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When one species is more efficient at exploiting a shared, limiting resource, it may be able to exclude the other species (see Section 13.2). However, when environmental conditions vary through time, the competitive advantages may also change. As a result, no one species reaches sufficient density to displace its compe... | {
"Header 1": "13.7 Temporal Variation in the Environment Influences Competitive Interactions",
"token_count": 743,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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In many cases, competition between species involves multiple resources and competition for one resource often influences an organism's ability to access other resources. One such example is the practice of interspecific territoriality, where competition for space influences access to food and nesting sites (see Section... | {
"Header 1": "**13.8** Competition Occurs for Multiple Resources",
"token_count": 1114,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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As environmental conditions change, so do the relative competitive abilities of species. Shifts in competitive ability can result either from changes in the carrying capacities of species (values of *K;* see Quantifying Ecology 13.1) related to a changing resource base or from changes in the physical environment that i... | {
"Header 1": "13.9 Relative Competitive Abilities Change along Environmental Gradients",
"token_count": 476,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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*Q1. Which of the three species of thistle included in the graph had the highest biomass production under the 1/64 nutrient treatment? What does this imply about this species' competitive ability under low nutrient availability relative to other thistle species?*
*Q2. Using relative biomass production at each treatme... | {
"Header 1": "13.9 Relative Competitive Abilities Change along Environmental Gradients",
"Header 3": "*Interpreting Ecological Data*",
"token_count": 1707,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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nder any set of environmental conditions, the outcome of interspecific competition reflects the relative abilities of the species involved to gain access and acquire the essential resources required for survival, growth, and reproduction. As we have seen in the analysis of interspecific competition using the Lotka-Volt... | {
"Header 1": "13.9 Relative Competitive Abilities Change along Environmental Gradients",
"Header 3": "Competition under Changing Environmental Conditions: Application of the Lotka–Volterra Model",
"token_count": 1253,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Previously, we defined the ecological niche of a species as the range of physical and chemical conditions under which it can persist (survive and reproduce) and the array of essential resources it uses and drew the distinction between the concepts of fundamental and realized niche (Chapter 12, Section 12.6). The fundam... | {
"Header 1": "**13.10** Interspecific Competition Influences the Niche of a Species",
"token_count": 1299,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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All terrestrial plants require light, water, and essential nutrients such as nitrogen and phosphorus. Consequently, competition between various co-occurring species is common. The same is true for the variety of insect-feeding bird species inhabiting the canopy of a forest, large mammalian herbivores feeding
![](_pag... | {
"Header 1": "13.11 Coexistence of Species Often Involves Partitioning Available Resources",
"token_count": 2030,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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fortis* population also feed on these seeds; in fact, during the 1976–1977 drought, the survival of the population depended on this seed resource (see Section 5.6 for a discussion of natural selection in this population).
Initially, the population of *G. magnirostris* on Daphne Major was too small in relation to the ... | {
"Header 1": "13.11 Coexistence of Species Often Involves Partitioning Available Resources",
"token_count": 474,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Demonstrating interspecific competition in laboratory "bottles" or the greenhouse is one thing; demonstrating competition under natural conditions in the field is another. In the field, researchers (1) have little control over the environment, (2) have difficulty knowing whether the populations are at or below carrying... | {
"Header 1": "13.12 Competition Is a Complex Interaction Involving Biotic and Abiotic Factors",
"token_count": 367,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Before European settlement, two species of wild dog (genus *Canis*) were among the most abundant large carnivores occupying the North American continent. The gray wolf, *Canis lupus,* once ranged from the Atlantic to the Pacific coast and from Alaska to northern Mexico (Figure 13.18). It occurred in virtually all North... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Is Range Expansion of Coyote a Result of Competitive Release from Wolves?",
"token_count": 1948,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Although data are limited to the few regions in which wolf populations have been successfully introduced, when combined with the results of studies of wolf–coyote interactions and population studies for regions of North America where these two species naturally co-occur (regions of Minnesota and Canada), a consistent... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Is Range Expansion of Coyote a Result of Competitive Release from Wolves?",
"token_count": 2056,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Provides a wealth of illustrated examples from laboratory, greenhouse, and field experiments.
environmental conditions change in time and space.
