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feeding on each size prey is simply the energy content of the prey minus the energy costs of pursuing and handling it. According to optimal foraging theory, natural selection favors individuals whose foraging behavior is as energetically efficient as possible. In other words, animals tend to feed on prey that maximize...
. take is the result of genetic differences, but there are some exceptions. For example, one study found that female zebra finches that were particularly successful in maximizing net energy intake tended to have offspring that were similarly successful. Because birds were removed from their mothers before they left the...
may take the form of increased food intake, exclusive access to mates, or access to refuges from predators. Studies of nectar-feeding birds like hummingbirds and sunbirds provide an example (figure 27.5). A bird benefits from having the exclusive use of a patch of flowers because it can efficiently harvest the nectar ...
they expend will have an advantage in survival and reproduction over animals that behave in less efficient ways. 27.2 Reproductive behavior involves many choices influenced by natural selection. Searching for a place to nest, finding a mate, and rearing young involve a collection of behaviors loosely referred to as re...
20 0 Female body weight FIGURE 27.6 The advantage of male mate choice. Male mormon crickets choose heavier females as mates, and larger females have more eggs. Thus, male mate selection increases fitness. ness is rarely limited by the amount of sperm they can produce. By contrast, each reproductive event for females i...
the evolution of structures used in combat with other males, such as a deer’s antlers and a ram’s horns, as well as ornamentation used to “persuade” members of the opposite sex to mate, such as long tail feathers and bright plumage (figure 27.7a). These traits are called secondary sexual characteristics. Intrasexual S...
racting mates with long feathers is common in bird species such as the African paradise whydah (a) and the peacock (b), which show pronounced sexual dimorphism. (c) Female peahens prefer to mate with males with greater numbers of eyespots in their tail feathers. 558 Part VII Ecology and Behavior The Benefits of Mate Ch...
survive with such a handicap. By choosing a male with the largest handicap, the female is ensuring that her offspring will receive these quality genes. Of course, the male offspring will also inherit the genes for the handicap. For this reason, evolutionary biologists are still debating the merits of this hypothesis. ...
(one male mates with more than one female; figure 27.9), and polyandry (one female mates with more than one male) are aspects of male and female reproductive strategy that concern how many mates an individual has during the breeding season. Like mate choice, mating systems have evolved to maximize reproductive fitness...
. DNA fingerprints are 560 Part VII Ecology and Behavior FIGURE 27.9 Female defense polygyny in bats. The male at the lower right is guarding a group of females. so variable that each individual’s is unique. Thus, by comparing the DNA of a man and a child, experts can establish with a relatively high degree of confiden...
a completely different strategy. They do not maintain territories, but hang around the edge of the territories of large males. Just at the end of a male’s courtship, when the female is laying her eggs and the territorial male is depositing sperm, the smaller male will dart in and release its own sperm into the water, ...
fingerprinting study in redwinged blackbirds. Fractions indicate the proportion of offspring fathered by the male in whose territory the nest occurred. Arrows indicate how many offspring were fathered by particular males outside of each territory. Nests on some territories were not sampled. Chapter 27 Behavioral Ecolo...
, by hanging around an area, such individuals may inherit the territory when the established breeders die. Similarly, alarm callers may actually be beneficial by causing other animals to panic. In the ensuing confusion, the caller may be able to slip off undetected. Detailed field studies in recent years have demonstra...
les, and each of their children would receive half of these, of which half on the average would be in common: one-half × one-half × onehalf = one-eighth. Eight first cousins would therefore pass on as many of those alleles to the next generation as Haldane himself would. Hamilton saw Haldane’s point clearly: natural se...
Belding’s ground squirrel give alarm calls when they spot a predator such as a coyote or a badger. Such predators may attack a calling squirrel, so giving a signal places the caller at risk. The social unit of a ground squirrel colony consists of a female and her daughters, sisters, aunts, and nieces. Males in the col...
sex determination, called haplodiploidy, leads to an unusual situation. If the queen is fertilized by a single male, then all 564 Part VII Ecology and Behavior FIGURE 27.12 Reproductive division of labor in honeybees. The queen (shown here with a red spot painted on her thorax) is the sole egglayer. Her daughters are ...
cases, individuals may benefit directly from social living. For example, a bird that joins a flock may receive greater protection from predators. As flock size increases, the risk of predation decreases because there are more individuals to scan the environment for predators (figure 27.13). A member of a flock may als...
