Transcript Pesticides
Pesticides SNC1D Pest • Pests are living organisms that are not wanted around us. • Examples of pests include unwanted dandelions growing in the lawn; rodents or insects that eat fruits, vegetables or other crop species; micro-organisms that cause disease in forest, fish, or crop resources, etc. • A pest is any organism that man believes is undesirable, has a negative impact on the human environment, or is in competition with human use of a resource, either natural, or cultivated. 4 types of Pesticide • • • • Herbicides: kills plants Insecticides: kills insects Fungicides: kills fungi Bactericides: kills bacteria Early Pesticide Use: • First generation pesticides • the use of toxic inorganic metallic salts such as copper sulfate, lead salts, arsenic, or mercury. • These substances were generally effective against the intended pest, but also created some environmental problems: – they also killed other beneficial organisms, – polluted water and soil resources used by man. – Most early pesticides were non-biodegradable (meaning that they were not broken down within the ecosystem). Therefore, they began to accumulate in the environment, contaminating water and soil resources, eventually poisoning humans. Modern Pesticides: • Second generation pesticides • organic pesticides that were designed to be less toxic to man and more specific toward the intended pests. • Some of these pesticides were fat soluble. This characteristic lead to a problem known as bioaccumulation. • Toxins become more highly concentrated at higher trophic levels. • One example of this problem is illustrated by the damage done to predatory birds as a result of bioaccumulation of DDT. As a result of this problem DDT has been banned from use in North America. • DDT = dichlorodiphenyltrichloroethane Pesticide Resistance • When pest become resistant to pesticides which means the pesticide no longer effects them. Development of pesticide resistance • There is a chance that some pest will have genes that allow them to survive a first application of pesticides. • They are resistant to the pesticide. • The survivors then have offspring which are mostly resistant. • These individuals survive the next spraying. If a similar pesticide is often used, resistant pest will soon make up most of the population. • • 1. Which statement is generally true regarding DDT? a. DDT is not a serious problem since it is biodegradable. b. DDT will kill all the pests it is used against. c. DDT tends to accumulate in the tissues of top predators. d. DDT is water soluble so it is normally excreted in urine. • • • 2. Which statement best describes the problem associated with continued use of the same pesticide? a. The pests are completely eliminated from the ecosystem. b. The pesticide kills a greater number of pests with each application. c. The pesticide kills fewer of the pests with each application. d. Pesticides are generally highly specific and rarely harm beneficial organisms. • • • 3. Which statement regarding early pesticide use is false? a. Early pesticides made use of heavy metals such as mercury. b. Early pesticides contaminated soil and water. c. Early pesticides were biodegradable. d. Early pesticides were toxic to humans. • • • 4. What is the most common problem associated with fat soluble pesticides? a. They tend to contaminate the ground water supply. b. They are highly specific to a single pest species. c. They are prone to biomagnification. d. They must be sprayed more often than water soluble pesticides. • • • 5. Which is most likely to contain the highest concentration of pesticide in its body tissues? a. wheat b. frog eating birds c. frogs d. grasshopppers • • 1. Which statement is generally true regarding DDT? a. DDT is not a serious problem since it is biodegradable. b. DDT will kill all the pests it is used against. c. DDT tends to accumulate in the tissues of top predators. d. DDT is water soluble so it is normally excreted in urine. • • • 2. Which statement best describes the problem associated with continued use of the same pesticide? a. The pests are completely eliminated from the ecosystem. b. The pesticide kills a greater number of pests with each application. c. The pesticide kills fewer of the pests with each application. d. Pesticides are generally highly specific and rarely harm beneficial organisms. • • • 3. Which statement regarding early pesticide use is false? a. Early pesticides made use of heavy metals such as mercury. b. Early pesticides contaminated soil and water. c. Early pesticides were biodegradable. d. Early pesticides were toxic to humans. • • • 4. What is the most common problem associated with fat soluble pesticides? a. They tend to contaminate the ground water supply. b. They are highly specific to a single pest species. c. They are prone to biomagnification. d. They must be sprayed more often than water soluble pesticides. • • • 5. Which is most likely to contain the highest concentration of pesticide in its body tissues? a. wheat b. frog eating birds c. frogs d. grasshopppers Bioaccumulation Effect of Bioaccumulation on Ecosystems • Amphibians are valuable indicators of environmental health because they’re sensitive to chemical changes. • Since the 80s the world amphibian population has declined & birth deformities have increased. • This may be due to: drought, increased UV rays, pollution, habitat loss, parasites & diseases. Amphibians, like this frog, have exhibited drastic changes since the 1980s. Bioaccumulation • Bioaccumulation: a slow build up of chemicals in the bodies of organisms. – If bioaccumulation occurs in a keystone species, it can affect every other organism in its far reaching niches. • Eg. bioaccumulation of PCBs in the B.C. Orcas. – PCBs will affect the reproductive cycles of Orcas until at least 2030, even though they were banned in ‘77. • Chemicals like PCBs and DDT & other insecticides are called persistent organic pollutants (POPs). – POPs contain carbon, & remain in water & soil for many years (like all organic comp) – DDT, even at low levels (5 ppm) causes nervous, immune & reproductive system disorders in animals. – ppm = parts per million Spraying DDT, 1958 Video’s • PCB’s – http://video.nationalgeographic.com/video/pla yer/news/culture-places-news/norway-bearapvin.html • Pesticides and heavy metals Biomagnification Biomagnification: the consumers in each trophic level receive larger doses of accumulated chemicals than the one before it. The bioaccumulation of PCBs begins with the absorption of the chemicals by microscopic plants and algae. See page 94 • Heavy metals also bioaccumulate. – Lead, cadmium & mercury are the most dangerous. • Lead is not considered safe at any level, it can cause anemia, nervous & reproductive system damage. • Cadmium is toxic to earthworms & causes many health problems in fish. • Cadmium causes lung diseases, cancer, nervous & immune system damage in humans (exposure to cigarette smoke). Mercury enters ecosystems through burning of fossil fuels, waste incineration, mining & the manufacture of batteries. Coal burning adds 40% of the mercury released. Mercury bioaccumulates in the brain, heart & kidneys of many animals (Fish bioaccumulate mercury, adding risk for any organisms eating fish). Reducing the effects of chemical pollution • If chemicals are trapped in the soil, they cannot enter the food chains as easily. • Bioremediation: micro-organisms or plants are used to help clean up, and are then removed from the ecosystem. – Eg. The oil industry will often use bacteria to “eat” oil spills. Biomagnification • http://www.youtube.com/watch?v=E5P-UoKLxlA Bioaccumulation • http://www.youtube.com/watch?v=wkpFIW6ke5 E&feature=PlayList&p=D35F0BB0E6936BB3&pl aynext=1&index=2 Bioremediation • http://www.youtube.com/watch?v=pSpjRPWYJP g • http://www.youtube.com/watch?v=zmSaNqMpfC s