Ecology Ch. 17

In conducting a study of trophic relationships in a stream community, you record the following data for the six species you observed. Which species would most likely be the foundation species for this community? E

Species	Number Observed	Total Biomass (kg)
A	103	192
B	231	94
C	87	132
D	435	234
E	78	257
F	31	71

In the following, simplified food chain, which pairs of species have indirect interactions?

Sp. A >> Sp. B >> Sp. C >> Sp. D

Sp. B and Sp. D; Sp. A and Sp. C

Rank the snail density conditions in order of increasing algal species richness. In other words, which snail densities produced lowest, middle and highest algal richness.

High snail density >> low snail density >> middle snail density

In Power’s experiments, she was trying to determine whether trout and roach were acting as keystone species

A keystone species would be considered to be a type of foundation species

By burying seeds, ants help plants avoid which of the following sources of mortality?

Rodents, fires

Apparent competition is a type of indirect interaction

In representing the communities in Cano Volcan, one approach used by Winemuller was to exclude the most common species

In a commensal relationship between two species, one species is benefited while there is neither harm nor benefit to the other

Which of following interactions are considered to be strong interactions in Tscharntke’s food web of a Phragmites community? Phragmites-G.inclusa; T.arundinis-C.caerulus; Phragmites-A.geminipuncta

Which three of the following factors did Lubchenco propose to be necessary in order to resolve the conflicting results of herbivore – diversity experiments? Herbivore food preference; location-based changes in competition and food preferences; local competitive relationships

In addition to feeding on invertebrates, the roach (fish) will also eat algae

Food webs are used to represent feeding relations within a community

In environments where Littorina’s feeding preferences is the competitively inferior alga taxa, rank the density conditions in order of increasing algal species richness with the lowest at the bottom. In other words, which snail densities produce the lowest, middle and highest algal richness? Low snail densities >> middle snail densities >> high snail densities

The activities of cleaner fish are considered to be an example of mutualism

In his research in Mukkaw Bay on the role of predators in community diversity, the control treatments for the experiment received no predators

A disease wipes out most of the trout in the Eel River. Which of the following populations would you expect to increase as a result of this? Predatory insects; roach fry; Cladophora

Stem-boring by larvae of A.geminipuncta are responsible for inducing Phragmites to produce side branches

The purpose of the exclosure cages in Power’s experiments was to exclude Steelhead trout from the study plots

Indirect interactions between two species requires an intermediate species

Which of the following trophic interactions were observed in the Phragmites community studied by Tscharntke? Arrows indicate the direction of energy flow, eg. A >> B, indicates that A is eaten by B

Phragmites >> fly (G.inclusa); fly (G.inclusa) >> Blue Tits; Phragmites >> moth (A.geminipuncta)

In representing the communities in Cano Volcan, one approach used by Winemuller was to exclude the weakest trophic links

Predators that keep prey populations below their carrying capacity and prevent competitive exclusion by one of these species are known as keystone species

Algal species richness was greatest at which snail density? Middle

Lubchenco’s research on the relationship between herbivores and community diversity was motivated by conflicting results in previous experiments. TRUE

Species that have a substantial influence on community structure due to their high biomass are referred to as foundation species

In the tide pools in which Lubchenco removed snails, the abundance of the alga Enteromorpha increased, while the alga Chondrus decreased relative to the control treatment.

Experimental removal of cleaner wrasses from reef patches by Bshary resulted in a decrease in the number of fish species on the patch

Lubchenco conducted the feeding preference experiments with snails in the laboratory

The purpose of the control treatment, in the experiment by Orrock et al., was to account for disturbance effects

A disease wipes out most of the trout in the Eel River. Which of the following populations would you expect to increase as a result of this? Roach fry; predatory insects; Cladophora

In the intertidal food web of Mukkaw Bay, a seastar is considered to be the top predator

Weaver ants obtain liquids and carbohydrates from mealy bugs

Yang found that the weaver ants did not attack parasites of the mealy bugs

In response to the removal of starfish, the space occupied by the barnacle Balanus increased

Redford has proposed that human hunting has undermined the role of keystone species maintaining diversity in rain forest communities

The ability of the predaceous fire ant to act as a keystone species in arthropod communities is a benefit for corn and squash farmers

The sprouts growing from trees felled by beaver have leaves that are more nutritious for the beetles than those growing on mature trees

After a local population explosion of sea gulls, you would expect to find an increase in abundance of the alga Chondrus in the tide pools

In the intertidal food web of the Gulf of California there are a total of 11 predators in the system

Lubchenco studied the relationship between algal abundance and snail densities in tide pools

Bshary observed the number of fish species on reef patches and the presence or absence of cleaner wrasses

The most influential trophic relationships in a food web are known as strong interactions

Removal of predatory fire ants from corn and squash fields would likely lead to an increase in crop damage from insect pests

Which one of the following would best represent food web control on the population of the snail Littorina? Snail >> crab >> seagull

Lubchenco conducted the snail removal experiments in tide pools

Yang found that the weaver ants function as a keystone species in orange trees by feeding on larger insects

In defining “strong interactions”, Paine felt that the most important factor in defining community structure was the degree of influence, but not the energy flow of interactions

Which of the following represents the indirect commensalism observed by Martinsen et al.?

