Community Ecology – Flashcards
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Equilibrium theory of diversity
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species diversity-equilibrium point between speciation, immigration, extinction and immigration depends on: species pool (distance to mainland) extinction {higher on smaller islands with fewer resources} vs specation
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Niche
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how an organism makes its living in particular time and place
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fundamental versus realized niches?
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Fundamental niche = where a species can live if it had no predators Realized niche = where a species actually lives including predators
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interference competition
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Interference competition = a direct form of competition (ex. Bullfrogs eating the young of other bullfrogs)
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exploitation competition
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Exploitation competition = an indirect form of competition (ex. Older trees get more sunlight)
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The competitive exclusion principle
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the idea that Two species cannot coexist for long if their niches are too similar - one will be excluded because the dominant species reduces quantity of the resource below some critical level where the other species is unable to maintain its population.
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Predator-prey interactions
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Succession
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orderly change of composition in an ecosystem until it reaches a climax communtiy
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disturbance
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the concept of a climax community
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Intermediate disturbance hypothesis
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Null hypothesis
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a hypothesis that states that nothing will happen
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Invasive species impacts
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impacts- can alter abiotic conditions (moisture of soil)
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Background versus mass extinction
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Background extinction= is the 'normal' extinction rate or standard rate of extinction in Earth's geological and biological Mass extinctions= are significant decreases in the diversity and abundance of macroscopic life over a relatively short period of time (when the rate of extinction increases with respect to the rate of speciation).
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The value of biodiversity
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Do ecosystems return to "normal" after a disturbance?
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There is probably no "normal" in an ecosystem. Ecosystems, if left reasonably undisturbed, tend to go through a predictable series of intermediate communities that eventually result in a climax community. But this climax community is not "normal" or entirely predictable because it may vary depending on biotic and abiotic factors (often random events) that occurred throughout the ecological succession.
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Define "succession" in an ecological context.
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Ecological succession is the gradual and orderly, although not entirely predictable, process of change in an ecosystem brought about by the progressive replacement of one community by another until a stable climax is established.
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What causes species to replace one another in succession?
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The order of ecological succession is influenced by site conditions, by the interactions of the species present, and by the nature of dispersal to the disturbed area (e.g. proximity to other ecosystems, severity of the disturbance, weather conditions, etc). In general, communities in early succession are dominated by fast-growing, well-dispersed species (opportunist or r- selected life-histories). As succession proceeds, these species will tend to be replaced by more competitive (k-selected) species. Often the early species modify the ecosystem in some way that enables the later species to colonize.
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How do the size of an island and its distance from the mainland affect its species diversity?
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The theory of island biodiversity proposes that large islands will experience lower extinction rates because population sizes are larger and competitive exclusion is less likely; the equilibrium level of species diversity is therefore higher. Islands that are closer to the mainland experience a higher rate of immigration; the equilibrium level of species diversity is therefore higher the closer an island is to the mainland.
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Why does Diversity decreases towards the tip of a peninsula?
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Biodiversity decreases towards the tip of a large peninsula because it is much like an island with species migrating in via its base. Therefore the tip of the peninsula is farther from the "mainland" compared to its base.
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Ecological niches
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describes how an organism or population responds
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Climax Community
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a theoretical "final" stage of a particular secession characterized by slow rates of change compared to younger or more disturbed area
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What is Zonation?
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patterns of species abundances distribution in response to an abiotic gradient (biotic factors play a part as well)
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Species diversity
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# of species that occur within the community (richness) and their relative abundance (% each contributes to the total number of individual of all species) diversity DOES NOT alway correlate with abundance!
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What is the difference between primary and secondary succession? How do the early physical and biological environments differ between these types of succession?
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Succession that begins in areas where no soil is initially present is called primary succession (e.g. lava flow, land left by a retreating glacial, or severe landslide), whereas succession that begins in areas where soil is already present is called secondary succession (e.g. an abandoned field, clear-cut forest or construction site).
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Early conceptual models of succession emphasized what factor as the principal control on vegetation turnover? Later models refined this, and included what other biotic interactions and physical environmental factors?
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Early models of succession emphasized soil characteristics as the principle control on vegetation turnover - early colonizers changed the soil composition, enabling additional colonizers, etc. This is probably true but other abiotic and biotic factors are important as well. For instance, interactions between the species present and the random events (both biotic (e.g. proximity of nearby communities, competition between early settlers) and abiotic (e.g. weather and season)) that determine dispersal of seeds to the disturbed area have significant impact on the composition of the community.
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How might predation, parasites, and herbivores decrease diversity? How can they increase diversity?