out to mate, and returns to assume “rule” of the hive. The leafcutter ants provide another fascinating example of the remarkable lifestyles of social insects. Leafcutters live in colonies of up to several million individuals, growing crops of fungi beneath the ground. Their mound-like nests are underground “cities” co...
divided according to the type of social group they form. One set of species lives in the forest and builds camouflaged, solitary nests. Males and females are monogamous; they forage for insects to feed their young. The second group of species nests in colonies in trees on the savanna. They are polygynous and feed in f...
female or “queen,” who has one or two male consorts. The workers, consisting of both sexes, keep the tunnels clear and forage for food. Social behavior in vertebrates is often characterized by kin-selected altruism. Altruistic behavior is involved in cooperative breeding in birds and alarm-calling in mammals. Human So...
inheritance and are passed from generation to generation by tradition. Nonetheless, cultural inheritance is as valid a way to convey adaptations across generations as genetic inheritance. Human cultures are also extraordinarily diverse. The ways in which children are socialized among Trobriand Islanders, Pygmies, and ...
than in the past. Chapter 27 Behavioral Ecology 567 Chapter 27 Summary 27.1 Evolutionary forces shape behavior. • Many behaviors are ecologically important and serve as adaptations. • Foraging and territorial behaviors have evolved because they allow animals to use resources efficiently. www.mhhe.com/raven6e www.bioco...
. 6. In vertebrate societies, what are the costs to an individual who makes an alarm call? Based on research in ground squirrels, which individuals are most likely to make alarm calls, and what benefits do they receive by doing so? 568 Part VII Ecology and Behavior Part VIII The Global Environment Identifying the Envir...
amphibians, like this Cascades frog (Rana cascadae), are declining in numbers in many regions chemical pollutants, and to increased levels of UV-B radiation produced by ozone depletion. While numerous experiments performed under laboratory conditions have demonstrated the power of these factors to produce developmenta...
affects of UV-B on amphibian development had already shown a significant increase in embryonic mortality in some amphibian species, and not in others. Why only in some? Perhaps behaviors shared by many amphibian species might lead to an increased susceptibility to damage from UV-B radiation, behaviors such as laying e...
one thing, frog species that are not sensitive to UV-B have very high photolyase activity levels. Evaluating 10 different species, Blaustein’s team found a strong correlation between species exhibiting little UV-B radiation effects and higher levels of photolyase activity in developing eggs and embryos. In these exper...
at each step. Ecological Pyramids. The biomass of a trophic level is less, the farther it is from the primary production of photosynthesizers. Interactions among Different Trophic Levels. Processes on one trophic level can have effects on higher or lower levels of the food chain. 28.4 Biodiversity promotes ecosystem s...
, for example, first enter water from weathered rock, then pass into organisms when they drink the water. Materials pass from the organisms that first acquire them into the bodies of other organisms that eat them, until ultimately, through decomposition, they complete the cycle and return to the nonliving world. The Wa...
upper, unconfined portion of the groundwater constitutes the water table, which flows into streams and is partly accessible to plants; the lower confined layers are generally out of reach, although they can be “mined” by humans. The water table is recharged by water that percolates through the soil from precipitation ...
into the atmosphere falls back to earth as rain. Where forests are cut down, the organismic water cycle is broken, and moisture is not returned to the atmosphere. Water drains away from the area to the sea instead of rising to the clouds and falling again on the forest. As early as the late 1700s, the great German exp...
fossil fuels such as oil or coal. In addition to the roughly 700 billion metric tons of carbon dioxide in the atmosphere, approximately 1 trillion metric tons are dissolved in the ocean. More than half of this quantity is in the upper layers, where photosynthesis takes place. The fossil fuels, primarily oil and coal, ...
. Because of the activities of such organisms in the past, a large reservoir of ammonia and nitrates now exists in most ecosystems. This reservoir is the immediate source of much of the nitrogen used by organisms. Nitrogen-containing compounds, such as proteins in plant and animal bodies, are decomposed rapidly by cert...
present only in certain kinds of rocks. As phosphates weather out of soils, they are transported by rivers and streams to the oceans, where they accumulate in sediments. They are naturally brought back up again only by the uplift of lands, such as occurs along the Pacific coast of North and South America, creating upw...
1963 by Herbert Bormann of the Yale School of Forestry and Environmental Studies, Gene Likens of the Institute of Ecosystem Studies, and their colleagues. These studies have yielded much of the available information about the cycling of nutrients in forest ecosystems. They have also provided the basis for the developm...
