Ecology by peter stiling pdf free download

Your list has reached the maximum number of items. Please create a new list with a new name; move some items to a new or existing list; or delete some items. Ecology : theories and applications. Ecology theories and applications. All rights reserved. Please sign in to WorldCat Don't have an account? Remember me on this computer. File Name: ecology by peter stiling pdf. Principles of Ecology - Organisms and the Environment Part 1. Ecology : theories and applications.

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Telangana movement and state formation book in english. The first book of adam and eve by rutherford platt. More Filters. These factors affect the rep … Expand. View 1 excerpt, cites background. Living in a predation matrix : Studies on fish and their prey in a Baltic Sea coastal area.

This thesis was written within the framework of a biomanipulation project where young-of-the-year YOY pikeperch Sander lucioperca were stocked to a Baltic Sea bay to improve water quality throu … Expand. Extinctions in Ecological Communities : direct and indirect effects of perturbation on biodiversity. Horizontally acquired mutualisms, an unsolved problem in ecology?

While ecologists are interested in species richness for its own sake, a link also exists between species richness and community function, for example, the ability to extract soil nutrients or to produce biomass. Ecologists generally believe that, for any given habitat, species-rich communities func- An ecosystem is a living, biotic community and its nonliving abiotic environment. Ecosystems ecology deals with the flow of energy and cycling of nutrients among organisms within a community and between organisms and the environment.

Understanding this flow of energy and nutrients requires knowledge of feeding relationships between species, called food chains. The second law of thermodynamics states that in every energy transformation, free energy is reduced because heat energy is lost from the ecosystem in the process.

There is, therefore, a unidirectional flow of energy through an ecosystem, with energy dissipated at every step. An ecosystem needs a recurring input of energy from an external source—in most cases, the sun—to sustain itself. In contrast, chemicals such as nitrogen and phosphorus do not dissipate and constantly cycle between abiotic and biotic components of the environment, often becoming more concentrated in organisms higher in the food chain.

Global changes are affecting ecological processes at all these scales. In the next section, we discuss the main elements of change. The average life span of a species in the fossil record is around 4 million years.

To calculate the current extinction rate, we could take the total number of species estimated to be alive on Earth at present, around 10 million, and divide it by 4 million, giving an average extinction rate of 2. These figures suggest that as human numbers increase, more and more species go extinct.

If background extinction rates were 10 times higher than the rates perceived from the fossil record, then extinctions among the 4, or so living mammals today would be expected to occur at a rate of one every years. For birds, the background extinction rate would be two species every years. No one disputes, however, that the extinction rate for species in recent times has been far higher than this.

In the past years, approximately 20 species of mammals and over 40 species of birds have become extinct Figure 1. The term biodiversity crisis is often used to describe this elevated loss of species. Conservation biology studies how to protect the biological diversity of life at all levels. Many scientists believe that the rate of species loss is higher now than during most of geological history. Growth of the human population is thought to have led to the increase in the number of extinctions of other species Figure 1.

The reason is that humans are responsible for many elements of global change. To understand the threats to life on Earth in more modern times, it is essential for ecologists to examine the role of human activities in the extinction of species. In this section, we examine the factors that are currently threatening species with extinction.

While we do not know all the threats to life on Earth, habitat destruction, introduced species, direct exploitation, and pollution have been major human-induced threats.

Wilson has referred to these threats using the acronym HIPPO, habitat destruction, introduced species, pollution, population human , and overharvesting, though in truth, overpopulation by humans drives the other four mechanisms. Habitat destruction was the most important threat. Second was invasive species, which threatened almost half the endangered species in the U. Pollution was also important, especially for freshwater species such as fish, mussels, and amphibians.

Overexploitation hunting and collecting was of considerable importance for mammals, birds, reptiles, and some plants. Are results from the rest of the world similar? Worldwide data have not yet been collected, except for birds, which show similar trends to the United States.

Deforestation, the conversion of forested areas to nonforested land, is a prime cause of the extinction of species Figure 1. While tropical forests are probably the most threatened, with rates of deforestation in Africa, South America, and Asia varying between 0. From data in Wilcove, et al. Why is this? Figure 1. Cascade mountains near Seattle, Washington, In terms of wildlife use, oaks are among the most valuable trees in North America. At least species of birds and mammals include acorns in their diets, and for many species of wildlife, the annual acorn crop is a major determinant of their abundance.

Most woodpeckers, as well as many other types of birds, nest in holes that they excavate in trees, and their food usually consists of insects collected on or in trees. The ivory-billed woodpecker, a Campephilus principalis, the largest in North America and an inhabitant of wetlands and forests of the southeastern U.

