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Exam 4 PCB 3043 Ch, 18, 19, 20, 21, & 22
Terms in this set (50)
What are the differences between
the interdependent community and independent community perspectives of Frederic Clements and Henry Gleason?
The species in interdependent communities all rely on each other for survival; species in independent communities do not rely on each other for survival.
Given that the distributions of many animals are determined by the species composition of the plant community, what might you predict about the diversity of animals in an ecotone?
The amount of diversity would be higher than either ecosystem.
How did Robert Whittaker's data on plant species composition along gradients of temperature and moisture in mountains provide evidence against the idea of interdependent communities?
It provided evidence that plants show gradual independent changes in abundance as environmental conditions change. This meaning that the abrupt changes in species distributions may be the result of abrupt changes of abiotic conditions not necessarily meaning that the species are interdependent.
Explain why ecologists consider both species richness and species evenness when they quantify species diversity.
Species richness represents the number of different species in a given ecological community, while species evenness tells us how abundant a species is in a given community. Both are taken into consideration when quantifying species diversity because they include the average of species in relation to their abundance in a community.
Compare and contrast log-normal abundance distributions and rank- abundance curves.
a rank-abundance curve orders species by abundance from most to least; a log-normal distribution groups similarly abundant species together on a bell shaped distribution that uses the log scale on x axis.
Why does an increase in total resources or number of added resources commonly lead to declines in species diversity?
species diversity is usually highest at intermediate values of resources. Increase in total resources causes the species to compete more successfully in comparison to the competitively inferior species to survive.
Explain why we typically find more species under conditions of intermediate disturbance compared to either rare or frequent disturbance.
We find more species under conditions of intermediate disturbance because it is when both types of species can persist, competitively superior species are dominant and small number of species that adapt to disturbances are present as well. This includes both rare and frequent disturbances. Medium intensity: more species.
Why might you expect communities with fewer species to contain fewer trophic levels?
Communities with larger population have more trophic levels in comparison to communities w small population due to larger resources like producers and consumers.
Explain the difference between density- and trait-mediated indirect effects.
Trait mediated indirect effects include effects caused by changes in the distribution of behavior of an intermediate species.
What does it mean when a community is said to exhibit top-down control versus bottom-up control?
Top down control when the abundance of trophic groups is determined by the presence of the predators. Bottom up control when the abundance of trophic groups are determined by the amount of energy available from producers.
How do ecologists distinguish between primary and secondary succession?
Primary succession occurs following an initial devoid of plants and organic soil such as dunes. lava flows' and bare rock while secondary succession occurs with the habitats that contain no plants but still contain organic soil.
When using a chronosequence to document the pathway of succession, what are the assumptions?
the sequence of communities exist over time at a given location meaning that the early successional species are found earlier and the later successional species are found later.
How would a trade-off between dispersal ability and competitive ability affect which types of species could colonize small as opposed to large gaps in a community?
Species with high dispersal ability and low competitive ability are better table to colonize large gaps in a community.
Why should we not expect a single climax community within a biome?
Because the environmental conditions continue changing and progress from small to large life forms. for examples the height of the trees changes in one type of species bc of the difference in shades making the composition of climax community to change.
Compare and contrast the concepts of facilitation, inhibition, and tolerance in the context of ecological succession.
facilitation:mechanism in which one species incases the probability that a second species can become established. inhibition: mechanism in which one species decreases the probability that a second specie will become established. tolerance: new pioneer species neither inhibit not facilitate the growth and success of other species.
If two plant species have similar dispersal and competitive abilities, what factor might help determine which species occupies an early seral stage?
The species which occupies the early serial stage would be the species better able to disperse.
Compare the classic and modern explanations for the succession of ponds and lakes.
succession is the modern model is attributed to the periods of extended drought, while succession in the classic model is attributed to the slow transformation of of ponds being colonized by plants.
When a community experiences succession, why does the species richness of a community initially increase, then plateau, and finally decline?
the pioneer spice initially invades and makes use of all the resources eventually being gradually replaced by more competitive species which makes better use of all available resources.
Why do early- and late-succession species tend to possess different adaptations?
They possess different adaptations because of the tradeoff of high dispersal, rapid growth, and early reproduction w enhances competitive ability.
Why are transient climaxes not stable?
They are not stables because the site is frequently disturbed so a climax community cannot persist. Example, vernal pools fill w water each spring. then dry up in the summer or freeze in the winter.
Why is the efficiency of energy transfer between two trophic levels generally quite low?
Because energy is lost as it is converted from one trophic level to the next, less energy is found in the primary consumers and then the secondary consumers.
How do ecologists distinguish between gross primary productivity and net primary productivity?
GPP is the rate at which energy is captures and assimilated by producers in an area and NPP is the rate of energy that is assimilated by producers and converted into producer biomass in an area. NPP: GPP-respiration.
Compare and contrast the measurement of primary productivity in terrestrial versus aquatic ecosystems.
