quiz 4
Which of the following is true about farmers using ants as keystone species to reduce pest populations in agricultural ecosystems?
-Ants control the population of large bodied citrus pests - China has been controlling insect pests of orange orchards for over 17 centuries
Select all of the following statements that are true for the rank abundance curve shown below?
-Community a is dominated by one species. -In community b, each species is represented equally compared to the rest of the species.
Identify the way(s) in which keystone species influence the structure of communities.
-Keystone species will keep several of the prey populations below the carrying capacity of the community. -Keystone species will increase species diversity within the community. -If the keystone species is removed from the community, the community structure can collapse.
Which of the following nutrient cycle studies are playing prominent roles in science today?
-Phosphorus -Nitrogen - Carbon
Which of the following statements best explain the difference between gross primary production and net primary production? Check all that apply
-Plants utilize some of the incoming energy derived from photosynthesis for their own self-maintenance. -Plants and algae carry out both photosynthesis and cellular respiration.
Which of the following describes secondary succession?
-Supports life immediately after a disturbance -Occurs after a fire -Occurs after a tornado -Soil present -Severity varies, but it is never completely lifeless
Identify the results obtained by Orrock, Witter, and Reichman that support their hypothesis that the relationship between Brassica nigra and Nassella pulchura is apparent competition.
-The distribution pattern between Brassica nigra and Nassella pulchura suggest competition. -B. nigra actually suppresses N. pulchra indirectly by sheltering mammalian herbivores that feed on the native grass.
Identify the statements that explain why the exports and inputs of phosphorus in the Bear Brook ecosystem can change.
-The peak in phosphorus input was associated with autumn leaf fall due to the deciduous nature of the Bear Brook ecosystem. -The annual pulse of spring snow melt results in an increased export of phosphorus.
Complete each sentence with the correct term. Any relatively discrete event that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment is called a ______________ Sousa studied the effects of disturbance on the diversity of intertidal algae and invertebrates and found support for the__________ hypothesis. Diversity of prairie vegetation is lowest in areas receiving____________ levels of disturbance.
-disturbance -intermediate disturbance -low and high
The feeding activities of a keystone species may control the structure of communities. Paine (1966, 1969) proposed that keystone species affect community structure in specific directions. Complete each sentence with the correct term describing his research. -Paine predicted that some predators may_________ species diversity in intertidal communities. -This outcome is predicted because some predators___________ the probability of competitive exclusion by lower trophic levels.
-increase -reduce
Complete each sentence about interactions between beavers and the leaf beetle, Chrysomela confluens. When activities of one species indirectly benefit another species without itself being helped or harmed, this is an example of_________ Where beaver foraging activity was was greatest, beetle densities were _________. Beaver are______________ by the defensive leaf chemistry of felled cottonwood tree leaves Leaf beetles are__________ by the defensive leaf chemistry. The leaf chemistry of sprouted cottonwood leaves_________ leaf beetles and explains higher densities on beaver felled trees.
-indirect commensalism -higher -repelled -not repelled -benefited
Complete each sentence with the correct term. Experiments manipulating species during succession of the intertidal zone by Sousa show evidence of___________ of later successional species. Turner's studies of intertidal plants and algae indicate evidence that____________ is important during succession of the intertidal zone. Keever's experiments on the temperate forests of the Piedmont Plateau indicate that__________ are important mechanisms of succession during early succession.
-inhibition -facilitation -facilitation and inhibition
Complete the following sentences about the nitrogen cycle. In this anaerobic process, bacteria convert N2 to ammonia, a form of nitrogen more readily used by plants.___________ In this process, bacteria convert ammonium to nitrate.__________ This anaerobic process releases N2 from the organic matter pool to the atmosphere._________ This process is the most common pathway for nitrogen to enter the soil by fungi and bacteria during decomposition._______________
-nitrogen fixation -nitrification -denitrification -ammonification
In pristine, tropical surface marine waters, what factors limit primary productivity? Check all that apply.
-phosphorus -nitrogen
Complete each sentence with the correct term. The number of species in a community is called________ . The relative abundance of species in a community is called_________ . A combination of the number of species and their relative abundance defines____________ .