In , the woodpecker was supposedly sighted in the Big Woods area of eastern Arkansas by John Fitzpatrick and colleagues This nestling was photographed in Louisiana in This Apapane, Himatione sanguinea, is one of the few remaining honeycreeper species. This resulted in egg cracking and increased chick mortality. A normal egg, on the left, is darker and thinner than the DDT affected egg, on the right. More land has been converted to agriculture since than in the 18th and 19th centuries combined.

The scouring of land to plant agricultural crops can create soil erosion, increased flooding, declining soil fertility, silting of the rivers, and desertification. Wetlands also have been drained for agricultural purposes and have been filled in for urban or industrial development. In the U. Urbanization, the development of cities on previously natural or agricultural areas, is the most human-dominated and fastest-growing type of land use worldwide, and it devastates the land more severely than practically any other form of habitat degradation.

Most often the species are introduced for agricultural or landscaping purposes or as sources of timber, meat, or wool, and they need humans for their continued survival.

Others, such as plants, insects, or marine organisms, are unintentionally transported via the movement of cargo by ships or planes. Regardless of the way they have been transported, some introduced species become invasive species, spreading naturally and outcompeting native species for space and resources see Feature Investigation. One hundred and forty-two introduced species of vertebrates have self-sustaining populations in the wild.

These include many species, such as ring-necked pheasants, Phasianus colchicus, which were brought over by hunters, and species such as parrots, which were introduced by pet owners. Of the most invasive weeds in the United States, over half were brought in for gardening, horticulture, or landscape purposes.

These include purple loosestrife, Lythrum salicaria, and Japanese honeysuckle, Lonicera japonica, in the Northeast; Kudzu, Pueraria lobata, in the Southeast; Chinese tallow, Sapium sebiferum, in the South; and leafy spurge, Euphorbia esula, in the Great Plains.

We can break down the interactions between introduced and native species into competition, predation, and parasitism disease.

For example, introduced Norway maple, Acer platanoides, tolerates very shady conditions and outcompetes many plant species in the central and northeastern United States. Th This is known as biological control. However, new n ew w research ressearc on the population ecology of diffuse knapweed, w eed d, Centaurea Cent diffusa, an invasive Eurasian plant that has h ass eestablished staablis itself in many areas of North America, sugggests essts a different diffe reason for the success of invasive species.

Researchers R eseearc Ragan Callaway and Erik Aschehoug 20 0 h hypothesized yp that the roots of Centaurea secrete powerful p ow werfu ul to toxins, called allelochemicals, that kill the roots off other o ottherr species, sp allowing Centaurea to proliferate.

To ttest esst their theiir hypothesis, h Callaway and Aschehoug collected sseeds eeedss off three th native Montana grasses, Junegrass, Koelerria ia a cristata; crristtata Idaho fescue, Festuca idahoensis; and Bluebunch wheatgrass, Agropyron spicata; and grew each of b uncch w he with and without the exotic Centaurea species tthem heem both bo oth w 1. As hypothesized, Centaurea depressed the Figure Fiigu ure 1. When the experiments were with grasses native to Eurasia, Koeleria laersrrepeated ep peaated d w Festuca ssenii, en nii,, Fe estuc ovina, and Agropyron cristatum, the growth off each species was inhibited, but to a significantly lesser o eaach spe degree d eggreee tthan han the Montana species were.

Ass a fu further test of their hypothesis, Callaway and A Aschehoug A sccheeho oug modified their experiments by adding activated the soil, which absorbs the chemical excreted by ccarbon arrbo on tto o th Centaurea tthe hee C entaur roots. With activated carbon, the Montana species ggrass raass sp pecie increased in biomass compared to the previous whereas the Eurasian species did not.

The o uss eexperiments xpeerim rresearchers esseaarch hers concluded that C. This study on the population biology off an o n int introduced trod plant has changed the way we think about why w hy ssuch ucch sp species succeed, and could affect the way we think aabout bo outt th hem in the future.

Parasitism and disease carried by introduced organisms have also been important in causing extinctions. Add activated carbon to some pots. Three months after sowing seeds, the plants are harvested, dried, and weighed. Biomass of native grasses is depressed by C. Conceptual level C. Collect seeds of grasses from Eurasia and plant with and without C. Biomass of Eurasian grasses is not depressed as much as Montana grasses. Addition of activated carbon does not increase biomass.

Two remarkable populations of North American birds, the passenger pigeon and the Carolina parakeet, were hunted to extinction by the early 20th century.