Beaver – cottonwood – beetle

In feeding preference experiments with snails, Lubchenco found that small tender algae were generally preferred over those that are tough and perennial

In the intertidal food web of the Gulf of California, a seastar is considered to be the top level predator

The weaver ants have a mutualistic relationship with mealy bugs – the ants receive fluids and carbohydrates while the mealy bugs benefit from protection from predators

Redford considers species that have had their densities reduced to the point that they can no longer function as keystone species as ecologically extinct

In Power’s study of stream communities, trout performed a similar function as a keystone species to the snails in Lubchenco’s experiments in tide pools

In Lubchenco’s study of tide pools, the snail Littorina performed a similar function to the Pisaster in Paine’s Mukkaw Bay experiments – controlling the populations of the dominant space competitor

Littorina’s preference for feeding on the competitively dominant alga could produce the pattern of algal richness seen by Lubchenco

In his New Zealand experiments, Paine found that removal of a sea star resulted in an increase the area occupied by a mussel

Paine concluded that greater numbers of predators in a community produces increased predation pressure, leading to an increase in diversity of the community

In looking at the communities on islands created by a dam impoundment that excluded large predators, Terbough observed changes to community structure that were so large that he described them as an ecological meltdown

Removal of the seaweed Durvillea enhanced the effects of only removing the seastar from the intertidal zone in New Zealand

Consistent with their hypothesis that about apparent competition between mustard and bunch grass, Orrock et al. found bunch grass did better when rodents were excluded

Lubchenco’s research supported that of Paine, showing that a single species could control the diversity of a community

Paine found that as the number of species in a food web increased, there was an increase in the number of predators in the community

At high densities, Littorina needed to switch to feeding on less preferred alga species in order to meet their energy needs

In looking at the role of large predators, Terbough found that medium-sized mammals are more abundant when the predators are absent

Paine also conducted a series of experiments that removed the seaweed Durvillea, which is also an important space competitor

As a result of their experiments, Orrock et al. proposed that the rodents use mustard for protective cover, feeding on the bunch grass

Ecology Ch. 16

Human disturbance is widespread and comes in many forms including: increased urbanization; air and water pollution; removal of forest

Plants that are described as a vine would belong to the same life-form

Generally, there is a positive relationship, or correlation, between environmental complexity and species diversity

In tropical forest communities, the distribution of plant communities are strongly influenced by soil characteristics

One of the most ubiquitous patterns found in communities is that very few species are common; very few species are rare; most species are moderately abundant

In a tropical forest, a particular area may have many unique plant communities

Abiotic forces of disturbance would include fire; flooding

Studies by Jordan (1985) showed that in tropical Amazon forests, a change of elevation greater than 2 meters above nearby streams would have sandy well-drained soils that can cause water stress in plants

Species diversity is based on which two factors? The relative abundance of species in a community; The number of species in a community

Sousa’s work demonstrates that disturbance may allow multiple species to coexist because the disturbance prevents competitive exclusion

As a general rule, very few species are very abundant; very rare

There are many definitions of disturbance; however, most have this in common: they remove individuals or biomass; they allow for the establishment of new individuals or colonies; they are discrete physical events

The value of a rank-abundance curve lies in its ability to visually portray species richness and evenness in a two dimensional graph

Species diversity includes the number of species in community

Which are components of a community’s structure? The number of species present; The relative abundances of species; The kinds of species present

Imagine a community consisting of approximately 100 species. Considering the patterns of species abundances, one would expect to find very few of the species to be very abundant

Groups of species that live in a defined area and interact with each other are termed a community

According the IUCN in 2007, the most serious threat to species diversity is habitat loss

A discrete event that removes individuals or biomass and creates space for new individuals to become established is known as a disturbance

In a typical community, most species will be moderately abundant

Which of the following are soil characteristics important to plants? Depth to the ground water; type of soil (sand or clay); pH

The niches of plants and algae can be defined by physical characteristics such as moisture; their nutrient requirements; chemical characteristics such as pH

At similar latitudes, community A has many more species than community B. what is one possible explanation for this observation? Community A has a higher habitat heterogeneity than community B

The intermediate disturbance hypothesis that the highest level of species diversity is found in communities with continually changing conditions

In temperate grasslands, disturbances can include fire; trampling; grazing

Species evenness is also known as the relative abundance

When environmental conditions remain relatively the same over a time period, the community is said to be in equilibrium

Based on studies by MacArthur in the 1950s, communities with more complex forests contained more species of warblers than other plant communities

