11. pH measures the acidity of substances, including soil.
14. Modern pesticides are designed to last one growing season and then break down into less harmful substances. Most are water-soluble, so they can be excreted through sweat and urine.
25. (a) The photograph shows clearcutting of a forest.
(b) Students’ answers may vary but could include changes to the habitat by removing the ecosystems many organisms live and function in; change in climate, as less water is released into the atmosphere through the transpiration and the water cycle; change in climate with the release of carbon dioxide into the atmosphere through combustion of wood; pollution, as debris from the forest industry is released into the environment; eutrophication of nearby aquatic ecosystems as nitrates leave the system and cause algal blooms.
26. No, clear water does not necessarily indicate safe drinking water. It could be full of dangerous bacteria, heavy metals, be too acidic, contain pesticides, nitrates, or other chemicals.
27. The most likely cause is runoff of fertilizer from farms that has entered the lake, causing eutrophication.
45. You could include tests for indicators such as the presence of sensitive aquatic organisms, levels of dissolved oxygen (too low and everything dies), biological oxygen demand (really high BOD could mean a source of pollution), pH (too acidic and everything dies), nitrates (do not normally occur in nature, so could indicate pollution), phosphates (too many can cause algal blooms), ammonia (if levels are really high, could mean too much death -- from pollution?). You would test several times a year and in more than one location to compare results.
28. Many pollutants bioaccumulate in the tissues of animals. The pollutants biomagnify through the food chain and eventually collect in very high concentrations in top consumers, where negative effects can be observed.