-species richness -species evenness -species diversity
Meyer and Likens (1979) studied the long-term dynamics of annual phosphorus inputs and exports of Bear Brook in New Hampshire. Complete each sentence based on results of their study. The ratio of annual phosphorus inputs to exports varied from 0.56-1.6 and varied depending on__________ . During high flow years the phosphorus export was __________than inputs. During low flow years, the phosphorus export was_____________ than inputs.
-stream discharge -greater -less
Identify after which disturbance primary succession occurs. Check all that apply.
-volcanic eruption - glacial retreat
A community has four species, two with 20 individuals and two with 30 individuals. What is the value of the Shannon-Wiener index?
1.366
What type of relationship exists between nitrogen levels in the soil and the diversity of ectomycorrhizal fungi?
A high level of soil nitrogen in the organic horizon corresponds to a decline in the diversity of ectomycorrhizal fungi.
Which research project will give the most accurate estimation of species diversity within the community and produce a more complete lognormal curve?
A sampling of a 5 acre plot of tropical rainforest that discovered 279,200 individuals.
Which combination of soil nutrients and their corresponding levels has been found to create distinct growing conditions that allowed for a stable coexistence of phytoplankton species?
A stable coexistence of phytoplankton occurred when the levels of phosphate and silicate were in balance with each other.
Which of the following organisms tend to dominate areas in which phosphorous is a limiting factor?
Algae
Grimm attributes most nitrogen retention by the Sycamore Creek ecosystem to uptake by algae and invertebrates, since levels of nitrogen retention are consistent with the rates at which nitrogen was accumulated by algal and animal populations. What conclusion can you draw from looking at the graph of nitrogen retention in Sycamore Creek after flooding?
Algae and other invertebrate populations reached peak levels around 30 days after flooding, then began to decline.
Identify the effects that habitat disturbance by humans has upon diversity.
All of these are effects that human disturbance of habitat has upon diversity.
What type of relationship is exemplified by a graph showing the relationship between soil fertility and plants species that have a mycorrhizae relationship?
As the soil fertility of the community decreases, the diversity of plant species plants with mycorrhizae relationships found within the community will increase.
Which of the following organisms increased species diversity with increasing environmental heterogeneity?
Birds
Which statement about intertidal zone disturbance is correct?
Boulders of medium size will experience the greatest degree of diversity due to having an intermediate level of disturbance.
Identify the geologic feature that most affects community resilience in Sycamore Creek.
Distribution of bedrock
During the __________ stage of succession in Glacier Bay there is a net inhibitory effect on spruce seedlings.
Early or pioneer
Contrast the movement of energy and nutrients in ecosystems.
Energy is not recycled within ecosystems, whereas nutrients are used over and over.
Which of the following is described as pioneer species modify the environment in such a way that it becomes less suitable for themselves and more suitable for species characteristic of later successional stages?
Facilitation model
Which of the following is described as early occupants of an area modify the environment in a way that makes the area less suitable for both early and late succession species?
Inhibition model
Based upon this diagram, what type of hypothesis can be formed in regard to species diversity?
Intermediate levels of disturbance promote higher levels of diversity.
How does emphasizing strong interactions make the structure of food webs more comprehensible?
It emphasizes the more biological significant trophic interactions and simplifies food web structure.
Identify the statement that best describes the key difference between a keystone species and a foundation species.
Keystone species have a low level of biomass within the community while foundation species have a high level of biomass.
Choose the answer that best describes a trophic cascade.
Lake trout are introduced into a lake and reduce the abundance of the native cutthroat trout that feed on small zooplankton. This results in an increased abundance of small zooplankton.
Which of the following contains the largest pool of phosphorus?
Marine sediments
Chapin and colleagues (1994) have described the change in soil properties during succession at Glacier Bay, Alaska. What soil properties increase during succession?
Nitrogen - Organic matter content -Soil moisture
How do the soils of Hawaiian ecosystems change over very long periods of time, that is, over the course of millions of years?
Nitrogen losses from these ecosystems increased over time, while phosphorus losses decreased.
Which of the following describes primary succession?
No plants, animals, or microbes present -Bare ground, no soil -Occurs after a volcanic eruption -Occurs after glacier retreats
Which term is used to describe the dynamics of nutrients within a stream ecosystem?
Nutrient spiraling
Paine proposed that feeding activities of a few species have inordinate influences on community structure. To test his hypothesis, what trophic level did he manipulate in the intertidal zone of Mukkaw Bay, Washington and New Zealand?
