1. The development of reliable agriculture fostered the rapid growth in human populations. This event fostered development of permanent settlements and cities. The major cultural event that eventually took place was the specialization of professions.
2. Undeveloped countries have the larger population of individuals under the age of 15. The significance of this is that they have a greater number of potentially reproductive individuals who can increase their population at an even faster rate. As a further effect, people in developed countries will be a much smaller proportion of the whole population, while still holding the majority of the world's wealth.
3. Rice, wheat, and corn supply more than half of the human energy requirements. Just over 100 species of plants supply over 90% of all calories consumed.
4. Genetic engineering can yield crop plants that are resistant to pests, pesticides, and rotting, providing for a greater overall yield.
5. The chief benefit of nuclear power is that it uses a plentiful resource. The chief drawbacks are: (1) it is not cheap, when the costs of plant construction are included. (2) Nuclear safety is not guaranteed with current reactor design-and what if a nuclear-powered country like France were attacked with conventional weapons in a war? (3) Spread of nuclear weapons material and technology will create a more dangerous world. (4) Nuclear waste disposal problems have not been solved, nor has a single nuclear power plant yet been decommissioned successfully.
6. The amount of CO2 has increased since the advent of industrialization because of the burning of fossil fuels and the destruction of forests. The greenhouse effect is the result of CO2 and other gases in the atmosphere preventing heat from radiating into space. This produces global climatic warming; rising sea levels; increased growth of some kinds of plants, which alters community relationships; and the drying out of the best farmlands, thus decreasing their productivity.
7. Chlorinated hydrocarbons were banned in the United States due to their deleterious effects (such as thinned egg shells in birds), as well as their tendency to "bioaccumulate," or accumulate in the tissues of organisms that consumed contaminated material. Foreign imports may still contain traces of these contaminants, however, which is how they can get back into the country.
8. Acid rain forms when the sulfur compounds (SO2 and other sulfates) from industrial pollution combine with water vapor in the air to form an acid, which subsequently precipitates back to earth. It is difficult to regulate, because acid rain theoretically "generated" in one country can actually fall to Earth in another.
9. Ozone is O3 and it is formed as light stimulates the dissociation of O2 by ultraviolet radiation. Decreasing the earth's ozone layer results in an increased rate of human skin cancers and damage to the ocean's phytoplankton and other photosynthetic organisms. The primary cause is probably manufactured chemicals, especially chlorofluorocarbons. High levels of ozone are also deleterious because they lead to damage to human lungs and to citrus plants.
10. Shifting agriculture in the tropics is promoting deforestation, along with its loss of biodiversity and root systems that keep soil erosion at bay. Forests are being decimated for agricultural space and for use of the wood. Any forest that does survive will have a greatly reduced diversity of life, and perhaps a tenuous hold on the soil.
11. First, we have no ethical, moral, or aesthetic right to decimate such valuable communities. Second, the organisms comprising diverse ecosystems give us everything we have: food, medicines, clothing, shelter. It is stupid to eliminate the source of many of our needs. Third, the biotic and abiotic components of an ecosystem interact. Without the biotic (living, organismal) component, the abiotic (nonliving: water, rocks, soil, nutrients, etc.) will become inexorably altered as their biotic components are decimated to consequences we can't even predict in some cases.
12. The goals at environmental science are operational ones-to solve the problems created by modern society's impact on the environment. Eliminating pollution, conserving biodiversity, protecting groundwater and topsoil-these are but a few specific goals. The tools environmental scientists use are Ecology, Geology, Political Science, and Economics; environmental problems typically impact a broad range of scientific and social issues. The five components to solving environmental problems are assessment, risk analysis, public education, political action, and follow-through.