Measuring primary productivity in the terrestrial ecosystem consists of measuring the CO2 and in aquatic ecosystems it consists of measuring the changes in concentrations of O2.
What factors limit the net primary productivity of terrestrial ecosystems?
the replacement of fine roots and frequent death makes it difficult to estimate the biomass accumulation. herbivory and tissue mortality limits the NPP bc it causes underestimation.
What factors limit the net primary productivity of aquatic ecosystems?
nutrients of phosphorus and nitrogen
Why might assimilation efficiencies be much higher for herbivores eating seeds than for herbivores eating leaves?
Seeds are easier to digest since assimilate energy is the portion of energy that a consumer digest and absorbs.
Why do aquatic and terrestrial ecosystems differ in their pyramids of biomass?
The biomass is greater in producers, and less in the biomass of primary and secondary consumers. While in aquatic ecosystems the pyramid is inverted because the territory consumers are greater along with the secondary consumers and the producers are less (phytoplankton, tiny algae w short lives that are consumed rapidly).
How do changes in stoichiometry affect assimilation efficiencies?
the efficiency of a consumer with a different nutrient ration than its food is reduced.
Why are residence times much longer in forest ecosystems than in aquatic phytoplankton-based ecosystems?
the rate of consumption from the next trophic level in forests is lower than in the aquatic phytoplankton based ecosystem since their rapidly consumed.
How might the carrying capacity for humans on Earth change if the human population ate more plant products than animal products?
it would increase the carrying capacity by over 50 %.
How does energy from the Sun drive the movement of water from the oceans to the continents and back to the oceans again?
the sun causes evaporation from soil and water bodies and evapotranspiration from plants. the evaporated water condenses into clouds that eventually return the water to earth as recitation and the water runs off on the surface or infiltrates the soil. water in the soil is taken up by plants and enters the ground water while excess water returns to the ocean.
How might the ocean reduce the effects of fossil fuel combustion on CO2 concentrations in the atmosphere?
the CO2 that is exchanged with the atmosphere is dissolved and converted into calcium carbonate to precipitate out of water to reduce the effects of fossil fuel combustion
Why is methane gas commonly produced in swamps?
Methane gas is produced in swamps and marshes because oxygen is not readily available to the species in the habitat. Therefore these species can't engage in respiration, so they have adapted by creating a way to oxidize organic carbon to produce methane
Given that the bottom of the ocean is anaerobic, what process in the nitrogen cycle is likely to be occurring in this location?
How might nitrogen-fixing bacteria living in symbiosis with a plant affect the types of environments in which the plant could live?
It would allow the plant to live in areas without much nitrogen
Why is the weathering of bedrock responsible for such a small fraction of the nutrients available to plants?
Because the weathering of bedrocks occurs at a slow rate.
Why do tropical and temperate soils have different rates of nutrient regeneration?
Decomposition increases as temperate increases and increases as precipitation increases.
Explain why agricultural soils in boreal Canada retain their nutrients for many more years than agricultural soils in tropical South America.
They are in a colder environment.
How might global warming cause the release of CO2 from boreal forest soils?
the soil nutrient cycle accelerates meaning microorganisms also accelerate meaning they would metabolize carbon dioxide faster and release in to the atmosphere at a faster rate
What is the chain of events in which the dumping of raw sewage into the Mississippi River leads to fish kills in the dead zone in the Gulf of Mexico?
raw sewage contains nutrients of nitrogen and phosphorus which are dumped into the river. these nutrients are necessary for growth of algae which leads to algae growth in gulf of Mexico. algae bloom produces oxygen but oxygen but phytoplankton/ microorganism uses up all of the amounts of oxygen and leads to death of animals in the water due to oxygen deprivation. this leads to creating a dead zone.
Explain how the fragmentation of a landscape can have both positive and negative effects on biodiversity.
Positive because it increases the amount of edge habitat. negative because small habitats w small populations of species are more likely to go extinct.
Why is it important to consider the quality of the matrix habitat that exists between habitat fragments?
The quality of matrix habitat affects the ability of species to disperse
How do local sampling, regional habitat diversity, and the isolation of continents affect the slope of the species-area relationship?
as area increases there is a proportional increase in species richness
Compare and contrast alpha, gamma, and beta diversity.
Why might we expect that regions with high species diversity will also exhibit high niche diversity?
Why do small islands that are distant from a mainland typically have fewer species than large islands that are close to a mainland?
the large islands are higher in area and closer to resources from the mainland in comparison to the small islands are smaller in area with species that only depend on each other
How has continental drift affected global patterns of biodiversity?
the separation of continents allowed species to independently evolve in different regions of the earth and the joining of continents allowed groups of organisms unique to one landmass move into new areas
In what way might the age and area of a region affect its species richness?
How does knowledge of historic climatic patterns affect our interpretation of present-day patterns of species diversity?
Tropical regions have been limited by the increased differentiation between the poles and equator.
What is the relationship between the length of time the modern continents have been connected and the similarity among the species on each continent?
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