final

base level

level of a stream where down-cutting ceases

metapopulation

linear series of populations separated into discrete groups Species often exist as a network of distinct populations that exchange individuals. Such networks, termed metapopulations, usually occur in areas in which suitable habitat is patchily distributed and is separated by intervening stretches of unsuitable habitat.

substrate

an underlying substance or layer. the surface or material on or from which an organism lives, grows, or obtains its nourishment. "brachiopods attached to the substrate by a stalk" the substance on which an enzyme acts.

channel

area of stream occupied by water (high, normal and low flow)

pool

area where stream is not visible moving (often along the margins of streams)

run

area where stream is visibly moving, but surface is not broken

riffle

area where stream surface is broken

natality/mortality

birth rate - death rate

types of symbiotic interactions (neutralism, competition, parasitism, predation, commensalism, mutualism)

mutualism, in which both participating species benefit parasitism, in which one species benefits but the other is harmed commensalism, in which one species benefits and the other neither benefits nor is harmed. predation, one organism captures and consumes another neutralism, neither population effects the other. any interactions that do occur are indirect or accidental competition, organisms fight or compete for food, shelter, a mate, or other resources

headwaters

reach of stream farthest from the mouth (where down-cutting ceases)

riparian

relating to or situated on the banks of a river. relating to wetlands adjacent to rivers and streams.

saprotroph/decomposer

saprobes Heterotrophic organisms that digest their food externally an organism that feeds on or derives nourishment from decaying organic matter.

neuston

small aquatic organisms inhabiting the surface layer or moving on the surface film of water.

benthic

the bottom of a body of water.

depositional bank

where sediments are being accumulated

erosional bank

where sediments are being removed

gause's principle of competitive exclusion (Interspecific competition, Resource partitioning)

competitive exclusion The hypothesis that two species with identical ecological requirements cannot exist in the same locality indefinitely, and that the more efficient of the two in utilizing the available scarce resources will exclude the other; also known as Gause's principle. In classic experiments carried out in 1934 and 1935, Russian ecol- ogist Georgii Gause studied competition among three species of Paramecium, a tiny protist. Each of the three species grew well in culture tubes by themselves, preying on bacteria and yeasts that fed on oatmeal suspended in the culture fluid. However, when Gause grew P. aurelia together with P. caudatum in the same culture tube, the numbers of P. caudatum always declined to extinction, leaving P. aurelia the only survivor. Why did this happen? Gause found that P. aurelia could grow six times faster than its competitor P. caudatum because it was able to better utilize the limited available resources, an example of exploitative competition. From experiments such as this, Gause formulated what is now called the principle of competitive exclusion. This principle states that if two species are competing for a limited resource such as food or water, the species that uses the resource more efficiently will eventually eliminate the other locally. In other words, no two species with the same niche can coexist when resources are limiting. Sometimes species are not able to occupy their entire niche because of the presence or absence of other species. Species can interact with one another in a number of ways, and these interac- tions can either have positive or negative effects. One type of inter- action, interspecific competition, occurs when two species use the same resource and there is not enough to satisfy both. Physical interactions over access to resources—such as fighting to defend a territory or displacing an individual from a particular location— are referred to as interference competition; consuming the same resources is called exploitative competition.

omnivore

eat both primary producers and other animals

side cutting

erosion of the stream banks

down cutting

erosion of the stream bed (also called bed load)

limiting factors

for all organisms, abundance and distribution are limited by their environment:

wetland

Freshwater wetlands—marshes, swamps, and bogs—represent intermediate habitats between the freshwater and terrestrial realms. Wetlands are highly productive (see figure 57.11). They also play key additional roles, such as acting as water storage basins that moderate flooding.

gaseous cycle: fast, controlled by organisms, eg nitrogen

Nitrogen

k = carrying capacity

No matter how rapidly populations grow, they eventually reach a limit imposed by shortages of important environmental factors, such as space, light, water, or nutrients. A population ultimately may sta- bilize at a certain size, called the carrying capacity of the particular place where it lives. The carrying capacity, symbolized by K, is the maximum number of individuals that the environment can support.