- Gurevitch, J. L., L. Murrow, A. Wallace, and J. J. Walch. 1992. "Meta-analysis of competition in field experiments." *American Naturalist* 140:539–572. An update of the ... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Is Range Expansion of Coyote a Result of Competitive Release from Wolves?",
"token_count": 246,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 14.1 Predation Takes a Variety of Forms
- 14.2 Mathematical Model Describes the Interaction of Predator and Prey Populations
- 14.3 Predator–Prey Interaction Results in Population Cycles
- 14.4 Model Suggests Mutual Population Regulation
- 14.5 Functional Responses Relate Prey Consumed to Prey Density
- 14.6 Predator... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "CHAPTER GUIDE",
"token_count": 464,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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The broad definition of predation as the consumption of one living organism (the prey) by another (the predator) excludes scavengers and decomposers. Nevertheless, this definition results in the potential classification of a wide variety of organisms as predators. The simplest classification of predators is represented... | {
"Header 1": "**14.1** Predation Takes a Variety of Forms",
"token_count": 759,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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In the 1920s, Alfred Lotka and Vittora Volterra turned their attention from competition (see Section 13.2) to the effects of predation on population growth. Independently, they proposed mathematical statements to express the relationship between predator and prey populations. They provided one equation for the prey pop... | {
"Header 1": "14.2 Mathematical Model Describes the Interaction of Predator and Prey Populations",
"token_count": 2030,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
(c) The combined zero isoclines provide a means of examining the combined population trajectories of the predator and prey populations. The black arrows represent the combined population trajectory. A minus sign indicates population decline, and a plus sign indicates population increase. This trajectory shows the cycli... | {
"Header 1": "14.2 Mathematical Model Describes the Interaction of Predator and Prey Populations",
"token_count": 881,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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The graphical analysis of the combined dynamics of the predator ( $N_{\text{pred}}$ ) and prey ( $N_{\text{prey}}$ ) populations using the zero-growth isoclines presented in Figure 14.2c reveal a cyclical pattern
that represents the changes in the two populations through time (Figure 14.3a). If we plot the changes in... | {
"Header 1": "14.3 Predator–Prey Interaction Results in Population Cycles",
"token_count": 1254,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The Lotka–Volterra model of predator–prey interactions assumes a mutual regulation of predator and prey populations. In the equations presented previously, the link between the growth of predator and prey populations is described by a single term relating to the consumption of prey: (*cN*prey)*N*pred. For the prey popu... | {
"Header 1": "14.4 Model Suggests Mutual Population Regulation",
"token_count": 739,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The English entomologist M. E. Solomon introduced the idea of functional response in 1949. A decade later, the ecologist C. S. Holling explored the concept in more detail, developing a simple classification based on three general types of functional response (Figure 14.6). The functional response is the relationship be... | {
"Header 1": "14.5 Functional Responses Relate Prey Consumed to Prey Density",
"token_count": 1404,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
he Type I functional response suggests a form of predation in which all of the time allocated to feeding is spent searching ( $T_{\rm s}$ ). In general, however, the time available for searching is shorter than the total time associated with consuming the $N_{\rm e}$ prey because time is required to "handle" the prey... | {
"Header 1": "14.5 Functional Responses Relate Prey Consumed to Prey Density",
"Header 3": "QUANTIFYING ECOLOGY 14.1 Type II Functional Response",
"token_count": 1922,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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As the density of prey increases, the predator population growth rate is expected to respond positively. A numerical response of predators can occur through reproduction by predators (as suggested by the conversion factor *b* in the Lotka–Volterra equation for predators) or through the movement of predators into areas ... | {
"Header 1": "14.6 Predators Respond Numerically to Changing Prey Density",
"token_count": 1859,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Thus far, we have discussed the activities of predators almost exclusively in terms of foraging. But all organisms are required to undertake a wide variety of activities associated with survival, growth, and reproduction. Time spent foraging must be balanced against other time constraints such as defense, avoiding pred... | {
"Header 1": "14.7 Foraging Involves Decisions about the Allocation of Time and Energy",
"token_count": 991,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
aced with a variety of potential food choices, predators make decisions regarding which types of food to eat and where and how long to search for food. But how are these decisions made? Do predators function opportunistically, pursuing prey as they are encountered, or do they make choices and pass by potential prey of ... | {
"Header 1": "14.7 Foraging Involves Decisions about the Allocation of Time and Energy",
"Header 3": "QUANTIFYING ECOLOGY 14.2 A Simple Model of Optimal Foraging",
"token_count": 1394,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Most predators are also prey to other predatory species and therefore face the risk of predation while involved in their routine activities, such as foraging. Habitats and foraging areas vary in their foraging profitability and their risk of predation. In deciding whether to feed, the forager must balance its potential... | {
"Header 1": "14.8 Risk of Predation Can Influence Foraging Behavior",
"token_count": 1162,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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By acting as agents of mortality, predators exert a selective pressure on prey species (see Chapter 12, Section 12.3). That is, any characteristic that enables individual prey to avoid being detected and captured by a predator increases its fitness. Natural selection functions to produce "smarter," more evasive prey (f... | {
"Header 1": "14.9 Coevolution Can Occur between Predator and Prey",
"token_count": 298,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Animal species have evolved a wide range of characteristics to avoid being detected, selected, and captured by predators. These characteristics are collectively referred to as **predator defenses**.