0 1965 1966 1967 1968 Year FIGURE 28.7 The Hubbard Brook experiment. (a) A 38-acre watershed was completely deforested, and the runoff monitored for several years. (b) Deforestation greatly increased the loss of minerals in runoff water from the ecosystem. The red curve represents nitrate in the runoff water from the ...
on their leaves, converting it to food energy. In especially productive systems, this percentage may be a little higher. When these plants are consumed by other organisms, only a portion of the plant’s accumulated energy is actually converted into the bodies of the organisms that consume them. Several different levels...
at trophic level 2. Animals that eat plant-eating animals, such as shrews, are carnivores and are at trophic level 3 (secondary consumers); animals that eat carnivorous animals, such as hawks, are tertiary consumers at trophic level 4. Detritivores use all trophic levels for food. stored by growth. An invertebrate typ...
normally produce between 1500 and 3000 grams of organic material per square meter per year. By contrast, corresponding figures for other communities include 1200 to 1300 grams for temperate forests, 900 grams for savanna, and 90 grams for deserts (table 28.1). Secondary Productivity The rate of production by heterotro...
feces, about 33%, 165 J, is used to fuel cellular respiration, and about 17%, 85 J, is converted into insect biomass. Only this 85 J is available to the next trophic level. Primary producer Primary consumer Secondary consumer Tertiary consumer FIGURE 28.11 A food chain. Because so much energy is lost at each step, foo...
for humans, the amount of smelt biomass is at least five times greater than that available in trout, although humans prefer to eat trout. Chapter 28 Dynamics of Ecosystems 581 Carnivore Herbivore 1 11 Plankton (4,000,000,000) (a) Pyramid of numbers Decomposer (5 grams/ square meter) Second-level carnivore (1.5 grams/s...
with zooplankton consuming phytoplankton so quickly that the phytoplankton (the producers at the base of the food chain) can never develop a large population size. Because the phytoplankton reproduce very rapidly, the community can support a population of heterotrophs that is larger in biomass and more numerous than t...
that prevented fish from entering. In some of the enclosures, brown trout were added, whereas other enclosures were left without large fish. After 10 days, the number of invertebrates in the trout enclosures was one-half of that in the controls (figure 28.14). In turn, the biomass of algae, which invertebrates feed up...
. I have watched the face of many a new wolfless mountain, and seen the south-facing slopes wrinkle with a maze of new deer trails. I have seen every edible bush and seedling browsed, first to anemic desuetude, and then to death. I have seen every edible tree defoliated to the height of a saddle horn.” Many similar exa...
. At low levels of productivity, herbivore populations cannot be maintained. Above some threshold, increases in productivity lead to increases in herbivore biomass; vegetation biomass no longer increases with productivity because it is converted into herbivore biomass. Similarly, above another threshold, herbivore biom...
always so simple. In some cases, species may simultaneously operate on multiple trophic levels, such as the jaguar which eats both smaller carnivores and herbivores, or the bear which eats both fish and berries. Nature is often much more complicated than a simple, linear food chain, as figure 28.9 indicates. Ecologist...
words, plots with more species were less affected. In a related experiment, when seeds of other plant species were added to different plots, the ability of these species to become established was negatively related to species richness. More diverse communities, in other words, are more resistant to invasion by new spe...
species took up more nitrogen from the soil, leaving less in the rooting zone. The increased amount of nitrogen absorption is an indicator of increased growth, increased biomass, and thus increased productivity. fact, they argue—the more species you add to a mix, the greater the probability that you will add a highly ...
Spatial Heterogeneity. Environments that are more spatially heterogeneous—that contain more soil types, topographies, and other habitat variations—can be expected to accommodate more species because they provide a greater variety of microhabitats, microclimates, places to hide from predators, and so on. In general, th...
geographic gradient in numbers of species correlated with latitude has been reported for plants and animals, including birds (figure 28.23), mammals, reptiles. Why Are There More Species in the Tropics? For the better part of a century, ecologists have puzzled over the cline in species diversity from the arctic to the ...
, a marked increase in the number of species occurs as one moves toward the tropics. Fewer than 100 species are found at arctic latitudes, while more than 600 species live in southern Central America. Predictability. There are no winters in the tropics. Tropical temperatures are stable and predictable, one day much lik...
increase—the more species on an island, the greater the likelihood that any given species will perish. As a result, at some point, the number of extinctions and colonizations should be equal and the number of species should then remain constant. Every island of a given size, then, has a characteristic equilibrium numb...
distance from the mainland and when the extinction rate is affected by size of the island. Species richness is positively correlated with island size and inversely correlated with distance from the mainland. (c) The effect of distance from a larger island—which can be the source of colonizing species—is readily appare...