Ecosystem

"Any unit that includes all of the organisms in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles within the system is an ecological system or ecosystem."

ecological communities

Ecological communities are comprised of all the populations within an ecosystem. Organisms interact with each other in ecosystems to form these communities. Just like species and populations, communities have characteristics that are predictable.

Carbon cycle

5 trillion tons in earths crustup to 1 trillion tons in organisms 0.7 trillion tons in atmosphere

open water habitats (nekton, plankton)

A nekton is a group of water or marine organisms that travel together freely. These organisms can be fish, crustaceans or mollusks that live in an ocean or a lake. They tend to move without the help of the current. Phytoplankton, also known as microalgae, are similar to terrestrial plants in that they contain chlorophyll and require sunlight in order to live and grow. Most phytoplankton are buoyant and float in the upper part of the ocean, where sunlight penetrates the water.

causes of species richness (ecosystem productivity, spatial heterogeneity, evolutionary age, predictability, predation/minor disturbance)

A number of factors are known or hypothesized to affect species richness in a community. Primary productivity Ecosystems differ substantially in primary productivity (see figure 57.11). Some evidence indicates that species richness is related to primary productivity, but the relationship between them is not linear. In a number of cases, for example, ecosystems with intermediate levels of productivity tend to have the greatest number of species (figure 57.20a). Why this is so is debated. One possibility is that levels of productivity are linked with numbers of consumers. Applying this concept to plant species richness, the argument is that at low pro- ductivity, there are few herbivores, and superior competitors among the plants are able to eliminate most other plant species. In contrast, at high productivity so many herbivores are present that only the plant species most resistant to grazing survive, reducing species diversity. As a result, the greatest numbers of plant species coexist at intermediate levels of productivity and herbivory. Habitat heterogeneity Spatially heterogeneous abiotic environments are those that con- sist of many habitat types—such as soil types, for example. These heterogeneous environments can be expected to accommodate more species of plants than spatially homogeneous environments. What's more, the species richness of animals can be expected to reflect the species richness of plants present. An example of this latter effect is seen in figure 57.20b: The number of lizard species at various sites in the American Southwest mirrors the local structural diversity of the plants. Climatic factors The role of climatic factors is more difficult to predict. On the one hand, more species might be expected to coexist in a seasonal en- vironment than in a constant one because a changing climate may favor different species at different times of the year. On the other hand, stable environments are able to support specialized species that would be unable to survive where conditions fluctuate. The number of mammal species at locations along the West Coast of North America is inversely correlated with the amount of local temperature variation—the wider the variation, the fewer mamma- lian species—supporting the latter line of argument

abiotic/biotic

Abiotic: nonliving component of an ecosystem Biotic: living component of an ecosystem

index of biotic integrity (IBI) (species composition metrics, trophic structure metrics, fish conditions metrics)

An Index of Biological Integrity (IBI) is a synthesis of diverse biological information which numerically depicts associations between human influence and biological attributes. It is composed of several biological attributes or 'metrics' that are sensitive to changes in biological integrity caused by human activities.

detritivore

An additional consumer level is the detritivore trophic level. Detritivores differ from the organisms in the other trophic levels in that they feed on the remains of already dead organisms; detritus is dead organic matter. A subcategory of detritivores is the decomposers, which are mostly microbes and other minute organ- isms that live on and break up dead organic matter.

autotroph

An organism able to build all the complex organic molecules that it requires as its own food source, using only simple inorganic compounds.

heterotroph

An organism that cannot derive energy from photosynthesis or inorganic chemicals, and so must feed on other plants and animals, obtaining chemical energy by degrading their organic molecules.

niche theory (hypervolume niche, theoretical/fundamental niche, realized niche)