Paine removed the top predators.
Which set of results would support the hypothesis that the interaction between Brassica nigra and Nassella pulchra is actually direct competition?
Researchers found a gradient of decreasing herbivore pressure away from B. nigra patches, producing a gradient of increasing density in the N. pulchra population with distance from B. nigra patches.
Which statement about the N:P ratio of aquatic vertebrates is correct?
The higher the phosphate content in the body of the organism, the lower the N:P ratio and the lower phosphate levels in their excretions.
Choose the statement that best describes the results of the study of species richness of bird communities along a gradient of land use intensity by Blair (2004).
The highest species richness of birds occurred at intermediate levels of land use intensity.
What is necessary in order for a species to be considered a foundation species?
The species must have a substantial influence on the community structure as a consequence of its high biomass.
Identify the correct changes to spiraling length if V and T both decreased.
The spiraling length would be shortened.
Which of the following is described as initial stages of colonization are not limited to a few pioneer species, juveniles of species dominating at climax can be present from the earliest stages of succession, and species colonizing early in succession do not facilitate colonization by species characteristic of later succession stages?
Tolerance model
Ecological efficiency can limit the number of trophic levels in an ecosystem.
True
Grasslands have higher net primary productivity compared to tundra.
True
The rate of decomposition within an ecosystem affects the rate at which inorganic nutrients are made available for use by primary producers.
True
Which statement best describes how the beavers indirectly benefited the leaf beetle?
When the beavers cut down the cottonwood trees they caused the tree stumps to secrete defensive toxins that the beetles could use for their defensive mechanisms.
What conclusion can be drawn about the relationship between foliage height and warbler diversity from this graph?
With an increase in the volume of foliage there is a corresponding increase in the number of species of warblers.
Diversity indices such as the Shannon-Wiener index, are
a measure of the numbers of species and the relative abundance of each species.
Studies of which nutrient cycle have been able to provide society with crucial information regarding global climate change?
carbon
As the nutrient retentiveness of a stream increases, the spiraling length of nutrients increases.
false
Increased primary production fosters lower secondary production in terrestrial and aquatic ecosystems
false
The conversion of a substance from the organic form to the inorganic form is called __________.
mineralization
A foundation species is best defined as
organisms, such as abundant, forest tree species or coral reef species, that substantially influence community structure as a consequence of their abundance.
A keystone species is best defined as
species that, despite low biomass, exert strong effects on the structure of the communities they inhabit.
Complete each sentence with the correct term. The persistence of a community or ecosystem in the face of disturbance is called_________ . The capacity of a community or ecosystem to recover structure and function after a disturbance is_________ . The capacity of a community or ecosystem to maintain structure and/or function in the face of a potential disturbance is_________
stability -resilience - resistance
Examine the processes of ecological community change by completing each sentence. Then, arrange the sentences in a logical paragraph order. The gradual change in plant and animal communities following disturbance or the creation of new substrate, is a process known as ecological _____________. Ecologists define two types of succession. When an existing community has been disturbed and organisms slowly reestablish in the area, such as when plants become reestablished in a wooded area that has been cleared______________, succession is occurring. On the other hand,__________ succession can begin on areas of bare rock or where soil has not been formed. The first species to inhabit an area undergoing such primary succession form a ______community. Given enough time and lack of disturbance, primary succession ends with a ______community, whose populations remain relatively stable and are characteristic of the region.
succession -secondary - primary -pioneer -climax
Ratio-dependent predator-prey models predict
that primary consumer abundance will increase proportionally to the level of enrichment.
Mineralization is best described as
the breakdown of organic matter from organic to inorganic forms during decomposition.
The relative abundance of a wide variety of organisms approximates a lognormal distribution. For most of these distributions, only a portion of the bell-shaped curve is apparent because
the sample sizes are relatively small.
Annual Actual Evapotranspiration (AET) is positively correlated with net primary productivity in terrestrial ecosystems.
true
Based on the study by Peierls et al. 1991 of 42 major river systems, as human population density within river basins increases, the concentration and export of nitrate increases.
true
Studies of nitrogen retention in the Hawaiian Islands and Sycamore Creek both found a similar pattern of increasing retention early in succession followed by decreasing retention later in succession
true