Flock sizes were estimated to be over 1 billion birds. It may seem improbable that the most common bird on the continent could be hunted to extinction for its meat, but that is just what happened. The flocking behavior of the birds made them relatively easy targets for hunters, who used special firearms to harvest the birds in quantity. In in Michigan alone, over 1. The Carolina parakeet, Conuropsis carolinensis, the only species of parrot native to the eastern U.

Gaseous pollutants include carbon monoxide, carbon dioxide CO2 , sulfur dioxide, and nitrogen oxides, most of which come from the burning of fossil fuels. Increasing CO2 levels have already lowered the pH of the ocean by 0.

At increased pH, many calcifying organisms which produce shells or plates will be negatively impacted. Some models predict that by , oceans may be too acidic for corals to calcify. A variety of chemicals are applied to agricultural crops to kill pests and many of these have nontarget effects on wildlife. DDT is a case in point also look ahead to Figure In the s and s, DDT was a commonly used pesticide against a variety of agricultural pests and disease-carrying insects such as mosquitoes.

Accumulation in food chains resulted in high levels of DDT in top predators such as birds of prey. Here DDT interfered with calcium deposition of eggs, resulting in cracked eggs, poor hatching, and lower population densities Figure 1. Aquatic pollutants include numerous pesticides that run off into lakes and rivers from agricultural fields.

Freshwater aquatic systems are perhaps most at risk from pollution from both pesticides and fertilizers containing high levels of nitrogen and phosphorous. These nutrients can cause rapid increases in the growth of algae, which can kill many other forms of life look ahead to Chapter Perhaps the single most important pollutant, however, is carbon dioxide because of its effect on global warming. A poignant example of human excess in hunting was the dodo, Raphus cucullatus, a flightless bird native only to the island of Mauritius that had no known predators.

A combination of overexploitation and introduced species led to its extinction within years of the arrival of humans. Many species of valuable plants have also been severely reduced for their human uses, including West Indian mahogany, Swietenia mahogani, in the Bahamas, and Lebanese Cedar, Cedrus libani, which in Lebanon has been reduced to a few scattered forest remnants.

Rare cacti and orchids have also been threatened by collectors, who seek to own a rare organism or to profit from its sale. Taxa Figure 1. As noted at the beginning of this chapter, global warming has been implicated in the dramatic decrease in the population sizes of frog species in Central and South America. What types of organisms are most threatened with extinction? According to data from the International Union for Conservation of Nature and Natural Resources, amphibians are now the most threatened group of organisms, with mammals a fairly close second Figure 1.

Because of their large habitat requirements, large mammals are especially prone to extinction from habitat destruction while many species of cats are threatened from overexploitation because of their fur and pelts. Pearson and Callaway showed how gall flies, introduced to control knapweed in the western United States, provide a food subsidy for deer mice, allowing populations to increase.

What other effects might this have on the local community? The flies lay their eggs inside the flowerheads and create a tumorlike swelling called a gall, inside of which the fly larvae feed. The hope was that flowerhead production would be reduced and, thus, the spread of the weed.

Unfortunately, seed reductions have not been enough to control the plant. As a result, extensive knapweed and gall fly populations now coexist in many states Figure 1. Dean Pearson and Ragan Callaway showed that deer mice, Peromyscus maniculatus, feed on knapweed galls, and the increased gall production has provided a food subsidy, enabling deer mice populations to double in size.

This is troubling because deer mice are a reservoir of Sin Nombre hantavirus, which causes the deadly hantavirus pulmonary syndrome in humans. Mice testing positive for hantavirus were over three times more abundant in the presence of gall-infested knapweed than in areas where it was absent.

This story has at least two lessons. First, unless biological control agents effectively reduce their target populations, releasing these agents may do more harm than good. Second, it is important to take into account the many complex interactions between species in nature. The chapters that follow provide more evidence of this process. It is important to note that a hypothesis is never really proven. We may conduct further hypothesis testing and fail to disprove a hypothesis.

After many such tests, biologists may accept that a hypothesis is true. For example, Charles Darwin formulated the theory of evolution. In science, the term theory describes an idea or set of ideas that explain a vast amount of data and are well supported by the evidence. This contrasts with the nonscientific or everyday usage of the word theory that connotates a more casual idea, a guess almost, that may explain an observation.

For example, one student might propose a theory that the reason why another student is missing from class is because he is at the beach. Hypothesis testing often takes the form of the experimental or comparative method. In ecology, as in biology, in If rejected, then formulate new hypothesis Figure 1.

In the late 16th-century Europe, it was generally thought that heavier objects fell faster than lighter objects.