Animals perform activities within an ecosystem - the myriad of activities an organism can play comprises it niche - often thought of as an organism's job in an ecosystem. Realized niche - the niche actually performed by the organism Theoretical niche - the potential niche of an organism (the job it could do) Hypervolume niche - the total number of variables available for niche specialization Niche and habitat are not the same

range: random, uniform, clumped

Another key characteristic of population structure is the way in which individuals of a population are distributed. They may be randomly spaced, uniformly spaced, or clumped. Random spacing of individuals within populations occurs when they do not interact strongly with one another and when they are not affected by nonuniform aspects of their environment. Random distributions are not common in nature. Some species of trees, however, appear to exhibit random distributions in Panamanian rainforests. Uniform spacing within a population may often, but not always, result from competition for resources. This spacing is accom- plished, however, in many different ways. In animals, uniform spacing often results from behavioral interactions, as described in chapter 54. In many species, indi- viduals of one or both sexes defend a territory from which other individuals are excluded. These territories provide the owner with exclusive access to resources, such as food, water, hiding refuges, or mates, and tend to space individuals evenly across the habitat. Even in nonterritorial species, individuals often maintain a defended space into which other animals are not allowed to intrude. Among plants, uniform spacing is also a common result of competition for resources. Closely spaced individual plants com- pete for available sunlight, nutrients, or water. These contests can be direct, as when one plant casts a shadow over another, or indi- rect, as when two plants compete by extracting nutrients or water from a shared area. In addition, some plants, such as the creosote bush, produce chemicals in the surrounding soil that are toxic to other members of their species. In all of these cases, only plants that are spaced an adequate distance from each other will be able to coexist, leading to uniform spacing. Individuals clump into groups or clusters in response to uneven distribution of resources in their immediate environments. Clumped distributions are common in nature because individual animals, plants, and microorganisms tend to occur in habitats de- fined by soil type, moisture, or other aspects of the environment to which they are best adapted. Social interactions also can lead to clumped distributions. Many species live and move around in large groups, which go by a variety of names (for example, flock, herd, pride). These group- ings can provide many advantages, including increased awareness of and defense against predators, decreased energy cost of moving through air and water, and access to the knowledge of all group members. On a broader scale, populations are often most densely pop- ulated in the interior of their range and less densely distributed to- ward the edges. Such patterns usually result from the manner in which the environment changes in different areas. Populations are often best adapted to the conditions in the interior of their distribu- tion. As environmental conditions change, individuals are less well adapted, and thus densities decrease. Ultimately, the point is reached at which individuals cannot persist at all; this marks the edge of a population's range.

succession (primary- barren rock succession. glacier bay, Alaska.) (pond succession) (secondary)

Change in community structure that is controlled by the community Primary succession: barren rock succession Secondary succession Seres are composed of linear or radial seral stages Pioneering species are usually r-selected r & K refer to the slope of the population growth curve and carrying capacity r-selected organisms are fast growing, reproduce young, produce a lot of young, and don't put much effort (care) into the young K-selected organisms are slow growing, reproduce at a later age, produce few young, and perform parental care Climax species are usually K-selected Pond succession An example of primary succession Composed of radial seral stages Open water -> emergent vegetation -> buttonbush swamp -> swamp forest -> upland forest Barren rock succession (Glacier Bay, Alaska) An example of primary succession Composed of a liner series of seres Barren rock -> mosses -> grasses -> herbs -> brush -> trees -> climax tree community Stream succession Water-willow succession Gravel bar -> water willow -> sandbar willow -> black willow/sycamore Tolerance leads to Facilitation, which leads to Inhibition Succession happens because species alter the habitat and the resources available in it in ways that favor other species. Three dynamic concepts are of critical importance in the process: estab- lishment, facilitation, and inhibition: 1. Establishment. Early successional stages are characterized by weedy, r-selected species that are tolerant of the harsh, abiotic conditions in barren areas (chapter 55 discussed r-selected and K-selected species). Facilitation. The weedy early successional stages introduce local changes in the habitat that favor other, less weedy species. Thus, the mosses in the Glacier Bay succession convert nitrogen to a form that allows alders to invade (figure 56.24). Similarly, the nitrogen build-up produced by the alders, though not necessary for spruce establishment, leads to more robust forests of spruce better able to resist attack by insects. Inhibition. Sometimes the changes in the habitat caused by one species, while favoring other species, also inhibit the growth of the original species that caused the changes. Alders, for example, do not grow as well in acidic soil as the spruce and hemlock that replace them. Over the course of succession, the number of species typi- cally increases as the environment becomes more hospitable. In some cases, however, as ecosystems mature, more K-selected species replace r-selected ones, and superior competitors force out other species, leading ultimately to a decline in species richness.