**Chemical defense** is widespread among many groups of animals. Some species of fish release alarm pheromones (chemica... | {
"Header 1": "14.10 Animal Prey Have Evolved Defenses against Predators",
"token_count": 2031,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As prey have evolved ways of avoiding predators, predators have evolved better ways of hunting. Predators use three general methods of hunting: ambush, stalking, and pursuit. Ambush hunting means lying in wait for prey to come along. This method is typical of some frogs, alligators, crocodiles, lizards, and certain ins... | {
"Header 1": "14.11 Predators Have Evolved Efficient Hunting Tactics",
"token_count": 529,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Although the term *predator* is typically associated with animals that feed on other animals, herbivory is a form of predation in which animals prey on autotrophs (plants and algae). Herbivory is a special type of predation because herbivores typically do not kill the individuals they feed on. Because the ultimate sour... | {
"Header 1": "14.12 Herbivores Prey on Autotrophs",
"token_count": 2035,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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These results clearly show that predator-induced shifts in traits early in development can subsequently alter traits later in development.
#### Bibliography
Relyea, R. 2001. "The lasting effects of adaptive plasticity: Predator-induced tadpoles become long-legged frogs." *Ecology* 82:1947–1955.
Relyea, R. 2002a. ... | {
"Header 1": "14.12 Herbivores Prey on Autotrophs",
"token_count": 917,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Most plants are sessile; they cannot move. Thus, avoiding predation requires adaptations that discourage being selected by herbivores. The array of characteristics used by plants to deter herbivores includes both structural and other defenses. Structural defenses, such as hairy leaves, thorns, and spines, can discourag... | {
"Header 1": "14.13 Plants Have Evolved Characteristics that Deter Herbivores",
"token_count": 1315,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In our discussion thus far, we have considered herbivory on plants and carnivory on animals as two separate topics, linked only by the common theme of predation. However, they are linked in another important way. Plants are consumed by herbivores, which in turn are consumed by carnivores. Therefore, we cannot really un... | {
"Header 1": "14.14 Plants, Herbivores, and Carnivores Interact",
"token_count": 579,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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The ability of predators to suppress prey populations has been well documented. Predators can suppress prey populations through consumption; that is, they reduce prey population growth by killing and eating individuals. Besides causing mortality, however, predators can cause changes in prey characteristics by inducing ... | {
"Header 1": "14.15 Predators Influence Prey Dynamics through Lethal and Nonlethal Effects",
"token_count": 1337,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Although the advent of agriculture some 10000 years ago reduced human dependence on natural populations of plants and animals as a food source, more than 80 percent of the world's commercial catches of fish and shellfish is from the harvest of naturally occurring populations in the oceans (71 percent) and inland freshw... | {
"Header 1": "ECOLOGICAL Issues & Applications",
"Header 3": "Sustainable Harvest of Natural Populations Requires Being a \"Smart Predator\"",
"token_count": 2034,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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The presence of abandoned fish processing plants and rusting fishing fleets support this view. With conservative, sustainable exploitation, the resource can be maintained.
#### Summary
#### Forms of Predation 14.1
Predation is defined generally as the consumption of all or part of one living organism by another. ... | {
"Header 1": "ECOLOGICAL Issues & Applications",
"Header 3": "Sustainable Harvest of Natural Populations Requires Being a \"Smart Predator\"",
"token_count": 2033,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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*Large herbivore ecology, ecosystem dynamics, and conservation.* New York: Cambridge University Press. Excellent synthesis of the impact of large herbivores on plant community structure and long-term plant diversity.