? Which organisms carry it out? 3. How is the phosphorus cycle different from the water, carbon, nitrogen, and oxygen cycles? What are the natural sources for phosphorus? 4. What effect does deforestation have on the water cycle and overall fertility of the land? • Activity: Nutrient Cycle • Activity: Carbon Cycle • Ec...
major groups of organisms originated and are still represented in the sea. Marine Ecosystems. The communities of the ocean are delineated primarily by depth. Freshwater Habitats. Like miniature oceans, ponds and lakes support different communities at different depths. Productivity of Freshwater Ecosystems. Freshwater ...
, morphological, or behavioral mechanisms to maintain homeostasis. The beetle in figure 29.2 is using a behavioral mechanism to cope with drastic changes in water availability. Other animals and plants simply conform to the environment in which they find themselves, their bodies adopting the temperature, salinity, and ...
alcohols that protect their cell membranes from freeze damage. Morphology. Animals that maintain a constant internal temperature (endotherms) in a cold environment have adaptations that tend to minimize energy expenditure. Many other mammals grower thicker coats during the winter, utilizing their fur as insulation to ...
lizard from northern Europe, but the northern lizards are capable of running, capturing prey, and digesting food at cooler temperatures at which desert lizards would be completely immobilized. Many species also exhibit adaptations to living in areas where water is scarce. Everyone knows of the camel, and other desert ...
resulting patterns of oceanic circulation. Together these factors dictate local climate, and so determine the amounts and distribution of precipitation. The Sun and Atmospheric Circulation The earth receives an enormous quantity of heat from the sun in the form of shortwave radiation, and it radiates an equal amount o...
temperate regions because the sun’s rays arrive almost perpendicular to regions near the equator. Near the poles the angle of incidence of the sun’s rays spreads them out over a much greater area, providing less energy per unit area (figure 29.5a). 594 Part VIII The Global Environment 60 30 Equator 30 Westerlies North...
the Earth’s Rotation Related to these bands of north-south circulation are three major air currents generated mainly by the interaction of the earth’s rotation with patterns of worldwide heat gain. Between about 30° north latitude and 30° south latitude, the trade winds blow, from the east-southeast in the southern he...
that resembles that of the Mediterranean region. So-called Mediterranean climates are found in portions of Baja, California, and Oregon; in central Chile; in southwestern Australia; and in the Cape region of South Africa. In all of these areas, the prevailing westerlies blow during the summer from a cool ocean onto wa...
3500 m Polar ice Tundra Taiga Elevation Temperate forest Tropical rain forest North pole Equator Latitude Sea level Elevation FIGURE 29.9 Elevation affects the distribution of biomes much as latitude does. Biomes that normally occur far north and far south of the equator at sea level also occur in the tropics at high ...
these very localized climatic conditions can be very different from those of the overhead atmosphere. Gardeners spread straw over newly seeded lawns to create such a moisture-retaining microclimate. The great deserts and associated arid areas of the world mostly lie along the western sides of continents at about 30° n...
.10 The distribution of biomes. Each biome is similar in structure and appearance wherever it occurs on earth. 598 Part VIII The Global Environment Biomes and Climate Many different environmental factors play a role in determining which biomes are found where. Two key parameters are available moisture and temperature. ...
s species of terrestrial plants and animals—more than 2 million species! In a single square mile of tropical forest in Rondonia, Brazil, there are 1200 species of butterflies—twice the total number found in the United States and Canada combined. The communities that make up tropical rain forests are diverse in that eac...
where they exploit food that may be abundant seasonally. Temperate Grasslands Halfway between the equator and the poles are temperate regions where rich grasslands grow. These grasslands once covered much of the interior of North America, and they were widespread in Eurasia and South America as well. Such grasslands a...
spruce, hemlock, and fir) extends across vast areas of Asia and North America. Coniferous trees are ones with leaves like needles that are kept all year long. This ecosystem, called taiga, is one of the largest on earth. Here, the winters are long and cold, and most of the limited precipitation falls in the summer. Bec...
gyres (figure 29.15), which move around the subtropical zones of high pressure between approximately 30° north and 30° south latitude. These gyres move clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. The ways they redistribute heat profoundly affects life not only in the oceans bu...
local fishermen named this Christmas current El Niño (literally, “the child,” after “the Christ Child”). Now, though, the term is reserved for a catastrophic version of the same phenomenon, one that occurs every two to seven years and is felt not only locally but on a global scale. Scientists now have a pretty good id...
