Question 1

Biotic resistance will be effective as a control on invasive species in cases where the native species

Accepted Answer

A)  are weak predators or competitors. 
B)  are strong predators or competitors. 
C)  can evade the invading species. 
D)  can commandeer all available resources. 
E)  are in different taxonomic groups than the invaders.

Question 2

The Shannon index of species diversity is calculated using this equation:  Habitat A has a total of 100 birds, with the following numbers of individuals per species: 20, 25, 20, 15, and 20.Habitat B also has 100 birds, with the following numbers of individuals per species: 80, 5, 5, 5, and 5.What is the Shannon index for habitat B?

Accepted Answer

A)  0 
B)  1.60 
C)  0.78 
D)  F1F1F1S1F1F1F100.78 
E)  0.32

Question 3

Several woodpecker families inhabited dead trees, or snags, in a large backyard.They fed on many kinds of insects in the homeowner's garden.In an effort to "clean up" the backyard, the owner removed the snags.Having lost their nesting sites, the woodpecker families moved to a nearby woodland community, where they both nested and fed.There was a sudden, large boom in insect populations feeding on the garden plants.Based on this information, what is the best description of the interaction, and its strength, between the interactor species (woodpeckers) and the target species (insects)?

Accepted Answer

A)  Strong positive interaction 
B)  Strong negative interaction 
C)  Weak positive interaction 
D)  Weak negative interaction 
E)  No interaction

Question 4

A person trying to define an ecological community should remember that communities

Accepted Answer

A)  cannot be studied on the basis of their biomass. 
B)  do not always have clear-cut boundaries. 
C)  are always similar in size. 
D)  cannot be studied on the basis of energy distribution. 
E)  always have approximately the same number of species.

Question 5

In the ocean, phytoplankton are tiny floating algae and similar organisms, comprising many species, that carry out photosynthesis.Based on these characteristics, a community ecologist would most likely place all ocean phytoplankton into which subset of a community?

Accepted Answer

A)  Population 
B)  Taxonomic group 
C)  Food (trophic) web 
D)  Functional group 
E)  Interaction web

Question 6

There are often low levels of herbicides in agricultural soils and on the leaves and flowers of orchard trees.They are meant to kill weeds rather than insects, and levels are very low, but they may cause physiological changes in insect pollinators, making them weaker, with lower reproductive rates, and less effective at pollinating.These effects suggest that pesticides in orchards act as a _______ to pollinators.

Accepted Answer

A)  disturbance 
B)  stress 
C)  disease 
D)  competitor 
E)  stimulant

Question 7

High species diversity, considered a positive attribute of a community, is measured by both species richness and species evenness.How would higher species evenness likely act as a positive factor in the community?

Accepted Answer

A)  There would be fewer rare species; thus, there would be more individuals of each species, which could lower extinction risk. 
B)  There would be more rare species; thus, more species would remain in the community and fewer extinctions would occur. 
C)  There would be more total species present; thus, the food web would have more links. 
D)  There would be fewer total species present but more similar numbers of each, thus making cross-species reproduction easier. 
E)  There would be an overall lower species diversity, because species richness is more important in diversity than species evenness.

Question 8

As climate change continues, various species (including dolphins, robins, and finches) are now found in the Arctic, a place where they have not been seen before.What factor is likely responsible for the northern movement of these species?

Accepted Answer

A)  Rising temperatures 
B)  Competition with southern species 
C)  Decreasing temperatures 
D)  Changes in animals' ability to migrate 
E)  Changes in animals' ability to withstand cold

Question 9

A non-native marine mollusk is becoming established in a new environment.In the first years after it arrives, the temperature of the water gradually becomes warmer.Which response to the warming temperature might help the mollusk colonize its new environment?

Accepted Answer

A)  Decreased survival of young 
B)  Increased stress level 
C)  Decreased growth rate 
D)  Earlier age of reproduction, leading to increased reproductive rate 
E)  Higher metabolism, leading to greater need for food

Question 10

A species of fish is accidentally introduced into a habitat far from its home.Which factor would most likely prevent this species from becoming established in its new habitat?