The Italian scientist Galileo tested this hypothesis with an experiment. He dropped objects of different mass from the top of the Leaning Tower of Pisa. Galileo found that the objects fell at the same rate, regardless of their mass, thus disproving the hypothesis. The comparative method requires collecting data on two groups that are then compared. A classic example is the effect of smoking on lung cancer in humans. How do ecologists go about studying their subject?

As an ecologist, you are charged with finding out what causes outbreaks of locusts, a type of grasshopper that periodically erupts in Africa and other parts of the world, destroying crops and other vegetation.

Leave other groups unprotected. The rains trigger plant growth but subsequent drought concentrates grasshoppers into dense groups. The bumping of grasshoppers causes increased serotonin production and the grasshoppers become darker, stronger, more mobile, and are known as locusts Figure 1. But what keeps them from increasing their numbers in normal conditions? To find out, you might first draw up a possible web of interactions between the factors that could affect locust population size Figure 1.

In your study of locusts, you might begin by careful observation of the organism in its native environment. You can analyze fluctuations of locust population size and determine if the populations vary with fluctuations in other phenomena, such as levels of parasitism, predator abundance, or food supply. You count locust numbers and numbers of b Figure 1. More plant biomass means more available food and increased locust numbers.

We can draw a line of best fit b to represent this relationship. In c , the relationship between locust numbers and predation levels might be so weak that we would not have much confidence in a linear relationship between the variables.

You notice that locust numbers appear to be affected by numbers of bird predators and that an inverse relationship between predator numbers and locust numbers exists. As predator numbers increase, locust numbers decrease. If you plotted these observations graphically, the resulting graph could look like that depicted in Figure 1.

However, if the points were not highly clustered, as in Figure 1. Many statistical tests are used to determine whether or not two variables are significantly correlated. In this book, unless otherwise stated, graphs like Figure 1. We call this type of relationship a significant correlation. Since locust density shows a negative linear relationship with predation, we say that locust density is negatively correlated with predation. Ecologists have to be cautious when forming conclusions based on correlations.

For example, large numbers of locusts could be associated with large, dense plants. We might conclude from this that food availability controls locust density. However, an alternative conclusion would be that large, dense plants provide locusts refuge from large bird predators, which cannot attack them in the dense interior. Although it would appear that biomass affects locust density by providing abundant food, in actuality, predation could still be the most important factor affecting locust density.

Thus, correlation does not always mean causation. For this reason, after conducting observations, ecologists usually turn to experiments to test their hypotheses. Reduced predation might be achieved by putting a cage made of chicken wire over and around bushes which normally contain locusts and birds, so that birds are denied access but the locusts can come and go as they please.

You could then look at locust survivorship over the course of a week or two. If predators are having a significant effect, then removing them should cause locust numbers to remain unchanged. Thus, you would have two groups: a group of locusts with predators denied access the experimental group , and a group of locusts with predators still present the control group , with equal numbers of locusts in both groups at the start of the experiment.

Any differences in locust population density in the future would be due solely to differences in predation. Performing an experiment several times is called replication.

You might replicate the experiment 5 times, 10 times, or even more. At the end of the replications, you would sum the total number of living locusts, divide the sum by the number of replications, and calculate the mean. The smaller the bars, the tighter the replicate values are around the mean and, usually, the more significant the differences are between the treatment and control groups.

Standard deviations and standard errors are calculated using the values of all the replicates, and the smaller the lines, the closer these replicate values tend to be.

Large differences in replicates lead to large standard deviations and reduce our faith in the repeatability of the results. The two bars represent the average number of locusts where predators are removed experimental and where predators are not removed control. The vertical lines standard deviations or standard errors give an indication of how tightly the individual replicate results are clustered around the mean.

The shorter the lines, the tighter the cluster of replicates, and the more confidence we have in the result. In the control group, which still allows predator access, the numbers surviving might be 2, 4, 7, 5, 3, 6, 11, 4, 1, and 3, with a mean of 4.

Without predators, the mean number of locusts surviving would therefore be almost double the mean number surviving with predators. Your data analysis would give you confidence that predators were indeed the cause of the changes in locust numbers. The results of such experiments can be illustrated graphically by a bar graph Figure 1. Ecologists use a variety of tests to determine whether these differences are statistically significant.

You might notice that in some graphs there are vertical lines around the mean. These lines represent a measure of the spread of the points around the mean. Two different measures are the standard error of the mean and the standard deviation.

The standard error is the standard deviation 1. Laboratory experiments allow the most exact regulation of factors such as light, temperature, and moisture, while only the factor of interest is varied—such as increasing nitrogen availability to plants in pots by adding fertilizer.