pond (emergent plant community, floating plant community, submergent plant community, algae)

Emergent plants live near the water's edge and along the banks of rivers. These vascular plants often have deep and dense roots that stabilize shallow soils at the water's edge. They also provide important habitat for birds, insects, and other animals living near water. Floating plants have leaves that float on the water surface. Their roots may be attached in the substrate or floating in the water column. Submersed macrophytes are also rooted to the bottom but their leaves grow entirely underwater.

types of indirect symbiotic relationships (food chain mutualism, exploitive competition/indirect competition)

Exploitation competition occurs when individuals interact indirectly as they compete for common resources, like territory, prey or food. Simply put, the use of the resource by one individual will decrease the amount available for other individuals.

resource partitioning

Gause's competitive exclusion principle has a very important consequence: If competition for a limited resource is intense, then either one species will drive the other to extinction, or the species will evolve differences that reduce the competition between them. When the ecologist Robert MacArthur studied five spe- cies of warblers, small insect-eating forest songbirds, he dis- covered that they appeared to be competing for the same resources. But when he investigated in greater detail he found that each species actually fed in a different part of spruce trees and so ate different subsets of insects. One species fed on insects near the tips of branches, a second within the dense foliage, a third on the lower branches, a fourth high on the trees, and a fifth at the very apex of the trees. Thus, each species of warbler had evolved so as to utilize a different portion of the spruce tree resource. They had subdivided the niche to avoid direct competition with one another. This niche subdivision is termed resource partitioning. Resource partitioning is often seen in similar species that occupy the same geographic area. Such sympatric species (that is, species that occur together) often avoid competition by living in different portions of the habitat or by using different food or other resources. This pattern of resource partitioning is thought to result from the process of natural selection causing initially similar species to diverge in resource use to reduce competi- tive pressures.

ecological pyramids (pyramid of energy, numbers, biomass)

In a pyramid of biomass, the widths of the boxes are drawn to be proportional to standing crop biomass. Usually, trophic levels that have relatively low productivity also have relatively little biomass present at a given time. Thus, pyramids of biomass are usually upright, meaning each box is narrower than the one below it (figure 57.13b). An upright pyramid of biomass is not mandated by fundamental and inviolable rules like an upright pyramid of productivity is, however. In some eco- systems, the pyramid of biomass is inverted, meaning that at least one trophic level has greater biomass than the one below it (figure 57.13c). How is it possible for the pyramid of biomass to be inverted? Consider a common sort of aquatic system in which the primary pro- ducers are single-celled algae (phytoplankton), and the herbivores are rice grain-sized animals (such as copepods) that feed directly on the algal cells. In such a system, the turnover of the algal cells is often very rapid: The cells multiply rapidly, but the animals consume them equally rapidly. In these circumstances, the algal cells never develop a large population size or large biomass. Nonetheless, because the algal cells are very productive, the ecosystem can support a substan- tial biomass of the animals, a biomass larger than that ever observed in the algal population. In other words, even though the productivity of the algae is much higher than that of the copepods, the biomass at any point in time of the copepods is greater than that of the algae. In a pyramid of numbers, the widths of the boxes are propor- tional to the numbers of individuals present in the various trophic levels (figure 57.13d). Such pyramids are usually, but not always, upright.

sedimentary cycle: slow, controlled by geologic processes (erosion, deposition, subduction, uplift)

Phosphorus

An example ecosystem

The PondEnergy: e- in -> e- out Cycles through trophic structure Autotrophs Heterotrophs Herbivore Detritivore Carnivore Omnivore Saprotroph/decomposer

stream quality monitoring (SQM) (group 1, 2, 3 taxa)