- Hay, M. E. 1991. "Marine-terrestrial contrasts in the ecology of plant chemical defenses against herb... | {
"Header 1": "ECOLOGICAL Issues & Applications",
"Header 3": "Sustainable Harvest of Natural Populations Requires Being a \"Smart Predator\"",
"token_count": 578,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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- 15.1 Parasites Draw Resources from Host Organisms
- 15.2 Hosts Provide Diverse Habitats for Parasites
- 15.3 Direct Transmission Can Occur between Host Organisms
- 15.4 Transmission between Hosts Can Involve an Intermediate Vector
- 15.5 Transmission Can Involve Multiple Hosts and Stages
- 15.6 Hosts Respond to Paras... | {
"Header 1": "ECOLOGICAL Issues & Applications",
"Header 3": "CHAPTER GUIDE",
"token_count": 620,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Parasitism is a type of symbiotic relationship between organisms of different species. One species—the parasite—benefits from a prolonged, close association with the other species—the host—which is harmed. Parasites increase their fitness by exploiting host organisms for food, habitat, and dispersal. Although they draw... | {
"Header 1": "**15.1** Parasites Draw Resources from Host Organisms",
"token_count": 1074,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Hosts are the habitats of parasites, and the diverse arrays of parasites that have evolved exploit every conceivable habitat on and within their hosts. Parasites that live on the host's skin, within the protective cover of feathers and hair, are **ectoparasites**. Others, known as **endoparasites**, live within the hos... | {
"Header 1": "15.2 Hosts Provide Diverse Habitats for Parasites",
"token_count": 479,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Direct transmission occurs when a parasite is transferred from one host to another without the involvement of an intermediate organism. The transmission can occur by direct contact with a carrier, or the parasite can be dispersed from one host to another through the air, water, or other substrate. Microparasites are mo... | {
"Header 1": "15.3 Direct Transmission Can Occur between Host Organisms",
"token_count": 514,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Some parasites are transmitted between hosts by an intermediate organism, or vector. For example, the black-legged tick (*Ixodes scapularis*) functions as an arthropod vector in the transmission of Lyme disease, which is the major arthropodborne disease in the United States. Named for its first noted occurrence at Lyme... | {
"Header 1": "15.4 Transmission between Hosts Can Involve an Intermediate Vector",
"token_count": 589,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Previously, we introduced the concept of life cycle—the phases associated with the development of an organism, typically divided into juvenile (or prereproductive), reproductive, and postreproductive phases (Chapter 10). Some species of parasites cannot complete their entire life cycle in a single host species. The hos... | {
"Header 1": "15.5 Transmission Can Involve Multiple Hosts and Stages",
"token_count": 398,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Just as the coevolution of predators and prey has resulted in the adaptation of defense mechanisms by prey species, host species likewise exhibit a range of adaptations that minimize the impact of parasites. Some responses are mechanisms that reduce parasitic invasion. Other defense mechanisms aim to combat parasitic i... | {
"Header 1": "15.6 Hosts Respond to Parasitic Invasions",
"token_count": 1042,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Although host organisms exhibit a wide variety of defense mechanisms to prevent, reduce, or combat parasitic infection, all share the common feature of requiring resources that the host might otherwise have used for some other function. Given that organisms have a limited amount of energy, it is not surprising that par... | {
"Header 1": "15.7 Parasites Can Affect Host Survival and Reproduction",
"token_count": 821,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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For parasite and host to coexist under a relationship that is hardly benign, the host needs to resist invasion by eliminating the parasites or at least minimizing their effects. In most circumstances, natural selection has resulted in a level of immune response in which the allocation of metabolic resources by the host... | {
"Header 1": "15.8 Parasites May Regulate Host Populations",
"token_count": 1426,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Parasites and their hosts live together in a symbiotic relationships in which the parasite derives its benefit (habitat and food resources) at the expense of the host organism. Host species have evolved a variety of defenses to minimize the negative impact of the parasite's presence. In a situation in which adaptations... | {
"Header 1": "15.9 Parasitism Can Evolve into a Mutually Beneficial Relationship",
"token_count": 691,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Mutualistic relationships involve many diverse interactions that extend beyond simply acquiring essential resources. Thus, it is important to consider the different attributes of mutualistic relationships and how they affect the dynamics of the populations involved. Mutualisms can be characterized by a number of variab... | {
"Header 1": "15.10 Mutualisms Involve Diverse Species Interactions",
"token_count": 1036,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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The digestive system of herbivores is inhabited by a diverse community of mutualistic organisms that play a crucial role in the digestion of plant materials. The chambers of a ruminant's stomach contain large populations of bacteria and protists that carry out the process of fermentation (see Section 7.2). Inhabitants ... | {
"Header 1": "15.11 Mutualisms Are Involved in the Transfer of Nutrients",
"token_count": 2050,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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protein, a building block of all living material. Although nitrogen is the most abundant constituent of the atmosphere approximately 79 percent in its gaseous state—it is unavailable to most life. It must first be converted into a chemically usable form. One group of organisms that can use gaseous nitrogen (N2) is th... | {
"Header 1": "15.11 Mutualisms Are Involved in the Transfer of Nutrients",