The biotic community represented in a laboratory experiment is simplified, however, so conclusions based on laboratory results are limited. Laboratory experiments are best used to study the physiological responses of individual organisms rather than the dynamics of reproducing populations. Field experiments are conducted outdoors and have the advantage of operating on natural rather than artificially contrived populations or communities.

The most commonly used manipulations include the local elimination or addition of competitors, predators, or herbivores.

Density of the target species can then be monitored to see whether it increased or decreased with the treatment, relative to controls.

Charles Darwin used a field experiment to demonstrate that the introduction of grazing animals increases the number of plant species on a lawn. The number of species is increased because grazers often eat the most common species, preventing these species from outcompeting other species, whose numbers then increase.

Field experiments commonly manipulate species through the use of tools, such as cages or fences to keep predators or herbivores in or out. Such manipulations are unlikely to be generated by nature itself. Sometimes natural events like severe droughts, freezes, or floods provide the best opportunity to study the effects of environmental extremes in a field setting.

Such natural extremes are often referred to as natural experiments. Natural experiments are usually the sole technique for following the time path of an environmental change beyond a few decades.

Weather is frequently shown to be of vital importance in influencing the population densities of many species, but we cannot easily manipulate the weather. Natural experiments involving volcanic explosions or hurricanes commonly provide the only data on these subjects.

However, natural experiments are not true experiments in that they are not replicated nor do they have controls. Abbreviated from Diamond, Field experiment Natural experiment 1. Regulation of independent variables High Medium None 2. Maximum temporal scale Low 3. Maximum spatial scale Low Low High If bars do not overlap zero, treatment is significant.

Scope range of Low manipulations Medium High 5. Realism Low High High 6. Effect size is measured as the variable, d. Each point is the mean of a given number of studies n is given in the bar. The strengths and weaknesses of these different types of experiments are outlined in Table 1. For example, the spatial scale of laboratory experiments is likely to be limited to the size of a constant-temperature laboratory room, around 0.

Natural experiments, however, can operate on much larger scales. These constraints frequently lead to low levels of replication and then to what is known as a type I error: the declaration of a hypothesis to be false when it is actually true.

The experiment may be said to have low statistical power. For example, suppose that fertilization of plants increases herbivore densities, but such increases can be detected only by performing ten replicates of an experiment in which we add fertilizer to plants. If we perform only five replicates, our standard errors or standard deviations may be larger than if we use ten replicates.

Larger standard errors reduce confidence in the results and we cannot as easily conclude that they are meaningful or significant. Now imagine that of these fertilization experiments were reported in the literature: 90 with an insufficient number of replicates perhaps 5 , and 10 with sufficient numbers of replicates 10 or more. If we summarized the literature by reviewing it, we would say 90 studies failed to find a significant effect of fertilizer on plants, and 10 found a significant effect—even though these results were purely a reflection of sample size.

Modified from Bigger and Marvier, The few studies with high statistical power that do demonstrate the phenomenon will be outweighed by the majority of experiments with low statistical power that fail to show it. One technique for detecting the true strength of replicated experiments is meta-analysis, a method for combining the results from different experiments that weights the studies based primarily on their sample size.

The method was pioneered in ecology by Jessica Gurrevitch and colleagues In meta-analysis the data are not re-analyzed, but rather the results from a number of different studies are examined to see whether together they demonstrate an effect that is significant. The individual effect sizes are weighted by the number of replicates performed for each experiment. An experiment with only a few replicates of a treatment would not be weighted as heavily as an experiment with 10 or 20 replicates.

As well as the effect sizes, some measure of the variation in experimental results is noted by drawing bars around the mean called confidence intervals. This is analogous to using error bars to represent the standard deviation. If these bars do not overlap each other on different treatments or between treatment and control, then statistically the differences are probably significant.

Effect size is measured as the log response ratio. Each point is the mean of a large number of studies. From Hawkes and Sullivan, If the bars overlap the zero value on the y-axis then the effect probably is not significant. Metaanalysis is being incorporated more frequently into ecology, and many different meta-analyses are mentioned in this book.

Some authors present the results of their meta-analyses data in terms of a different metric called the log response ratio, ln r. Thus, a negative value of this ratio suggests suppression by herbivores. The positive value of this ratio suggests increased growth by added resources.

In this case, added resources were light, water, or nutrients. In total, 81 records from 45 studies were included in the growth analysis and 24 records from 14 studies in the reproduction analysis. The advantage of this technique is that it estimates the effect as a proportional change resulting from experimental manipulations. In such cases, we might turn to the use of mathematical models. Suppose we thought that disease was causing the demise of an endangered species such as a giant panda.

We could not in good conscience experimentally expose giant pandas to the disease to see whether it decreased the population size of pandas. Instead, we might try to mathematically model what would happen.