Update on the Bald Eagle

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Update on the Bald Eagle
EFFECT OF DDT

• John Paul Aratari Period 2/3
• AP Biology

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Background

• DDT- used to control insects such as mosquitoes
  and agricultural pests
• DDT is transported by water to areas far from
  where its used, and has rapidly became a global
  problem
• The compound is soluble in lipids- collects in
  the fatty tissues of animals, and its
  concentration is magnified in higher trophic
  levels

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DDT

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Background Continued

• Traces of DDT have been found in nearly every
  organism tested even in human breast milk
• In 1962, American biologist Rachel Carson
  published the book Silent Spring, which alleged
  that DDT caused cancer and harmed bird
  reproduction by thinning egg shells.
• The book resulted in a large public outcry which
  eventually led to the insecticide being banned
  for agricultural use in the USA
• DDT was subsequently banned for agricultural use
  in many countries in the 1970s

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Silent Spring
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Environmental Impacts of DDT

• One of the first signs that DDT was a serious
  environmental problem was a decline in the
  populations of pelicans, ospreys, and eagles,
  birds that feed at the top of food chains.
• Accumulation of DDT in the tissues of birds
  interfered with the deposition of calcium in
  their egg shells
• When these birds tried to incubate their eggs,
  the weight of the parents broke the affected
  eggs, resulting in devastating declines in their
  reproduction rates

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Intro To Biological Magnification

• Organisms acquire toxic substances from the
  environment along with nutrients and water
• Some of the poisons are metabolized and excreted,
  but others accumulate in specific tissues. (Fat)
• Account for endocrine system disruption- Effects
  internal regulation and maintains homeostasis.

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Biological Magnification

• Toxins are harmful because they become more
  concentrated in successive trophic levels of a
  food chain
• This the main reason why DDT has been cited as a
  major reason for the decline of the bald eagle in
  the 1950s and 1960s. Magnification occurs
  because the biomass at any given trophic level is
  produced from a much larger biomass ingested from
  the level below
• Example of Biological Magnification DDT

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Biological Magnification

• DDT and its metabolic products accumulate through
  the food chain, with top level predators, having
  a higher concentration of the chemicals than
  other animals sharing the same environment.
• This happens because when larger animals eat
  smaller animals or prey, they dont just eat one
  or two of these animals during their lifetime,
  sometimes they eat thousands or millions. Not
  only are these animals ingesting their prey,
  theyre also ingesting all of their preys toxins

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Bald Eagle
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THE END