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Biological Sciences
Marc Cadotte

CHAPTER 1 THE WEB OF LIFEDeformity and Decline in Amphibian Populations A Case Studyy In the United States misshapen individuals were found in 46 states and in more than 60 species of frogs salamanders and toads In some localities more than 90 of the individuals were deformed Deformed amphibians were also found in Europe Asia and Australia Worldwide it appeared that the frequency of amphibian deformities was on the rise y Adding to the alarm caused by the gruesome deformities were observations beginning in the late 1980s of another disturbing trend global amphibian populations seemed to be in decline By 1993 over 500 populations of frogs and salamanders from around the world were reported to be decreasing in size or under threat of extinction y Scientists were especially worried about amphibians for three reasons First the decline appeared to have started recently across wide regions of the world Second some of the populations in decline were located in protected or pristine regions seemingly far from the effects of human activities Third many scientists view amphibians as good biological indicators of environmental conditions for a number of reasons Amphibians have permeable skin through which pollutants and other molecules can pass with no hair scales or feathers to protect them and their eggs lack shells or other protective coverings Furthermore most amphibians spend part of their lives in water and part on land As a result they are exposed to a wide range of potential threats including water and air pollution as well as changes in temperature and in the amount of ultraviolet UV light in their environment Many amphibians never travel far from their birthplace so the decline of a local population is likely to indicate a deterioration of local environmental conditionsIntroductiony Our activities have transformed nearly half of Earths land surface and have altered the composition of the atmosphere leading to global climate change We have introduced many species to new regions an action that can have severe negative effects on both native species and human economies y Natural systems are driven by the ways in which organisms interact with one another and with their physical environment Thus to understand how natural systems work we must understand ecology the scientific study of how organisms affect and are affected by other organisms and their environmentConcept 11 Events in the natural world are interconnectedConnections in Naturey Events in the natural world can be linked or connected to one another These connections occur as organisms interact with one another and with their physical environment y All organisms are connected to features of their environment For example they all require food space and other resources and they interact with other species and the
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