Bio 004,CH20, College of the Desert

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Mattyj1388
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Bio 004,CH20, College of the Desert
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2011-07-18 16:29:55
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Chapter20 COD Human Impact Environment deforestation
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  1. Deforestation - main causes
    • 1. Logging
    • 2. Mining
    • 3. Urban development
  2. Agriculture
    • 1. Grazing. (lack of diversity).
    • 2. Farming. (lack of diversity).
    • 3. Monoculture: Intensive cultivation of a single plant variety over large areas.
  3. Monoculture
    Intensive cultivation of a single plant variety over large areas
  4. Introduced Species
    • Spp which humans move from their native region to a new geographic region (exotic species).
    • 1. Number over 50,000 in the US.
    • 2. Prey on native species.
    • 3. Out-compete native species for resources.
    • 4. $130 billion in damage control.
  5. Chemical Cycles –
    Carbon
    • 1. Increased burning of fossil fuels.
    • 2. Deforestation, increased burning of wood.
    • Impact: Increased levels of CO2 in the atmosphere resulting in global warming.
  6. Chemical Cycles –
    Nitrogen/Phosphorous
    • 1. Dumping of N/P from sewage treatment plants into rivers & streams.
    • 2. Use of N/P-based fertilizers in agriculture & landscaping (nitrates & phosphates).
    • Impact: Impact: Increased levels of N/P in lakes & streams resulting in heavy algae growth (eutrophication).
  7. Chemical Cycles –
    Water
    • 1. Deforestation leads to decreased transpiration (source of atmospheric moisture)
    • 2. Pumping of groundwater for crop irrigation.
    • Impact: Periods of drought and depletion of groundwater supplies.
  8. Release of Toxic -Chemicals
    • 1. First Generation Pesticides = heavy metals.
    • 2. Second Generation of Pesticides = DDT
  9. First Generation Pesticides = heavy metals
    • 1. Mercury, lead, arsenic, etc.
    • 2. Accumulate in the environment - usually toxic or carcinogenic (cancer-causing).
    • 3. Pests develop resistance making these pesticides ineffective in a short time.
  10. Second Generation of Pesticides = DDT
    • 1. Initially toxic to insects, while seemingly nontoxic to mammals.
    • 2. Inexpensive to produce (synthetic, organic).
    • 3. Covered a broad spectrum of pests.
    • 4. Persisted in the environment.
  11. Release of Toxic Chemicals – DDT
    • 1. Bioaccumulation
    • 2. Biomagnification
  12. Bioaccumulation
    Increasing concentrations of potentially toxic substances in living organisms; ingested, but not biodegradable.
  13. Biomagnification
    Increasing concentrations of potentially toxic substances thru food chains; exponentially increasing in toxicity at each level.
  14. Endangered species
    • At risk of extinction throughout all or a significant portion of its range.
    • ie: Black footed Ferret
  15. Threatened species
    • Those species that are likely to become endangered in the near future.
    • ie: Koala
  16. Carbon Dioxide Emissions
    • 1. Accelerated since the Industrial Revolution (1850).
    • 2. Increased burning of fossil fuels.
    • 3. Deforestation &increased burning of wood.
    • Impact: Increased levels of CO2 in the atmosphere resulting in global warming
  17. Greenhouse effect
    Warming of the atmosphere by CO2, CH4, and other gases that absorb infrared radiation (heat), slowing its escape from earth.
  18. Greenhouse Effect – Solutions
    • 1. Reduce deforestation.
    • 2. Reduce trees burned after deforestation.
    • 3. Reduce burning fossil fuels.
  19. Ozone layer
    Thin, protective layer of O3 located 17 – 25 km above earth’s surface ; absorbs UV radiation, preventing much of it from reaching organisms in the earth’s biosphere .
  20. Depletion of Atmospheric Ozone – Cause
    • 1. Accumulation of chlorofluorocarbons (CFC’s - refrigerants, propellants, etc.).
    • 2. Chlorine reacts with ozone – especially over Antarctica – resulting in holes and thinning ozone.
  21. Depletion of Atmospheric Ozone – Effects
    • Impact: Increase in incidence of skin cancers and cataracts among humans.
    • Impact: Damaging effects on phytoplankton & plants. (bottom of food chain!)
  22. Biodiversity
    • All the variety of life.
    • 1. Concerns both species richness & relative abundance of different spp that make up a community.
  23. Loss of Species
    • 1. Rebound of an endangered spp is unlikely due to human habitat destruction and bio-diversity degradation
    • 2. Disaster species: Prevail due to the ability to thrive in habitats disrupted by humansExamples: rats, pigeons, and cockroaches.
  24. Disaster species
    Prevail due to the ability to thrive in habitats disrupted by humansExamples: rats, pigeons, and cockroaches
  25. Biodiversity Crisis - 4 Main Causes
    • 1. Habitat Destruction
    • 2. Introduced Species
    • 3. Population Fragmentation
    • 4. Overexploitation
  26. Habitat Destruction
    • a) Urban development
    • b) Logging
    • c) Mining
    • d) Agriculture
  27. Introduced Species
    • Eliminate native spp through predation and competition.
    • Example: European rabbits and foxes in Australia
  28. Population Fragmentation
    • Splitting, con-sequent isolation of portions of pops. by habitat fragmentation and degradation.
    • a) Reduction in pop. size → reduction in gene flow/genetic diversity.
  29. Overexploitation
    • Animal species whose numbers have been decimated by excessive commercial harvest or sport hunting.
    • 1. Overhunting
    • 2. Unintentional killing
    • 3. Wildlife products
  30. Overhunting
    Whales, American bison, Galapagos tortoises, numerous fishes.
  31. Unintentional killing
    Dolphins, sea turtles, and seabirds in fishing nets
  32. Wildlife products
    Elephant tusks, rhino horn, bear gallbladders
  33. Why Biodiversity Matters - 3 Main Reasons
    • 1. Ethical and aesthetic reasons.
    • 2. Dependence upon spp for food, shelter, clothing, oxygen, etc
    • 3. 25% of all pharmaceuticals contain substances derived from plants
  34. Biodiversity “Hot Spots”
    • Relatively small areas with exceptional concentrations of spp.
    • Many spp in hot spots are endangered or threatened.
    • Comprise less than 1.5% of earth’s total land mass, but home to 33% of all plant and animal spp.

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