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Deforestation - main causes
- 1. Logging
- 2. Mining
- 3. Urban development
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Agriculture
- 1. Grazing. (lack of diversity).
- 2. Farming. (lack of diversity).
- 3. Monoculture: Intensive cultivation of a single plant variety over large areas.
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Monoculture
Intensive cultivation of a single plant variety over large areas
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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.
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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.
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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).
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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.
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Release of Toxic -Chemicals
- 1. First Generation Pesticides = heavy metals.
- 2. Second Generation of Pesticides = DDT
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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.
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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.
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Release of Toxic Chemicals – DDT
- 1. Bioaccumulation
- 2. Biomagnification
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Bioaccumulation
Increasing concentrations of potentially toxic substances in living organisms; ingested, but not biodegradable.
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Biomagnification
Increasing concentrations of potentially toxic substances thru food chains; exponentially increasing in toxicity at each level.
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Endangered species
- At risk of extinction throughout all or a significant portion of its range.
- ie: Black footed Ferret
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Threatened species
- Those species that are likely to become endangered in the near future.
- ie: Koala
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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
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Greenhouse effect
Warming of the atmosphere by CO2, CH4, and other gases that absorb infrared radiation (heat), slowing its escape from earth.
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Greenhouse Effect – Solutions
- 1. Reduce deforestation.
- 2. Reduce trees burned after deforestation.
- 3. Reduce burning fossil fuels.
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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 .
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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.
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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!)
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Biodiversity
- All the variety of life.
- 1. Concerns both species richness & relative abundance of different spp that make up a community.
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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.
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Disaster species
Prevail due to the ability to thrive in habitats disrupted by humansExamples: rats, pigeons, and cockroaches
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Biodiversity Crisis - 4 Main Causes
- 1. Habitat Destruction
- 2. Introduced Species3. Population Fragmentation
- 4. Overexploitation
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Habitat Destruction
- a) Urban development
- b) Logging
- c) Mining
- d) Agriculture
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Introduced Species
- Eliminate native spp through predation and competition.
- Example: European rabbits and foxes in Australia
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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.
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Overexploitation
- Animal species whose numbers have been decimated by excessive commercial harvest or sport hunting.
- 1. Overhunting
- 2. Unintentional killing
- 3. Wildlife products
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Overhunting
Whales, American bison, Galapagos tortoises, numerous fishes.
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Unintentional killing
Dolphins, sea turtles, and seabirds in fishing nets
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Wildlife products
Elephant tusks, rhino horn, bear gallbladders
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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
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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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