To determine whether one species blocks another out of an area, one

To determine whether one species blocks another out of an area, one approach is to infer assembly rules, which reconstruct the sequence in which species were added to an evolving community. For example, the presence of a plant species might support the establishment of a beetle that feeds on the plant, and a wasp that in turn parasitizes the beetle. Each of these species, like a puzzle piece, might block the entry of some competing species into the community. But whether a species holds an exclusive functional place cannot easily be identified by studying a community as an isolated unit; local communities are not isolated assemblages and are better thought of as members of a metacommunity of linked smaller ecosystems. Consequently, observing the existence of two functionally similar species in a particular community could reflect that there is room for both species in the assembly or that they really belong to what are mostly distinct, neighboring communities. For example, in a particular brackish coastal lagoon, the species scophtalmus rhombus and solea solea are not only both fish, but have comparable functional traits such as eye diameters, caudal fin aspect ratios, and length-to-body-depth ratios. This functional similarity could imply mutual exclusivity, but another possibility is that scophtalmus rhombus and solea solea occupy positions in the same community within the lagoon, perhaps because food is abundant or because they are less functionally similar than they appear; another is that they occupy exclusive positions in neighboring communities within that lagoon or the mouth of that lagoon to the coastal seas, and they fact that they have been found near each other reflects an exception rather than the rule.

1. The passage mentions which of the following as a factor that implies that scophtalmus rhombus and solea solea might not tend to coexist in the same ecosystem?

A. The degree to which they are functionally similar
B. The degree to which other animals within that ecosystem prey on both scophtalmus rhombus and solea solea
C. The fact that communities are not isolated entities and are better thought of as members of groups of ecosystems
D. The similarity of the ratio of the species' dorsal fin to body length
E. The degree to which prey are abundant in a particular ecosystem



2. Which of the following hypothetical experiments most clearly exemplifies the method of identifying species' roles that the author considers problematic?

A. The weevils in deciduous forest are counted across a series of ecosystems in order to determine whether they are blocking out other beetles.
B. A species of fish that is dominant in one marine ecosystem is introduced into another marine ecosystem to see whether the species will be dominant there.
C. Whether one woodpecker blocks another from occupying a particular ecosystem is determined based on the similarity or difference of their prey in that community.
D. A study is made to determine average levels of species diversity in communities in a particular type of climate, such as temperate forests.
E. Patterns of species extinction are studied in order to evaluate the effect of the climate changes on diversity in a particular tundra community.



3. Which of the following, if true, would most clearly support the statement presented in the last sentence of the passage?

A. As a species of small mammal becomes more abundant, it tends to have a larger effect on the community it inhabits, especially a megacommunity.
B. Two species of aphid that have identical diets tend not to coexist within the same ecosystem but may do so if prey is especially abundant.
C. Study of a marshland reveals that more species with functional similarities coexist within that ecosystem than had previously been supposed.
D. A species of bat is completely dependent on the insect populations within a community, and the ability of that insect population to exist depends on the presence of certain plant species.
E. Although two species of bird within a particular ecosystem hunt the same prey, one camouflages itself while hunting and the other does not.



4. The passage suggests which of the following about determining whether one species blocks another out of an area?

A. Such a determination can be made solely on the basis of functional characteristics, as long as neighboring communities are considered.
B. Such a determination must be made of an ecosystem considered with clearly defined boundaries.
C. Such a determination is likely to be less accurate for communities that contain more species of a given family.
D. Such a determination cannot be proved or disproved for two given species simply by finding them both within the same ecosystem.
E. Such a determination can best be made by observing the diet of species in succession, starting with plant life.