Name_______________________________Date__________________________
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BIOACCUMULATION in Ecosystems
S2-1-03: Describe bioaccumulation and explain its potential impact in a food web.
A great example of bioaccumulation in our everyday ecosystems is related to pesticides. Pesticides were developed
in the 1940’s to reduce “pests” using things such as insect repellents, rat poisons, flea and tick sprays, powders and
pet collars, kitchen laundry and bathroom disinfectants and sanitizers, products that kill mildews and mold, weed
killers and some swimming pool chemicals.
Many pesticides work by attacking the nervous system of insects. Herbicides work by inhibiting the growth of
roots, interfering with photosynthesis, or causing the plant to grow so fast it can’t sustain itself.
The issue with pesticides is that the chemicals stay inside affected organisms and are passed on to their predators
or the decomposers that eat their dead bodies (bioaccumulation). Also, chemical pesticides have the same limiting
problem as antibiotics; the organisms they are designed to kill can develop resistance to them. Increasingly
widespread applications of pesticides lead to shorter periods of effectiveness before resistance limits their
usefulness.
TAKE A STAND: the use of chemical pesticides in City Parks
On your way home from school, you notice that workers are spraying insecticide on the grass and bushes
of some parks in Winkler. The mosquitoes have been bad this year and it would be nice to be outside
without getting eaten alive, but this is the park your little siblings play at. They crawl in the grass and put
things in their mouths. This makes you wonder how dangerous the chemicals are, how long it takes for
them to break down in the environment and why they are doing this during the middle of the day.
Your community is also worried. You learn there will be a public meeting on this topic and feel you can
contribute with your knowledge of pesticides. There are two opposing positions on this issue. To prepare
for the meeting, list all the possible supporting points that each side could present.
Pro: Chemical pesticides should be
used in city of Winkler parks
Cons: Chemical pesticides should be
banned from city parks in Winkler
Name_______________________________Date__________________________
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In real life, many compromises are made. Describe a compromise position in this issue. Under what
conditions could/should pesticides be used?
COMPROMISE: Pesticides may be used under certain conditions
Questions:
1. What are some possible short-term benefits of pesticides?
2. How might a fat-soluble pesticide (Such as DDT) be transferred through an ecosystem? Hint: use
bioaccumulation and trophic levels to answer this
3. Forested regions of Canada are currently being invaded by Spruce budworms. What are some
possible reasons pesticides have not wiped them out entirely?