Presentation on theme: "By Jennifer Cunningham, Katie Tang, and Robert Rock A Brief Review of Chapters 11, 12, & 13 in Silent Spring by Rachel Carson."— Presentation transcript:
By Jennifer Cunningham, Katie Tang, and Robert Rock A Brief Review of Chapters 11, 12, & 13 in Silent Spring by Rachel Carson
Gardening is now firmly linked with the super poisons. In 1960 the Florida State Board of Health found it necessary to forbid the commercial use of pesticides in residential areas. Weed and bug killing chemicals are hidden under brand names. Never suggesting that they are harmful. A constant stream of new gadgets make it easier to use poisons on lawns and gardens, thus creating public water to become contaminated.
Excessive use of poisons such as DDT on lawns and crop fields can cause illness and even death if exposed to too much. Most DDT found in the human body enters through the food we eat. The existence of chemical residues on the food we eat is played down by the industry.
Toxins can be concentrated in successive trophic levels of food webs. A process called biological magnification.
Why Aren’t We Protected? Food and Drug Administration only has control over foods shipping in interstate commerce, and there are not enough inspectors on staff. Toxins can not be broken down by microorganisms and other detritivores. Meaning the toxins stay with in the environment for years or even decades. The longer food remains in storage, the greater the danger of contamination. The chemical industry recognizes the frequent misuse of insecticides and the need for education of farmers, however refuses to do anything about it.
Carson’s Suggested Solutions First is the elimination of tolerances on highly toxic chemicals. A vigilant and aggressive Food and Drug Administration, with a greatly increase of spectators. The ultimate answer is to use less toxic chemicals so that public hazard of their misuse is greatly reduced. Public education on the nature of the chemicals is greatly needed Explore non-chemical methods.
Eskimos on the far Arctic shores of Alaska were found to have no DDT or other toxins in there system at all. In fact, the only sign of pesticide was in two white owls from Point Hope that had migrated.
Chapter 12: The Human Price “Today we are concerned with a different kind of hazard that lurks in our environment-a hazard we ourselves have introduced into our world as our modern way of life has evolved.”
Ecology Vs. Environmentalism Environmentalism Advocating for the protection or preservation of the natural environment. Ecology Often complicated and delicate relationships between organisms and the environment. To address environmental problems, we need to understand ecology.
Where do pesticides fit into the picture of environmental disease? Contaminate: Soil Water Food “..they have the power to make our streams fishless and our gardens and woodlands silent and birdless.”
Population Growth “For the population as a whole, we must be more concerned with the delayed effects of absorbing small amounts of the pesticides that invisibly contaminate our world.” Population Ecology is the study of populations in relation to the environment. The biological effects of chemicals are cumulative over long periods of time, and the hazard to the individual may depend on the sum of the exposures received throughout his lifetime. The major forces affecting population growth-birth rates and death rates-can be measured in many populations to predict how the populations will change in size over time.
Idealized survivorship curves: Types I, II, and III A graphic way of representing the data in a life table is to draw a survivorship curve. Survivorship Curves can be classified into three general types: 1.Type1 – relatively flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age-groups. 2.Type 2- intermediate, with a constant death rate over the life span. 3.Type 3- drops sharply at the left of the graph, representing very high death rates for the young, but then flattens out as death rates decline for those who have survived to a critical age. Figure1
The Problem of ecology, of interrelationships, of interdependence Figure2: Examples of terrestrial and marine food chains Figure3: An antarctic marine food web Decomposers are not shown Arrows trace energy and nutrients “A change in one point, in one molecule even, may reverberate throughout the entire system to initiate changes in seemingly unrelated organs and tissues.” Energy decreases as you travel up the chain.
What is DDT? DDT is soluble in lipids, it collects in the fatty tissues of animals, and its concentration is magnified in higher trophic level. 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 the food chains. The accumulation of DDT in the tissues of these birds interfered with the deposition of calcium in their eggshells, a trend that may have already begun because of other environmental contaminants. Birds that feed at the top of the food chain come in contact with DDT. Lay eggs and try to incubate them. The weight of the parents break the shells of affected eggs. Catastrophic declines in their reproduction rates.
Chapter 13: Through a Narrow Window Life is a very complicated thing and the effects pesticides have on living organisms can be difficult to understand when viewed from the big picture. It is not until one looks closer, at the building blocks of life, that the effect pesticides have on living things can be understood. The most basic unit of an organism that can still be called living is the cell. It is within each individual cell that the processes of life take place. The foods we eat go to cells so that they can make energy for the entire body. Proteins and carbohydrates are broken down to create immense amounts of energy.
The creation of energy occurs in the mitochondria of a cell. Here the energy created is stored in the form of ATP (adenosine triphosphate). ATP is used for energy storage in all living things large or small. The reason ATP is used for energy storage is its ability to shift one of its phosphate groups to another substance. If the mitochondria were incapable of creating ATP the energy they produce would be lost. The efficiency of creating and keeping the bond for the third phosphate group is vital for organisms to survive.
Without ATP sperm cells can’t swim to fertilize egg cells and fertilized egg cells do not have the energy to divide and develop into new born animals. Sadly this is exactly what pesticides attack. Insecticides such as phenols and chlorinated hydrocarbons break the third phosphate bond and rob cells of vital energy This attack on the basics of life is what makes pesticides so dangerous. Affecting a single cell wouldn’t make much of a difference, but the fact that a process that occurs within every cell is being affected causes the problem to be magnified.
The most dangerous thing about pesticides is not their disruption of cellular development. It is their disruption of the transmission of genetic information from one generation to the next. Certain pesticides can destroy chromosomes in some plants and change genetic codes in others. This affect on the genetic information of organisms causes mutations that can cause serious birth defects in the next generation. This danger is not limited to only plants and animals. Humans too can fall victim to genetic mutation at the hands of pesticides stored in the body.
That’s the review of chapters 11, 12, &13. Any questions?
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