ños are now fairly clear, what triggers them still remains a mystery. Models of these weather disturbances suggest that the climatic change that triggers El Niño is “chaotic.” Wind and ocean currents return again and again to the same condition, but never in a regular pattern, and small nudges can send them off in many...
, thus allowing populations to diverge and encouraging local specialization and species formation. A patchy environment may also contribute to species formation there; deep-sea ecologists find evidence that fine but nonetheless formidable resource barriers arise in the deep sea. Another conjecture is that the extra bil...
ocean floor that drops to depths where light does not penetrate is called the abyssal zone. The Neritic Zone The neritic zone of the ocean is the area less than 300 meters below the surface along the coasts of continents and islands. The zone is small in area, but it is inhabited by large numbers of species (figure 29...
from shore. FIGURE 29.19 Diversity is great in coastal regions. Fishes and many other kinds of animals find food and shelter among the kelp beds in the coastal waters of temperate regions. Chapter 29 The Biosphere 605 The Pelagic Zone Drifting freely in the upper waters of the pelagic zone, a diverse biological commun...
that the number of species that live at great depth is quite high. Most of these animals are only a few millimeters in size, although larger ones also occur in these regions. Some of the larger ones are bioluminescent (figure 29.20a) and thus are able to communicate with one another or attract their prey. 606 Part VII...
About 40% of the world’s photosynthetic productivity is estimated to occur in the oceans. The turnover of nutrients in the plankton is much more rapid than in most other ecosystems, and the total amounts of nutrients are very low. Freshwater Habitats Freshwater habitats are distinct from both marine and terrestrial on...
the periphery of the lake, where attached algae and their insect herbivores live. An open-water surface (limnetic) zone lies across the entire lake and is inhabited by floating algae, zooplankton, and fish. A dark, deep-water (profundal) zone overlies the sediments at the bottom of the lake and contains numerous bacte...
surface water warms up. When it warms back to 4°C, it again mixes with the water below. This process is known as spring overturn. When lake waters mix in the spring and fall, nutrients formerly held in the depths of the lake are returned to the surface, and oxygen from surface waters is carried to the depths. Freshwat...
invertebrate populations. This situation can be remedied if the continual input of phosphorus can be diminished. Given time, lakes can recover and return to prepollution states, as happened with Lake Washington pictured in figure 29.24. The Productivity of Wetlands Swamps, marshes, bogs, and other wetlands covered wit...
poles, descending at about 30° north and south latitude. Because the air falls in these regions, it is warmed, and its moisture-holding capacity increases. The great deserts of the world are formed in these drier latitudes. 2. Why are the majority of great deserts located near 30° north and south latitude? Is it more ...
6. Does much diversity occur in the abyssal zone? How are such ecosystems supported in the absence of light? 7. What is the difference between a eutrophic and an oligotrophic lake? Why have humans increased the frequency of lakes becoming eutrophied? • Four Seasons • Global Air Circulation • Rainshadow Effect • Weathe...
its view were talking, hundreds of thousands of cars were struggling through traffic, hearts were being broken, babies born, and dead people buried. Our futures and those of everyone on the planet are linked to the unseen millions in this photograph, for we share the earth with them. A lot of people consume a lot of f...
(excluding China) are growing at an annual rate estimated in 1995 to be about 2.2%. For every person living in an industrialized country like the United States in 1950, there were two people living elsewhere; in 2020, just 70 years later, there will be five. As you learned in chapter 24, the age structure of a populat...
increased family planning efforts and the increased economic power and social status of women. While the U.N. applauds the United States for leading the world in funding family planning programs abroad, some oppose spending money on international family planning. The opposition states that money is better spent on imp...
million inhabitants. Chapter 30 The Future of the Biosphere 613 30.2 Improvements in agriculture are needed to feed a hungry world. The Future of Agriculture One of the greatest and most immediate challenges facing today’s world is producing enough food to feed our expanding population. This problem is often not appre...