"token_count": 640,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Other mutualistic associations involve defense of the host organism. A major problem for many livestock producers is the toxic effects of certain grasses, particularly perennial ryegrass and tall fescue. These grasses are infected by symbiotic endophytic fungi that live inside plant tissues. The fungi (Clavicipitaceae ... | {
"Header 1": "15.12 Some Mutualisms Are Defensive",
"token_count": 709,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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The goal of cross-pollination is to transfer pollen from the anthers of one plant to the stigma of another plant of the same species (see Figure 12.3). Some plants simply release their pollen in the wind. This method works well and costs little when plants grow in large homogeneous stands, such as grasses and
![](_pa... | {
"Header 1": "15.13 Mutualisms Are Often Necessary for Pollination",
"token_count": 603,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Plants with seeds too heavy to be dispersed by wind depend on animals to carry them some distance from the parent plant and deposit them in sites favorable for germination and seedling establishment. Some seed-dispersing animals on which the plants depend may be seed predators as well, eating the seeds for their own nu... | {
"Header 1": "15.14 Mutualisms Are Involved in Seed Dispersal",
"token_count": 1108,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Mutualism is easy to appreciate at the individual level. We grasp the interaction between an ectomycorrhizal fungus and its oak or pine host, we count the acorns dispersed by squirrels and jays, and we measure the cost of dispersal to oaks in terms of seeds consumed. Mutualism improves the growth and reproduction of th... | {
"Header 1": "15.15 Mutualism Can Influence Population Dynamics",
"token_count": 1925,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The cutting and clearing of forests to allow for the expansion of agriculture and urbanization has long been associated with declining plant and animal populations and the reduction of biological diversity resulting from habitat loss (see Chapters 9 and 12, *Ecological Issues & Applications*); however, recent research ... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Land-use Changes Are Resulting in an Expansion of Infectious Diseases Impacting Human Health",
"token_count": 2036,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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They are small, have a short generation time, multiply rapidly in the host, tend to produce immunity, and spread by direct transmission. They are usually associated with dense populations of hosts. Macroparasites are relatively large and include parasitic worms, lice, ticks, fleas, rusts, smuts, fungi, and other forms.... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Land-use Changes Are Resulting in an Expansion of Infectious Diseases Impacting Human Health",
"token_count": 1077,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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- **1.** If a parasite's life cycle involves multiple hosts, what might control the population dynamics of the parasite? How do birds and mammals avoid parasitic infection through their behavior?
- **2.** For the parasite trematode discussed in Section 15.7, infection begins as snails grazing on algae incidentally inge... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "S tudy Q uesti o ns",
"token_count": 383,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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#### Classic Studies
- Boucher, D. H., ed. 1988. *The biology of mutualism*. New York, Oxford University Press.
- This volume provides a multitude of examples describing the range of mutualistic relationships covered in this chapter.
- Futuyma, D. J., and M. Slatkin, eds. 1983. *Coevolution.* Sunderland, MA: Sinauer ... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "F urther Readings",
"token_count": 1385,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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The biological structure of a community is defined by its species composition, that is, the set of species present and their relative abundances. For example, **Table 16.1** contains samples representing tree species composition of two forest communities in northern West Virginia. For each forest, the first column prov... | {
"Header 1": "16.1 Biological Structure of Community Defined by Species Composition",
"token_count": 1930,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Although the graphical procedure of rank-abundance diagrams can be used to visually assess (interpret) differences in the biological structure of communities, these diagrams offer no means of quantifying the observed differences. The simplest quantitative measure of community structure is the index of species richness ... | {
"Header 1": "16.2 Species Diversity Is Defined by Species Richness and Evenness",
"token_count": 1304,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Although the numbers of tree species occurring in the two forest communities (species richness) presented in Tables 16.1 differ more than twofold, the two communities share a common feature. Both communities are composed of a few common tree species with high population density, whereas the remaining tree species are r... | {
"Header 1": "16.3 Dominance Can Be Defined by a Number of Criteria",
"token_count": 1255,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Relative abundance is just one measure, based only on numerical supremacy, of a species' contribution to the community. Other, less-abundant species, however, may play a crucial role in the function of the community. A species that has a disproportionate impact on the community relative to its abundance is referred to ... | {
"Header 1": "16.4 Keystone Species Influence Community Structure Disproportionately to Their Numbers",
"token_count": 1244,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Perhaps the most fundamental process in nature is that of acquiring the energy and nutrients required for assimilation. The species interactions discussed earlier—predation, parasitism, competition, and mutualism—are all involved in acquiring these essential resources (Part Four). For this reason, ecologists studying t... | {
"Header 1": "16.5 Food Webs Describe Species Interactions",
"token_count": 2024,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
An analysis of the mechanisms controlling community structure must include these "indirect" effects represented by the structure of the food web; we will explore this topic in more detail later (Chapter 17).