As nutrient levels increase in aquatic communities, plant and algae diversity decrease

The highest rates of species diversity is often associated with an intermediate level of disturbance

Tilman’s work in 1977 showed that some diatoms can coexists when the ratios of essential nutrients were correct

A rank-abundance curve with a steep curve is indicative of a community dominated by a few abundant species and lower species richness

In forest communities, the foliage height diversity varies with species richness; species evenness

Very low levels of disturbance will reduce species diversity because only the best competitors will survive

The total number of species within a community is known as the species richness

Prairie dogs create disturbance in a grassland by grazing the on the plants creating bare ground; creating burrows and depositing soil into mounds

When the number of individuals in a community are plotted by the number of species, the typical result is a lognormal distribution

Based on the figure illustrating lognormal distributions, what do forest birds and desert plants have in common? Very few species are very rare; most species have moderate coverage or abundances; very few species are abundant

A community with an H’ = 0 would have only one species

Human disturbance is a major threat to diversity because it can be frequent and or intense

The structure of a plant combined with its growth dynamics determines its life-form

When calculating the species diversity using the Shannon-Wiener index, the proportion of the i^th species is multiplied by the natural log of the proportion of the i^th species.

Based on Tilman’s work in 1977, the ratio of essential nutrients in communities can determine whether two species can coexist or exclude each other

In aquatic ecosystems, plant and algal diversity decline with increasing nutrient availability

The plot of a lognormal distribution would be bell shaped

MacArthur (1958) found that warbler diversity was correlated with foliage height

Very high levels of disturbance will reduce species diversity because few species will be able to survive the frequent and intense disturbances

Lilleskov and his colleagues found that acid-tolerant ectomycorrhizal fungi are dominant when soil nitrogen levels are high and the pH is low

Based on several surveys by Blair in 2004, avian diversity was highest in areas with an intermediate level of disturbance

High plant diversity is often correlated with high animal diversity

Species of plants with a higher percent cover and species of forest birds with higher numbers of individuals are both uncommon

In abandoned agricultural fields, nutrients and moisture do not necessarily correlate with each other creating habitat heterogeneity leading to greater plant diversity

The highest rates of species diversity found among boulders in the intertidal zone were found in areas of intermediate disturbance

By studying plant life-forms, scientists can reduce the number of species they are studying to better understand the community structure

Prairie dogs increase species diversity by creating a patchy environment with an intermediate level of disturbance

In the Park Grass Experiment, the rank-abundance curves have become steeper indicating a loss of species diversity

Worldwide urbanization has led to a homogenization of the global biota

Increases in land use intensity has led to the spread of already widespread and non-native birds species

Smaller boulders experience a higher frequency of disturbance, from this it could be predicted that species diversity would be lower on these boulders

Which community would have the highest species diversity? A community with high species richness and an abundance curve with the lowest slope

In 1980, George Sugihara proposed that the lognormal distribution of species in a community could be explained by species dividing the niches in a community

Prairie dogs create an intermediate level of disturbance that increases species diversity by allowing good colonizers and good competitors to coexist

Stream invertebrates that eat or “shred” terrestrial plant material would belong to the same guild

Nutrients in a lake such as nitrates, silicates and other nutrients can vary independently of each other over small spatial scales

In a community with very low species evenness, one would expect to encounter the same species many times before finding additional species

If two communities had the same species richness, but the rank-abundance curve for community A was much steeper than community B, then community B has a higher species diversity

Avian diversity has been found to be highest at golf courses

Under conditions of low nitrate availability, Lieskov found that fungal communities are comprised of species specialized in nitrogen uptake

Increases in land use intensity has led to a decrease in woodland bird species

Which community would have the higher species diversity? A community with 20 species with high species evenness

Varying nutrient levels in a lake creates environmental complexity leading to higher phytoplankton diversity

Animal diversity in terrestrial communities is positively correlated with plant diversity

Some ecosystems have many thousands of species, making it difficult to study the contribution of each species to the functioning of a community. Therefore, scientists may study the effects of groups of organisms on community structure by placing them into guilds

In temperate grasslands, plant diversity is highest where prairie dogs create a patchy environment

Based on Figure 16.16 illustrating the effect of fertilizing and plant diversity, it can be seen that plant diversity has decreased over time due to fertilizer use

The activities of prairie dogs help to increase plant diversity by creating bare patches of ground that facilitate colonization

A group of organisms that exploit resources in a similar way is termed a guild

In 1975, Robert May proposed that the lognormal distribution of species in a community could be explained as a statistical explanation based on many random variables

Based on Tilman’s 1977 work, two similar species of diatoms can coexist when the ratio of silicate to phosphate is low

When sampling species richness in a community, the common species will typically be found in small samples

Tilman demonstrated that Asterionella can exclude Cyclotella when the ratio of silicate to phosphate is high