) Grain amaranths (Amaranthus spp.) were important crops in the Latin American highlands during the days of the Incas and Aztecs. Grain amaranths are fast-growing plants that produce abundant grain rich in lysine, an amino acid rare in plant proteins but essential for animal nutrition. (b) The winged bean (Psophocarpus...
modified rice, for example, is no longer deficient in ascorbic acid and iron, providing a major improvement in human nutrition. Other modifications allow crops to tolerate irrigation with salt water, fix nitrogen, carry out C4 photosynthesis, and produce substances that deter pests and diseases. Genetically modified c...
tons by 1992 and continuing to fall each year as the intensity of the fishing increases. The development of new kinds of food, such as microorganisms cultured in nutrient solutions, should definitely be pursued. For example, the photosynthetic, nitrogen-fixing cyanobacterium Spirulina is being investigated in several ...
that blew the reactor apart. The explosion and heat sent up a plume 5 kilometers high, carrying several tons of uranium dioxide fuel and fission products. The blast released over 100 megacuries of radioactivity, making it the largest nuclear accident ever reported; by comparison, the Three Mile Island accident in Penn...
useful lives (about 25 years). In 1997, over 35 plants were more than 25 years old, and not one has been safely decommissioned, its nuclear wastes disposed of. A third challenge is the need to guard against terrorism and sabotage, because the technology of nuclear power generation is closely linked to that of nuclear ...
312 ) 61 60.5 60 59.5 59 58. Average mean global temperature, 1958–1996 '58 '60 '62 '64 '66 '68 '70 '72 '74 '76 '78 58 '80 '82 '84 '86 '88 '90 '92 '94 '96'96 '97 '98 '99 '2000 Year (1900s) FIGURE 30.5 The greenhouse effect. The concentration of carbon dioxide in the atmosphere has steadily increased since the 1950s (b...
is a broad ribbon of water that runs through the heart of Europe. From high in the Alps that separate Italy and Switzerland, the Rhine flows north across the industrial regions of Germany before reaching Holland and the sea. Where it crosses the mountains between Mainz and Coblenz, Germany, the Rhine is one of the mos...
of the plastic that has ever been produced is still with us, in one form or another. Collectively, it constitutes a new form of pollution. Widespread agriculture, carried out increasingly by modern methods, introduces large amounts of many new kinds of chemicals into the global ecosystem, including 618 Part VII The Gl...
high in the atmosphere, where winds would disperse and dilute it, carrying the acids far away. Environmental effects of this acidity are serious. Sulfur introduced into the upper atmosphere combines with water vapor to produce sulfuric acid, and when the water later falls as rain or snow, the precipitation is acid. Na...
that of natural rainwater, which has a pH of about 5.6. FIGURE 30.8 Damage to trees at Clingman’s Dome, Tennessee. Acid precipitation weakens trees and makes them more susceptible to pests and predators. Chapter 30 The Future of the Biosphere 619 The Ozone Hole The swirling colors of the satellite photos in figure 30....
, the approximately 3% drop that has already occurred worldwide is estimated to have increased skin cancers by as much as 20%. A type of skin cancer (melanoma) is one of the more lethal human diseases. UV CCl3F → Cl + CCl2F UV creates oxygen free radicals: O2 → 2O Cl atoms and O free radicals interact with ozone: 2Cl...
tend to grow on more fertile soils, they were exploited by humans a long time ago. Now the rain forests, which grow on poor soils, are being destroyed. In the mid-1990s, it is estimated that only about 5.5 million square kilometers of tropical rain forest still exist in a relatively undisturbed form. This area, about ...
to learn more about the construction of sustainable agricultural ecosystems that will meet human needs in tropical and subtropical regions. The ecological concepts we have been reviewing in the last three chapters are universal principles. The undisturbed tropical rain forest has one of the highest rates of net primar...
. The public, through its elected officials selects a course of action and implements it. Choices are particularly difficult to implement when environmental problems transcend national boundaries. 5. Follow-through. The results of any action should be carefully monitored to see whether the environmental problem is bein...
at the University of Washington in Seattle, W. T. Edmondson, noted that his research students were reporting filamentous blue-green algae growing in the lake. Such algae require plentiful nutrients, which deep freshwater lakes usually lack—the sewage had been fertilizing the lake! Edmondson, alarmed, began a campaign ...
ice age over 12,000 years ago. We should not waste this treasure, for we cannot replace it. In most areas of the United States, local governments exert relatively little control over the use of groundwater. As a result, a large portion is wasted watering lawns, washing cars, and running fountains. A great deal more is...

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