Accepted Answer

A)  A much higher temperature than in its former habitat 
B)  The presence of several food species 
C)  Lack of predators 
D)  Stable levels of temperature and salinity 
E)  High species diversity in the new habitat

Question 11

A farmer decides to let a field that has been under cultivation revert back to natural prairie.The field is surrounded by other agricultural crop fields.The developing prairie may receive input of species from all of the following sources except

Accepted Answer

A)  seeds carried in on animal fur. 
B)  seeds brought in by birds from the area. 
C)  seeds brought in by wind and rain. 
D)  species living outside the regional species pool. 
E)  small mammals moving in from nearby fields or edges.

Question 12

During secondary succession, detritivores and decomposers are often among the most important early colonizers.What do these species do to initiate and advance succession?

Accepted Answer

A)  They are facilitators that release nutrients and improve soil for the first colonizing plants. 
B)  They are facilitators that enable the immediate colonization of large, perennial plants such as trees. 
C)  They are inhibitors that prevent the emergence of "weedy" plants, thus preventing them from competing with plants more adapted to the environment. 
D)  They are inhibitors that cause the rapid death and breakdown of early colonizers, allowing later colonizers to become established more quickly. 
E)  They are both facilitators and inhibitors, facilitating the colonization of plants adapted to that environment and inhibiting those less adapted.

Question 13

Species able to recolonize the Mount St.Helens area after the volcanic eruption in 1980 had to pass through several "filters" to become established in the ravaged area.What was the most immediate requirement of these species before they could become established?

Accepted Answer

A)  They had to withstand environmental conditions in the area. 
B)  They had to successfully interact with other species already in the area. 
C)  They had to be part of the regional species pool surrounding the area. 
D)  They had to build up large enough populations to remain viable. 
E)  They had to be able to leave the area in case of another eruption.

Question 14

Beavers cut trees and dam streams.This changes the structure of the ecosystem and alters the distribution and abundance of species in the area.Because of these activities, beavers are described as _______.

Accepted Answer

The answer of Beavers cut trees and dam streams.This changes...

Question 15

Which phrase best describes an ecological community, based on the theoretical definition?

Accepted Answer

A)  All field mice in a local grassland 
B)  All animals in a local grassland 
C)  All living organisms in a local grassland 
D)  All living organisms in all grasslands 
E)  All living organisms and all abiotic factors in a local grassland

Question 16

What is the most likely impact of adding a new (non-native) species to a community?

Accepted Answer

A)  All species in a community have equivalent impacts; this species simply adds one more impact. 
B)  It will affect only the species it eats or that eat it. 
C)  It will cause direct or indirect effects on many, if not all, species in the community. 
D)  It will only affect the other species in its own trophic level. 
E)  It will greatly increase the stability of the community.

Question 17

The turkey vulture, which feeds on relatively large dead animals, is considered a scavenger rather than a detritivore.What is the distinction?

Accepted Answer

A)  Detritivores feed on living, rather than dead, material. 
B)  Detritivores feed on the waste products and dead bodies of small organisms rather than larger dead organisms. 
C)  Detritivores feed only on plant material, scavengers only on animal material. 
D)  Detritivores break down material in aquatic ecosystems, scavengers in terrestrial ecosystems. 
E)  Detritivores do not return nutrients to the ecosystem; scavengers do return nutrients.

Question 18

Animals were instrumental in helping recolonize during primary succession after the eruption of Mount St.Helens.Based on scientists' observations, those animals most able to help in the early recolonization were those that could

Accepted Answer

A)  travel over the top of the pumice and ash. 
B)  burrow under the pumice and ash. 
C)  travel quickly to the area because they were large. 
D)  wait until the area formed new soil before settling there. 
E)  live for extended periods without food or water.

Question 19

Robins eat earthworms, but they also eat a variety of insects and berries.In a food web, the robin would be considered a(n)

Accepted Answer

A)  producer. 
B)  herbivore. 
C)  carnivore. 
D)  omnivore. 
E)  detritivore.

Question 20

When defining the concept of a community, ecologists today recognize that communities

Accepted Answer

A)  must have a precise number of species. 
B)  must extend over a relatively large geographic area. 
C)  do not always have easily recognizable boundaries. 
D)  always have precise, well-delineated boundaries. 
E)  only consist of species that spend the entire year inside community boundaries.

Exam 56: Communities