The simple designation of feeding relationships using the graphical approach of food webs can become incredibl... | {
"Header 1": "16.5 Food Webs Describe Species Interactions",
"token_count": 203,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The grouping of species into trophic levels is a functional classification; it defines groups of species that derive their energy (food) in a similar manner. Another approach is to subdivide each trophic level into groups of species that exploit a common resource in a similar fashion; these groups are termed **guilds**... | {
"Header 1": "16.6 Species within a Community Can Be Classified into Functional Groups",
"token_count": 576,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Communities are characterized not only by the mix of species and by the interactions among them—their biological structure but also by their physical features. The physical structure of the community reflects abiotic factors, such as the depth and flow of water in aquatic environments. It also reflects biotic factors, ... | {
"Header 1": "16.7 Communities Have a Characteristic Physical Structure",
"token_count": 1617,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
2013.)
**(b)**
| | | | Relative abundance<br>(% Total number of individuals) | | |
|----------------------------------------------------------------|-------------------------------------... | {
"Header 1": "16.7 Communities Have a Characteristic Physical Structure",
"token_count": 919,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As we move across the landscape, the biological and physical structure of the community changes. Often these changes are small, subtle ones in the species composition or height of the vegetation. However, as we travel farther, these changes often become more pronounced. For example, in a study of the vegetation of the ... | {
"Header 1": "16.8 Zonation Is Spatial Change in Community Structure",
"token_count": 1121,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As previously noted, the community is a spatial concept involving the species that occupy a given area. Ecologists typically distinguish between adjacent communities or community types based on observable differences in their physical and biological structures: the different species assemblages characteristic of differ... | {
"Header 1": "16.9 Defining Boundaries between Communities Is Often Difficult",
"token_count": 663,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
When we say that a community's structure changes as we move across the landscape, we imply that the set of species that define the community differ from one place to another. But how do we quantify this change? How do ecologists determine where one community ends and another begins? Distinguishing between communities b... | {
"Header 1": "16.9 Defining Boundaries between Communities Is Often Difficult",
"Header 3": "QUANTIFYING ECOLOGY 16.1 Community Similarity",
"token_count": 891,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
At the beginning of this chapter, we defined the community as the group of species (populations) that occupy a given area, interacting either directly or indirectly. Interactions can have both positive and negative influences on species populations. How important are these interactions in determining community structur... | {
"Header 1": "16.10 Two Contrasting Views of the Community",
"token_count": 1021,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As we have discussed in previous chapters, human activities have led to population declines and even extinction of a growing number of plant and animal species. Landuse changes associated with the expansion of agriculture (Chapter 9, *Ecological Issues & Applications*) and urbanization (Chapter 12, *Ecological Issues &... | {
"Header 1": "Restoration Ecology Requires an Understanding of the Processes Influencing the Structure and Dynamics of Communities",
"token_count": 2021,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Within a community, many food chains mesh into a complex food web with links leading from primary producers to an array of consumers. Species that are fed on but that do not feed on others are termed *basal species*. Species that feed on others but are not prey for other species are termed *top predators*. Species that... | {
"Header 1": "Restoration Ecology Requires an Understanding of the Processes Influencing the Structure and Dynamics of Communities",
"token_count": 1338,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 17.1 Community Structure Is an Expression of the Species' Ecological Niche
- 17.2 Zonation Is a Result of Differences in Species' Tolerance and Interactions along Environmental Gradients
- 17.3 Species Interactions Are Often Diffuse
- 17.4 Food Webs Illustrate Indirect Interactions
- 17.5 Food Webs Suggest Controls o... | {
"Header 1": "CHAPTER GUIDE",
"token_count": 358,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As we discussed in Chapter 16, the biological structure of a community is defined by its species composition, that is, the species present and their relative abundances. For a species to be a component of an ecological community at a given location, it must first and foremost be able to survive. The environmental condi... | {
"Header 1": "17.1 Community Structure Is an Expression of the Species' Ecological Niche",
"token_count": 1438,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
We have now seen that the biological structure of a community is first constrained by the species' environmental tolerances its fundamental niche. In turn, the fundamental niche is modified through interactions with other species (realized niche). Competitors and predators, for example, can restrict a species from a co... | {
"Header 1": "17.2 Zonation Is a Result of Differences in Species' Tolerance and Interactions along Environmental Gradients",
"token_count": 504,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Department of Zoology, Oregon State University, Corvallis, Oregon
alt marsh plant communities are ideal for examining the forces that structure natural communities. They are typically dominated by a small number of plant species that form distinct zonation patterns (see Figure 16.16). Seaward distribution of marsh pl... | {
"Header 1": "17.2 Zonation Is a Result of Differences in Species' Tolerance and Interactions along Environmental Gradients",
"Header 3": "FIELD STUDIES Sally D. Hacker",
"token_count": 2008,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
How does the presence of *Juncus* function to maintain the aphid populations in the marsh?
