Lewis/Life - Review of Key Concepts

Review of Key Concepts - Chapter 44

Effects of human activities on the environment are difficult to predict because many complex factors interact.
Environmentalism is the philosophy of living in harmony with the global ecosystem. Environmental problems can affect the entire biosphere.
Air pollutants include heavy metals, fossil fuel emissions, photochemical smog, and fine particulates.
Acid precipitation forms when sulfur and nitrogen oxides from pollution react with water in the upper atmosphere to form hydrochloric and sulfuric acids. Acidification of lakes harms many organisms and changes aquatic communities. In coniferous forests, acid precipitation kills leaves and acidified soil releases aluminum, which robs roots of essential calcium and magnesium and stunts growth, as excess nitrogen stimulates trees to grow. The conflicting signals stress the trees.
Use of chlorofluorocarbon compounds has thinned the ozone layer, which protects life from UV radiation.
The greenhouse effect results from CO2 and other gases trapping infrared radiation near the earth's surface. Agriculture, industry, burning fossil fuels, and destruction of tropical rain forests generate greenhouse gases. The greenhouse effect may contribute to global warming.
Pollutants of aquatic ecosystems include polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and heavy metals. Erecting dams and levees and introducing nonnative species alters river ecosystems. Deposition of sediments and nutrients from development is eutrophying Lake Tahoe. Preserving estuaries is important because they are breeding grounds for many species. Heavy metals and other industrial wastes contaminate ocean sediments and foul beaches. Nutrient discharges into coastal waters stimulate phytoplankton blooms that produce toxins. Plastic and oil contaminate surface waters.
Poor agricultural practices are destroying tropical and temperate forests. Desertification reflects natural drought as well as poor agricultural practices.
The diversity-stability hypothesis states that an ecosystem with many diverse species is better able to survive a threat. The role of species in the ecosystem is important in ecosystem stability.