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Predation, parasites and herbivores can either increase or decrease diversity in an ecosystem depending on the nature and intensity of the interaction. High intensity and monospecific predation, parasitism, and herbivory usually decrease diversity because they overwhelm the target population (overgrazing rangeland with cattle can lead to desertification for instance). Low intensity predation, parasitism, and herbivory can increase diversity by preventing competitive exclusion and weakening the dominant competitor.
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What is the Intermediate Disturbance Hypothesis? Why is diversity often highest in the middle stage of succession?
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The intermediate disturbance hypothesis states that intermediate levels of disturbance (moderate but relatively frequent) open space for colonization and initiate a cycle of succession of species, resulting in a mosaic of habitat patches rather than a more stable and less diverse climax community in which all the resources are utilized. In other words, an area of habitat may form a patchwork of communities, each at different stages of ecological succession. Thus, disturbance and recovery potentially enable much greater biodiversity than is possible without disturbance.
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Traditional farming involves creating disturbance and then fighting secondary succession. Explain.
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Farmers clear land in order to cultivate their crops - this removal of the existing community is the disturbance. Cultivating crops is fighting secondary succession because the farmers are trying to prevent weeds (opportunist, r-selected species) from outcompeting their crops. Only weeding and/or the use of herbicides allow the crops to grow unimpeded in the new ecosystem.
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What do scientists think caused the five great mass extinctions in the past?
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These mass extinction events were probably primarily the result of climate change due to abiotic factors (e.g. meteors, volcanoes, etc).
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what factors are causing the 6th extinction
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The 6th extinction is anthropogenic: - Climate change - Pollution - (declining habitat quality - deserts spreading; water and atmosphere polluted) - Transformation of landscape/destruction and reduction of habitat - 35% of land surface used for crops and more for grazing - Tropical forests are being cut at 17 million ha per year - Overexploitation - Invasive species
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Define and give two examples of resource partitioning. How does it allow species to avoid overlap of their fundamental niches?
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If two species with similar niches coexist, then they share the resource, each exploiting it in a slightly different way. Although they do not come into direct competition for at least part of the limiting resource, this usually leads to a decrease in both species' potential for growth because it limits their access to the resource. Examples include birds living on the sandy shore in Figure 8-9 on page 182 in your textbook; fish living and feeding off different parts of a kelp forest - canopy, midwater, holdfast, sea floor.
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What is the competitive exclusion principle?
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Two species cannot coexist for long if their niches are too similar - one will be excluded because the dominant species reduces quantity of the resource below some critical level where the other species is unable to maintain its population.
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What happens when 2 species occupy the same niche and compete for the same recourses?
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- One species goes extinct and the other utilizes the resource (competitive exclusion). - One species migrates to another area. - One or both species shift(s) habits/behavior through natural selection and evolution to occupy a different niche - resource partitioning. - One species suffers a significant population decline and occupies a much smaller, realized niche compared to its fundamental niche.
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How do the size of an island and its distance from the mainland affect its species diversity?
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The theory of island biodiversity proposes that large islands will experience lower extinction rates because population sizes are larger and competitive exclusion is less likely; the equilibrium level of species diversity is therefore higher. Islands that are closer to the mainland experience a higher rate of immigration; the equilibrium level of species diversity is therefore higher the closer an island is to the mainland.
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What factor let someone understand a community?
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A community is an assemblage of plant and animal populations that live in a particular area We try to understand communities by describing patterns: - scale (physical appearance) - spatial and temporal structure - species diversity - trophic and niche structure - succession and disturbance
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Define Niche
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how an organism makes its living in a particular time and place (does not include habitat)
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Fundamental Niche
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theoretical niche or all the space/resources a species COULD use
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Realized Niche
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actual niche that a species utilizes
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Niche differentiation
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natural selection favors individual that do not compete
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Competitive exclusion principle
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in a controlled lab in which 2 species compete for the sam resource, one will out compete the other entirely
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Predation
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the preying of one animal on others
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Parasitism
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Parasitism is a relationship between two different organisms where the parasite harms the host. When worms live in a dog and take nutrients from the dog, this is an example of parasitism. (online deff)
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Resource partitioning
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Specialization-a way around competition - each species specializes and exploits only part of resource
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speciation
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evolutionary process through which new species emerge
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Specialists Vs Generalists
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Generalists: Species that can live in many different types of environments, and have a varied diet. Specialists: Animals that require very unique resources. Often, these species have a very limited diet, or need a specific habitat condition to survive.
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Co-Adaptions
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In co-evolution, where the existence of one species is tightly over bound up with the life of another species, new or 'improved' adaptations which occur in one species are often followed by the appearance and spread of corresponding features in the other species.
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Adaption and Natural Selection
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Adaptions happen because of natural selection Natural Selection is the gradual process by which biological traits become either more or less common in a population or differential reproductive success of organisms interacting with their environment.
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