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Published byIris Hardy Modified over 9 years ago
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Fossil evidence indicates that modern humans evolved in East Africa about 200,000 years ago During most of their existence they survived by hunting and gathering *Picture taken from http://www.jantoo.com/cartoons/keywords/scavange
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Agriculture started about 12,000 years ago The development of agriculture gave rise to civilization. http://www.history.com/shows/mankind- the-story-of-all-of-us/videos/mankind-the- story-of-all-of-us-farming http://www.history.com/shows/mankind- the-story-of-all-of-us/videos/mankind-the- story-of-all-of-us-farming
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Early agriculture was mostly subsistence farming Subsistence farming – when the family produces just enough food to support the family unit (without excess intended for sale or trade) Although this early farming method could deplete soil, it did not involved many of the environmentally detrimental techniques that are characteristic of modern farming.
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*Picture taken from http://cnx.org/contents/7ccdfd4e-aa8a-4beb-b05a-9fa2be510152@1/Commercial_and_subsistence_farhttp://cnx.org/contents/7ccdfd4e-aa8a-4beb-b05a-9fa2be510152@1/Commercial_and_subsistence_far
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Agriculture by its very nature requires humans to manipulate the natural environment Examples -plowing, tilling land -fertilizers -pesticides -monocultures -artificial selection -genetically modified organisms
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Pest – a troublesome, destructive, or annoying organism (this definition is from a human’s perspective of course) Pests can cause many problems -can compete with humans for food (destroy crops) -can carry disease (example – malaria and yellow fever) -can have negative effects on native wildlife/environment -can cause damage to residential and commercial property
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Picture of a female mosquito feeding *Picture taken from http://cal.vet.upenn.edu/projects/merial/introduction/intro_2.htm
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Insects (can be killed by insecticides) Fungi (can be killed by fungicides) Mammals (can be killed by rodenticides and other poisons) Nematodes (can be killed by nematicides) Birds (can be killed by avicides) Weeds (can be killed by herbicides) Any organism that “interferes” with human activities can be considered a pest
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*Picture taken from http://npic.orst.edu/pest/learnpest.html
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Introduced species – often become pests Monocultures (growing a single kind of plant over a large area) encourages pest development -provide abundant food supply -often eliminate/reduce natural predators Pesticides – often make the pest problem worst by making the targeted pest stronger and destroying natural predators
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Early pesticides – natural minerals or chemicals, were expensive and had limited success at controlling pests *Picture taken from http://www.awesomelyluvvie.com/2013/03/greyhound-roach-ride.html
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-chlorinated hydrocarbons are a family a pesticides which include the pesticide DDT -discovered during WWI when insects were used to test chemicals (nerve gas) -became the most important group of insecticides *Picture taken from http://www.123rf.com/stock-photo/cockroach.html
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Cheap and easy to use Killed many different kinds of insects Continued to kill insects long after they were applied (persistent) *Picture taken from http://www.123rf.com/stock-photo/cockroach.html
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DDT was the first widely used chlorinated hydrocarbon DDT was banned in the U.S. in 1972 due to its adverse effects on the environment http://www.cbsnews.com/news/the-legacy-of- silent-spring/ http://www.cbsnews.com/news/the-legacy-of- silent-spring/ Bald eagle populations decreased as a result of DDT use. * Picture taken from www.fws.gov
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Persistent vs biodegradable – persistent take a long time to break down in the environment while biodegradable pesticides break down more easily Broad-spectrum vs. selective – broad-spectrum kill many different organisms including the target pest while selective kill the target organism *In North America only 1 out 8 insects is considered a pest!
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Pro – saved millions of lives and billions of dollars worth of crops, protect humans from disease and hunger Con – can affect the natural ecosystem (often times in ways that we can not predict), can cause health problems, often make pests stronger (resistant)
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