on community structure, the ecologist Joseph Connell of the University of California–Santa Barbara, performed a series of now-classic experiments on these two species of barnacles at a site along the Scottish coast. Connell est... | {
"Header 1": "17.2 Zonation Is a Result of Differences in Species' Tolerance and Interactions along Environmental Gradients",
"Header 3": "FIELD STUDIES Sally D. Hacker",
"token_count": 1745,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Soil moisture gradient
Figure 17.5 General trends in plant adaptations (characteristics) that increase fitness along a soil moisture gradient. For species adapted to low soil moisture (dry adapted), allocation to the production of roots at the expense of leaves aids in acquiring water and reducing transpiration, allo... | {
"Header 1": "Dry **Dry-adapted** High allocation to roots Low allocation to leaves and stems Low maximum growth rate High tolerance to water stress Low allocation to roots High allocation to leaves and stems High maximum growth rate Low tolerance to water stress Wet Higher maximum growth of wet-adapted species resu... |
As we have seen in the previous chapters and sections, most studies that examine the role of species interactions on community structure typically focus on the direct interaction between two, or at best, a small subset of the species found within a community. As a result, such studies most likely underestimate the impo... | {
"Header 1": "17.3 Species Interactions Are Often Diffuse",
"token_count": 1011,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Food webs also illustrate a second important feature of species interactions within the community: indirect effects. Indirect interactions occur when one species does not interact with a second species directly but instead influences a third species that does directly interact with the second. For example, in the food ... | {
"Header 1": "17.4 Food Webs Illustrate Indirect Interactions",
"token_count": 2011,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The indirect interaction between the midge and the larval salamander is referred to as **indirect commensalism** because the interaction is beneficial to the midge but neutral to the larval salamander. When the indirect interaction is beneficial to both species, the indirect interaction is termed **indirect mutualism**... | {
"Header 1": "17.4 Food Webs Illustrate Indirect Interactions",
"token_count": 527,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The wealth of experimental evidence illustrates the importance of both direct and indirect interactions on community structure. On that basis, rejecting the null model as presented in Section 17.1 would be justified. However, given the complexity of direct and indirect interactions suggested by food webs, how can we be... | {
"Header 1": "17.5 Food Webs Suggest Controls of Community Structure",
"token_count": 1561,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As we have seen thus far, the biological structure (species composition) of a community reflects both the direct response (survival, growth, and reproduction) of the component species to the prevailing abiotic environmental conditions, as well as their interactions (direct and indirect). In turn, as environmental condi... | {
"Header 1": "17.6 Environmental Heterogeneity Influences Community Diversity",
"token_count": 1391,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
We examined the role of nutrient availability on plant processes (see Section 6.11). In general, increased availability of nutrients can support higher rates of photosynthesis, plant growth, and a higher density of plants per unit area. It might seem somewhat odd, therefore, that a variety of studies have shown an inve... | {
"Header 1": "17.7 Resource Availability Can Influence Plant Diversity within a Community",
"token_count": 2044,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
A trophic cascade occurs when predators suppress the population of their prey (herbivores), thereby releasing the next lower trophic level (autotrophs) from predation (Section 17.5, Figure 17.15). One of the most dramatic and well-documented examples of a trophic cascade is the recovery of vegetation in regions of the ... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "The Reintroduction of a Top Predator to Yellowstone National Park Led to a Complex Trophic Cascade",
"token_count": 2043,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In diffuse competition, direct interaction between any two species may be weak, making it difficult to determine the effect of any given species on another. Collectively, however, competition may be an important factor limiting the abundance of all species involved. Diffuse interactions involving predation and competit... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "The Reintroduction of a Top Predator to Yellowstone National Park Led to a Complex Trophic Cascade",
"token_count": 1054,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
#### Classic Studies
- Connell, J. 1961. "The influence of interspecific competition and other factors on the distribution of the barnacle *Chthamalus stellatus*." *Ecology* 42:710–723. This article presents one of the early field experiments examining the role of interspecific competition in patterns of community zo... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "F urther Readings",
"token_count": 821,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 18.1 Community Structure Changes through Time
- 18.2 Primary Succession Occurs on Newly Exposed Substrates
- 18.3 Secondary Succession Occurs after Disturbances
- 18.4 The Study of Succession Has a Rich History
- 18.5 Succession Is Associated with Autogenic Changes in Environmental Conditions
- 18.6 Species Diversity... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Chapter Guide",
"token_count": 336,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Community structure varies in time as well as in space. Suppose that rather than moving across the landscape, as with the examples of zonation presented earlier (see Section 16.8, Figures 16.15–16.19), we stand in one position and observe the area as time passes. For example, abandoned cropland and pastureland are comm... | {
