The ways in which humans affect the various levels can be found here..
(PDF is here)Introduction to Ecology (PDF format for printing)
Click on the evolutionary ecology box in figure one. Evolutionary ecology is concerned with how mutations relate to genetic variation and how this variation is maintained in nature. Evolutionary ecologists also study the effects of inbreeding, genetic drift, neighborhoods, and genetic bottlenecks. Generally, reducing the variation in a population and will leave open to extinction. Genetic drift is a phenomenon seen in small populations. Small populations may lose and gene that is in low frequency, which can affect their evolution. Individuals within a neighborhood may preferentially breed within their neighborhood causing the gene pool of one neighborhood to differ from another. Evolutionary biologists are also interested in natural selection, speciation, and evolutionary trends. Return to the previous page.
Now click on the behavioral ecology square. Behavioral ecologists are interested in how behavior adapts a species to the environment. They determine, for example, how an individual assesses, obtains, and defends a resource. As an example, a researcher might be interested in how a red wing blackbird decides which area is best for nesting, how it fights with neighbors to procure that area, and maintain a territory through defence. The researcher might also be interested in how much energy and individual blackbird expends in defending his territory and how that energy expenditure eventually equates a higher reproductive fitness. Behavioral ecologists are also interested in intraspecific competition, mating systems, you’re a sexual selection. Go back to the previous page.
Now click on the population ecology square. Population researchers are interested in intrinsic growth models of population increase. That is, what physiological, anatomical, and behavioral features are built into a population to allow it to grow. Why for example, do some birds had a clutch size of ten nestlings while others only produce a single offspring? They are also interested in mutualism and commensalism and their effects on growth. How do these relationships affect reproduction, fitness, and population growth? Many population ecologists are interested in the effects of competition on growth. When two species need a resource that is in short supply (say, seeds for birds), then one or the other species (or both) may not be get enough food to reproduce. Finally, these researchers are interested in how herbivory, predation, and parasitism affect growth and the distribution of a species. Go back to the previous page.
Now click on the community ecology square. Community ecologists explore the different types of community structure, such as deserts, grasslands, rain forests, and marine systems. They determine the relationship between species diversity (a measure of how much variation there is in a community) and community stability. At the ecosystem level they may explore energy flow, productivity, and nutrient cycles. Return to the previous page.
Click on physiological ecology. Physiological ecologists determined the biochemical and physiological adaptations that allow an organism to exist in a particular habitat. What is required, for example, for an animal or plant to exist in the desert habitat? Both need to retain water. Plants often do this with a thick, waxy integument, along with other adaptations to conserve water. Animals may develop specialized behaviors and kidney systems to conserve water. Physiological ecologists often determined the abiotic (non-living: humidity, temperature, etc.) factors that affect distribution and dispersal of the species. Return to the previous page.
Mathematical ecology uses equations to describe the behavior, growth, and interactions among organisms. Often these ecologists produce models that are predictive. Such models are often used in agriculture time when planting, insecticides, irrigation, and other actors should be applied to a field. Return the previous page.
Applied ecology is concerned with the effects of humans have on ecosystems. They explore how habitat destruction, exploitation of species, and pollution affect survival of a species. Return the previous page.
Most research in ecology is ultimately tied to the problems of species distributions and abundance (Fig 2). Sometimes a single species is of interest, while more often the research is concerned with assemblages of species (e.g. descriptions at the community level). Although many of the earlier investigators were content to quantify population parameters for their favorite species in a variety of habitats, most of the recent research attempts to determine the environmental factors (abiotic factors) and species interactions (biotic factors) that may explain the observed patterns.
Figure two shows an example for the distribution and abundance. Under distribution, we have an example of the Louisville metropolitan area. The light blue areas are those with high moisture content. Notice that individuals of the species under investigation (shown as red dots) are found most often in the high moisture areas. The distribution of these organisms is clearly related to moisture availability. Under abundance we have an example of several species' population growth over time. Under these experimental conditions only three species, represented by the purple, green, and yellow lines, survived over the experimental period.
ECOLOGICAL LEVELS
As recently as a few years ago, the biosphere (Fig 3) was thought to be a thin layer
where life could exist on the surface of the earth. It extended only a few meters
below the earth's surface on land down to the lower levels of the oceans. Life was
thought to exist only a few 10's of miles into the atmosphere. Today we know that
bacteria known as extremophils can exist miles below the earth's surface and the biosphere
has expanded accordingly.
An ecosystem (Fig 4) consists of all the organisms and non living materials found in a particular area. The organisms interact with one another as well as with the non living components of the environment. The flow of energy through the ecosystem and the recycling of nutrients within the system are of considerable interest to ecosytem ecologists.
A community is described as a group of interacting organisms found in the same general area (Fig 5). Depending on the detail of the analysis, a description of the community may include microorganisms, fungi, protists, animals, and plants. In other cases, a researcher may concentrate on only a few species in the community.
The population level of organization is characterized by a group of potentially interacting organisms of the same species (Fig 6). Populations and their behavior is composed of a collective behaviors of individuals (Fig 7).
Each of these ecological levels has emergent properties are not seen at other ecological levels. For example, the biosphere may be divided into broad areas of land mass known as "biomes" (Fig 8). Each biome has its home characteristic climate, vegetation, an animal groups. Such levels of organization are not seen below the level of the biosphere.
The ecosystem is composed of both living (biotic) and non living (abiotic) factors. Under the biotic factors are shown organisms associated with a pond ecosystem. In this example, the living portions of the pond include birds, such as ducks & black birds, flowering plants, trees and grasses, and insects. The abiotic or non living portions of the ecosystem include energy from the sun, wind, temperature fluctuations, salinity, and water quality. Both the biotic and abiotic portions of this system work together in a common ecosystem.
Figure nine shows a food web for an African savannah community. All of the organisms feed on the grasses and trees at the base of this community. These green plants are present the first feeding level (trophic level) and are the producers in this system. Plant eating animals such as the rabbits occupy the second tropic level and are considered to be primary consumers. The primary consumers are fed upon by carnivores (tertiary trophic level) such as the lion and wild dogs. These organisms occupy the top of the food web. Energy flows through this community from the plants through the primary consumers and up to the top carnivores.
At the level of the population we have social behavior, population growth, and population demographics (Fig 11). Individuals have their own behaviors, such as a vocalizations of a frog or the courtship behavior of a male duck (Fig 12). In addition, individuals have their own physiological adaptations that allow them to survive under periods of environmental stress.
FACTORS AFFECTING THE DISTRIBUTION OF AN ORGANISM
The habitat is the physical portion of the environment while the
ecosystem is the interaction among organisms (communities) and their
habitat. Habitat features are abiotic (non-living) and include
temperature, oxygen levels, pH, wind speed, "lay of the land", current, etc. For
any of these factors there is a tolerance range over which a species is
able to survive (e.g. physiological limits for the species). Goldfish, for example, prefer
temperatures between 6 and 36º C while brook trout have a tolerance range of 0.5 - 25º
C. More on this later.
Figure 13 shows a flow diagram that could be used to explain why a species has failed to colonize a particular habitat. Click on each of the boxes for more information on dispersal, behavior, other species, and physical or chemical factors.
The ways in which humans affect the various levels can be found here..
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Introduction to Geographical Information Systems Assignment (PDF is
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