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4.5 Changes in Ecosystems pgs. 113 - 121

4.5 Changes in Ecosystems pgs. 113 - 121. Deforestation. Slash and Burn – the complete clearing of a forest by felling and burning the trees. Deforestation. Clear cutting – the removal of all trees in an area. Deforestation.

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4.5 Changes in Ecosystems pgs. 113 - 121

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  1. 4.5 Changes in Ecosystems pgs. 113 - 121

  2. Deforestation • Slash and Burn – the complete clearing of a forest by felling and burning the trees

  3. Deforestation • Clear cutting – the removal of all trees in an area

  4. Deforestation • Selective cutting – the harvesting of only certain trees from an area

  5. Negative Effects • Soil erosion and runoff into streams increases • Nitrates and other nutrients are carried into streams and ponds, increasing algae growth • Loss of habitat • Replanting can take 80-90 years before trees are large enough to harvest More details can be found on pg 114

  6. Fire • Fire is an important and often helpful cause of change in an ecosystem

  7. Effects of Fire • Creates and maintains a variety of different vegetation types • Essential in the germination of certain seeds • Allows for new growth in an old growth forest

  8. Questions pg. 115 • Do Practice Questions 1-3

  9. Changes in Lake Ecosystems • Oligotrophic Lakes – deep, cold and low in nutrient levels • Eutrophic Lakes – generally shallow, warmer and high in nutrient levels • Eutrophication – the evolution from an oligotrophic lake to an eutrophic lake

  10. Oligotrophic Lake

  11. Mesotrophic Lake

  12. Eutrophic Lake

  13. Water Pollution • Human waste • Fertilizers • Household and industrial products • Thermal energy (heated water) • Water pollution is any physical or chemical change in surface water or ground water that can harm living things • See pg 116 for details

  14. Indicators of Water Quality • Detection of coliform bacteria (naturally occurring bacteria found in the intestines of humans and animals) would also indicate the likelihood of other disease causing bacteria

  15. Biological Oxygen Demand (BOD) • BOD – a measure of the amount of dissolved oxygen needed by decomposers (bacteria) to break down organic matter in a sample of water at 20 C over 5 days • As the number of organisms increases, so does the BOD High numbers of organisms = High BOD High numbers of organisms = Less dissolved oxygen

  16. Question pg. 118 • Do Practice Question #5 and 6

  17. Changes in Alberta Lakes • Watershed – the land that drains toward a lake or other body of water

  18. Effects of Cottage Dwellers on Alberta Lakes

  19. Making sandy beaches increases erosion • Planting lawns increases nitrogen and phosphorus runoff from fertilizers • Removing shoreline plants takes away a filtering system for harmful chemicals moving from the land to the lake, decreases shade and thus affects water temperatures near the shore • Human sewage seeping from outhouses cause increased bacteria activity (less oxygen)

  20. Human sewage seeping from outhouses cause increased bacteria activity (less oxygen)

  21. Questions • Do Practice Questions pg. 120 #7 and 8

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