The Stream Quality Monitoring (SQM) program ensures that the water habitat quality remains high in Ohio's rivers and streams. Rivers and streams in the Ohio Scenic Rivers program are monitored regularly to ensure that the water habitat quality remains high.

biogeochemical cycles = material cycles

The atoms of the various chemical elements are said to move through ecosystems in biogeochemical cycles, a term emphasizing that the cycles of chemical elements involve not only biological organisms and processes, but also geological (abiotic) systems and processes. Biogeochemical cycles include processes that occur on many spatial scales, from cellular to planetary, and they also include processes that occur on multiple time-scales, from seconds (biochemical reactions) to millennia (weathering of rocks). Biogeochemical cycles usually cross the boundaries of eco- systems to some extent, rather than being self-contained within individual ecosystems. For example, one ecosystem might import or export carbon to others.

Ecosystem: Flow of energy

The dynamic nature of ecosystems includes the processing of energy as well as that of matter. Energy, however, follows very different principles than does matter. Energy is never recycled. Instead, radiant energy from the Sun that reaches the Earth makes a one-way pass through our planet's ecosystems before being converted to heat and radiated back into space, signifying that the Earth is an open system for energy. To understand why the Earth must function as an open system with regard to energy, two additional principles need to be recognized. The first is that organisms can use only certain forms of energy. For animals to live, they must have energy specifically as chemical- bond energy, which they acquire from their foods. Plants must have energy as light. Neither animals nor plants (nor any other organisms) can use heat as a source of energy. The second principle is that whenever organisms use chemical-bond or light energy, some of it is converted to heat. the Earth functions as an open system for energy. Light arrives every day from the Sun. Plants and other photosynthetic organisms use the newly arrived light to synthesize organic compounds and stay alive. Animals then eat the photosynthetic organisms, making use of the chemical-bond energy in their organic molecules to stay alive. Light and chemical- bond energy are partially converted to heat at every step. In fact, the light and chemical-bond energy are ultimately converted com- pletely to heat. The heat leaves the Earth by being radiated into outer space at invisible, infrared wavelengths of the electromag- netic spectrum. For life to continue, new light energy is always required.

niche overlap

The niche an organism occupies is the total of all the ways it uses the resources of its environment. A niche may be described in terms of space utilization, food consumption, tem- perature range, appropriate conditions for mating, requirements for moisture, and other factors. The entire niche that a species is capable of using, based on its physiological tolerance limits and resource needs, is called the fundamental niche. The actual set of environmental conditions, including the presence or absence of other species, in which the species can establish a stable population is its realized niche. Because of interspecific interactions, the realized niche of a species may be considerably smaller than its fundamental niche. Gause's principle of competitive exclusion can be restated as: No two species can occupy identical niches indefinitely when resources are limiting. Certainly species can and do coexist while competing for some of the same resources, but Gause's hypothe- sis predicts that when two species coexist on a long-term basis, either resources must not be limited or their niches will always differ in one or more features; otherwise, one species will out- compete the other, and the extinction of the second species will inevitably result.

survivorship

The percentage of an original population that survives to a giv- en age is called its survivorship. One way to express some aspects of the age distribution of populations is through a survivorship curve. Examples of different survivorship curves are shown in figure 55.10. Oysters produce vast numbers of offspring, only a few of which live to reproduce. However, once they become established and grow into reproductive individu- als, their mortality rate is extremely low (type III survivorship curve). In hydra, animals related to jellyfish, individuals are equally likely to die at any age. The result is a straight survivor- ship curve (type II). Finally, mortality rates in humans, as in many other animals and in protists, rise steeply later in life (type I survivorship curve).

qualitative habitat evaluation index (QHEI)

The qualitative habitat evaluation index (QHEI) gives scientists a quantitative assessment of physical characteristics of a sampled stream similar to IBI and ICI biological data. QHEI represents a measure of instream geography.

r = n - m. where n = birth rate (natality) and m = death rate (mortality)

The rate of population increase, r, is defined as the difference between the birth rate, b, and the death rate, d,

intrinsic rate of increase = biotic potential = r

The simplest model of population growth assumes that a population grows without limits at its maximal rate and also that rates of immigration and emigration are equal. This rate, called the biotic potential, is the rate at which a population of a given spe- cies increases when no limits are placed on its rate of growth. In mathematical terms, this is defined by the following formula: dN/dt =riN where N is the number of individuals in the population, dN/dt is the rate of change in its numbers over time, and ri is the intrinsic rate of natural increase for that population—its innate capacity for growth.

