusually cool and wastbound trade winds become usnually strong. • Causes wetter winters in The Pacific Northwest, warmer weather in the Southeast and drought conditions in Southwest. Atlantic hurricanes are stronger and more numerous.

43. Weather and Climate • Weather • The conditions in the atmosphere at a given place and time • Temperature, precipitation, cloudiness, etc. • Climate • The average weather conditions that occur in a place over a period of years • Two most important factors: temperature and precipitation

44. Rain Shadows • Mountains force humid air to rise • Air cools with altitude, clouds form, and precipitation occurs (windward side) • Dry air mass moves leeward side of mountain

45. Tornadoes • Powerful funnel of air associated with a severe thunderstorm • Formation • Strong updraft of spinning air forms as mass of cool dry air collides with warm humid air • Spinning funnel becomes tornado when it descends from cloud • Wind velocity = up to 300mph • Width ranges from 1m to 3.2km

46. Tropical Cyclone • Giant rotating tropical storms • Wind >119km per hour • Formation • Strong winds pick up moisture over warm surface waters and starts to spin due to Earth’s rotation • Spin causes upward spiral of clouds • Many names: • Hurricane (Atlantic), typhoon (Pacific), cyclone (Indian Ocean)

48. Internal Planetary Processes • Layers of the earth • Lithosphere • Outermost rigid rock layer composed of plates • Asthenosphere • Lower mantle comprised of hot soft rock

49. Internal Planetary Processes • Plate Tectonics- study of the processes by which the lithospheric plates move over the asthenosphere • Plate Boundary - where 2 plates meet • Divergent • Convergent • Transform

50. Plates and Plate Boundaries