"Header 1": "**18.1** Community Structure Changes through Time",
"token_count": 1630,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Primary succession begins on sites that have never supported a community, such as rock outcrops and cliffs, lava fields, sand dunes, and newly exposed glacial till. For example, consider primary succession on an inhospitable site: a sand dune. Sand, a product of weathered rock, is deposited by wind and water. Where dep... | {
"Header 1": "18.2 Primary Succession Occurs on Newly Exposed Substrates",
"token_count": 1028,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
A classic example of secondary succession in terrestrial environments is the study of old-field succession in the Piedmont region of North Carolina by the eminent plant ecologist Dwight Billings (Duke University) in the late 1930s (see Figure 18.1). During the first year after a crop field has been abandoned, the groun... | {
"Header 1": "18.3 Secondary Succession Occurs after Disturbances",
"token_count": 1572,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The study of succession has been a focus of ecological research for more than a century. Early in the 20th century, botanists E. Warming in Denmark and Henry Cowles in the United States largely developed the concept of ecological succession. The intervening years have seen a variety of hypotheses attempting to address ... | {
"Header 1": "**18.4** The Study of Succession Has a Rich History",
"token_count": 2041,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Note the AL + AS + AR = 1. Each diagonal line is an equal allocation to roots. The allocation patterns of five species (A–E) are shown. These allocation patterns reflect a shift in plant strategies from adaptation to low nutrient and high light (species A) levels, to adaptation to high nutrient and low light (species E... | {
"Header 1": "**18.4** The Study of Succession Has a Rich History",
"token_count": 225,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The changes in environmental conditions that bring about shifts in the physical and biological structures of communities across the landscape are varied. They can, however, be grouped into two general classes: autogenic and allogenic. Autogenic environmental change is a direct result of the presence and activities of o... | {
"Header 1": "18.5 Succession Is Associated with Autogenic Changes in Environmental Conditions",
"token_count": 2026,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In addition to shifts in species dominance, patterns of plant species diversity change over the course of succession. Studies of secondary succession in old-field communities have shown that plant species diversity typically increases with site age (that is, time since abandonment). The late plant ecologist Robert Whit... | {
"Header 1": "18.6 Species Diversity Changes during Succession",
"token_count": 1089,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Although our discussion and examples of succession have thus far focused on temporal changes in the autotrophic component of the community (plant succession), associated changes in the heterotrophic component also occur. As plant succession advances, changes in the structure and composition of the vegetation result in ... | {
"Header 1": "**18.7** Succession Involves Heterotrophic Species",
"token_count": 1653,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The focus on succession thus far has been on shifting patterns of community structure in response to autogenic changes in environmental conditions. Such changes occur at timescales relating to the establishment and growth of the organisms that make up the community. However, purely abiotic environmental (allogenic) cha... | {
"Header 1": "18.8 Systematic Changes in Community Structure Are a Result of Allogenic Environmental Change at a Variety of Timescales",
"token_count": 743,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Since its inception some 4.6 billion years ago, Earth has changed profoundly. Landmasses emerged and broke into continents. Mountains formed and eroded, seas rose and fell, and ice sheets advanced to cover large expanses of the Northern and Southern Hemispheres and then retreated. All these changes affected the climate... | {
"Header 1": "18.9 Community Structure Changes over Geologic Time",
"token_count": 780,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Our initial discussion of the processes influencing community structure and dynamics contrasted two views of the community (see Section 16.10). Through his organismal concept, Frederic Clements viewed the community as a quasi-organism made up of interdependent species. By contrast, in his individualistic or continuum c... | {
"Header 1": "18.10 The Concept of Community Revisited",
"token_count": 1347,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Old-field communities, such as the one shown in Figure 18.1, are a common sight in the eastern portion of the United States. These fields represent the early stages in the process of secondary succession, a process that began with the abandonment of agricultural lands (cropland or pasture) and that will eventually lead... | {
"Header 1": "ECOLOGICAL Issues & Applications",
"Header 3": "Community Dynamics in Eastern North America over the Past Two Centuries Are a Result of Changing Patterns of Land Use",
"token_count": 2047,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
#### Community Revisited 18.10
The community is a spatial concept; the individual continuum is a population concept. Each species has a continuous response to an environmental gradient, such as elevation or moisture. Yet the spatial distribution of that environmental variable across the landscape determines the ove... | {
"Header 1": "ECOLOGICAL Issues & Applications",
"Header 3": "Community Dynamics in Eastern North America over the Past Two Centuries Are a Result of Changing Patterns of Land Use",
"token_count": 1476,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
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