Ecology

The study of the interrelationship between organisms and the environment The study of the anatomy of nature The study of the abundance and distribution of organisms the study of how organisms relate to one another and to their environments

lentic/lotic

The term lentic (from the Latin lentus, meaning slow or motionless), refers to standing waters such as lakes and ponds (lacustrine), or swamps and marshes (paludal), while lotic (from the Latin lotus, meaning washing), refers to running water (fluvial or fluviatile) habitats such as rivers and streams.

Population

all members of the same species in a defined area Three characteristics of population ecology are particularly important: (1) population range, the area throughout which a population occurs; (2) the pattern of spacing of individuals within that range; and (3) how the population changes in size through time.

Community

all members of all populations in a defined area refers to the species that occur at any particular locality Communities can be characterized either by their constituent species or by their properties, such as species richness (the number of species present) or primary productivity (the amount of energy produced).

Ecosystem: biodiversity

organisms and their relationships

shelfords law- often more than one element that limits a population

the distribution of a species will be controlled by that environmental factor for which the organism has the narrowest range of tolerance organisms may have a wide range of tolerance for one factor and a narrow range for another (it only takes one physical or chemical variable to limit a species distribution) organisms that have a wide range of tolerance for limiting factors are likely to be widely distributed

liebigs law- law of the minimums

the growth of an organism may be dependent on a number of different factors, however, growth is controlled not by the total amount of resources available, but by the scarcest resource (limiting factor)

Ecosystem: trophic structure

who eats whom. The first trophic level in an ecosystem, called the primary producers, consists of all the autotrophs in the system. The other trophic levels consist of the heterotrophs—the consumers. All the heterotrophs that feed directly on the primary producers are placed together in a trophic level called the herbivores. In turn, the heterotrophs that feed on the herbivores (eating them or being parasitic on them) are col- lectively termed primary carnivores, and those that feed on the pri- mary carnivores are called secondary carnivores. Advanced studies of ecosystems need to take into account that organisms often do not line up in simple linear sequences in terms of what they eat; some animals, for example, eat both primary producers and other animals; we call such animals omnivores. Similarly, some carnivores eat both herbivores and lower level carnivores. Nonetheless, a linear sequence of trophic levels is a useful organizing principle for many purposes. We will follow this approach here, but keep in mind that it is a simplification. Because animal species often eat prey at multiple trophic levels, ecosystems are more like food webs than food chains. An additional consumer level is the detritivore trophic level. Detritivores differ from the organisms in the other trophic levels in that they feed on the remains of already dead organisms; detritus is dead organic matter. A subcategory of detritivores is the decomposers, which are mostly microbes and other minute organ- isms that live on and break up dead organic matter. The productivity of a trophic level is the rate at which the organ- isms in the trophic level collectively synthesize new organic matter (new tissue substance). Primary productivity is the productivity of the primary producers. An important complexity in analyzing the primary producers is that not only do they synthesize new organic matter by photosynthesis, but they also break down some of the organic matter to release energy by means of aerobic cellular respiration (see chapter 7). The respiration of the primary producers, in this context, is the rate at which they break down organic compounds. Gross primary productivity (GPP) is simply the raw rate at which the primary produc- ers synthesize new organic matter; net primary productivity (NPP) is the GPP minus the respiration of the primary producers. The NPP represents the organic matter available for herbivores to use as food. The productivity of a heterotroph trophic level is termed secondary productivity. For instance, the rate that new organic matter is made by means of individual growth and reproduction in all the herbivores in an ecosystem is the secondary productivity of the herbivore trophic level. Each heterotroph trophic level has its own secondary productivity.