This Is an Advantage Because Fewer Butterflies Are Eaten So More Butterflies Live to Reproduce

Bioaccumulation

Bioaccumulation – process in which toxins are ingested by an organism at a rate greater than they are eliminated

e.g. monarch butterfly ingests toxins from milkweed and stores the toxins in its tissues so the butterfly is poisonous to eat

-this is an advantage because fewer butterflies are eaten so more butterflies live to reproduce

-bioaccumulation of man made toxins can be devastating to a species (health problems, death)

Biomagnification – increase in the concentration of a toxin as it moves from one trophic level to the next

e.g. DDT (dichloro-diphenyl-trichloroethane)

- an agricultural insecticide once used in N. America

- run-off from land ® absorbed by algae in the water ® microscopic animals ate the algae ® small fish ate microscopic animals ® birds ate the fish

-at each trophic level the concentration of DDT in the tissues of the organisms increased

-at high concentrations the DDT affected reproduction in fish eating birds

-DDT banned in the 1970s

-populations of DDT-vulnerable birds slowly increased in numbers in Canada

e.g. PCBs (polychlorinated biphenyls)

-previously used by industries

-entered water, air and soil

-peregrine flacons and bald eagles were affected by both DDT and PCBs

-after PCBs were banned they were brought back form the brink of extinction by breeding captive birds and having humans help raise them in boxes on nesting cliffs or tall downtown buildings

** 1962 Silent Spring by Rachel Carson

-warned the public of the dangers associated with pesticide use

- numerous case studies documenting the harmful effects of chemical pesticides have -- she explains how in many instances the pesticides have done more harm than good in eradicating the pests

- many of the long-term effects that these chemicals may have on the environment, as well as on humans, were still unknown

-Silent Spring "brought environmental issues to the attention not just of industry and government; it brought them to the public, and put our democracy itself on the side of saving the Earth" (Al Gore, 1994).

Source - http://www.bofep.org/pollutio.htm