Unit 8

• Range of Tolerance


  The range within which an organism can survive and thrive, beyond which it will experience physiological stress, limited growth, or even death
• Polar Bear Example


  • Polar bear's range of tolerance depicted in a bell curve
  • Bear is comfortable within optimal range
  • Bear experiences stress and discomfort as it approaches sub-optimal range
  • Outside tolerance range, bear may experience severe physiological stress, limited growth, or even death
• Climate change can cause coral bleaching, leading to the death of coral
• Coral bleaching


  Occurs when coral is stressed, causing it to expel algae and turn white
• Oil spills can have devastating effects on the environment
• Oil


  • Hydrophobic, causing it to spread rapidly on water
  • Can harm bird feathers
  • Can sink to the benthic area, killing species
  • Can release toxins, making it unsafe to fish or consume fish
• Plastics


  • Take forever to break down
  • Can photo-degrade into smaller pieces, attracting small animals
  • Can release toxins as they break down
• Endocrine disruptors


  Can disrupt hormones in the body, leading to birth defects, developmental or reproductive effects, and problems with the immune system
• Point source pollution


  Pollution that is emitted directly from a very identifiable source
• Point source pollution examples

  • Smoke stacks
  • Outflow pipes from industrial facilities
• Non-point source pollution


  Pollution that is more diffuse or spread out
• Non-point source pollution examples

  • Runoff from farm fields carrying fertilizers
  • Nutrient excess in waterways leading to eutrophication
• Eutrophication


  1. Runoff carries nutrients into a waterway

  2. Algae growth increases dramatically

  3. Algae die and decompose, using up oxygen in the water

  4. Low oxygen levels lead to fish and plant die-offs
• Dead zones


  Hypoxic areas where oxygen levels are too low to support life
• Example of dead zone


  • The dead zone in the Gulf of Mexico, formed by nutrients from the Mississippi River watershed
• Near point source


  Biological Oxygen Demand (BOD) is high, Dissolved Oxygen (DO) is low, Fish population is low
• Further downstream


  BOD decreases, DO decreases, Fish population increases
• Farther downstream


  BOD is low, DO is high, Fish population is high
• Bioaccumulation


  The buildup of toxic substances in an organism's tissues
• Biomagnification


  The increasing concentration of toxic substances as they move up the food chain
• Example of bioaccumulation and biomagnification

  • Methyl mercury bioaccumulates in tissues and biomagnifies up the food chain from krill to small fish to medium fish to big fish
• Thermal pollution


  Caused by hot water being released into a cooler water body, affects the well-being of species in the water body, can cause fish to avoid the location and experience physiological stress due to the change in temperature, warmer water holds less oxygen, leading to a lack of oxygen in the water
• Example of thermal pollution


  • Coal-fired and nuclear power plants releasing hot water into the environment
• Sanitary landfills


  • Pits lined with plastic or other barriers to prevent leakage
  • Leachate collection system to collect fluid that accumulates
  • Methane collection to collect methane produced by decomposition
  • Cap and revert to apply a cap to a finalized landfill and potentially revert it to green space
• Incineration


  Burning waste at high temperatures to reduce volume, releases air pollution, may not be a sustainable method in the future
• Recycling


  Reusing materials, but not everything can be recycled, energy-intensive and expensive, but a way to reduce waste
• Sewage treatment


  1. Primary treatment: physical removal of large objects

  2. Secondary treatment: biological treatment using bacteria to break down waste

  3. Tertiary treatment: chemical treatment to remove nutrients and disinfect the water
• Lethal Dose 50 (LD50)


  The dose of a chemical required to kill 50% of a population, used to determine safe and unsafe dosing
• Climate change is expanding the range of diseases, such as West Nile virus, Zika, and malaria
• Pathogens spread more easily in areas with poverty, lack of sanitation, and dirty water
• Laws and Regulations


  • Clean Water Act: Makes it unlawful to discharge pollutants from a point source into navigable waters
  • Safe Drinking Water Act: Protects underground sources of drinking water (aquifers) from contamination
  • RCRA (Resource Conservation and Recovery Act): Monitors hazardous waste from creation to disposal (cradle to grave management)
  • CIRCLA (Superfund): Holds companies responsible for cleaning up hazardous waste
  • Delaney Clause: Bans food additives known to cause cancer in humans or animals