Read the following passage and answer the items that follow. Your answers to these items should be based on the passage only.
Invasions of exotic species into new geographic areas sometimes occur naturally and without human agency. However, human actions have increased this trickle to a flood. Human caused introductions may occur either accidentally as a consequence of human transport, or intentionally but illegally to serve some private purpose or legitimately to procure some hoped-for public benefit by bringing a pest under control, producing new agricultural products new agricultural products or providing novel recreational opportunities. Many introduced species are assimilated into communities without much obvious effect. However, some have been responsible for dramatic changes to native species and natural communities. For example, the accidental introduction of the brown tree snake Boigairregularis into Guam, an island in the Pacific, has through nest predation reduced 10 endemic forest bird species to the point of extinction.
One of the major reasons for the world’s great biodiversity is the occurrence of centers of endemism so that similar habitats in different parts of the world are occupied by different groups of species that happen to have evolved there. If every species naturally had access to everywhere on the globe, we might expect a relatively small number of successful species to become dominant in each biome. The extent to which this homogenization can happen naturally is restricted by the limited powers of dispersal. By virtue of the transport opportunities offered by humans, these barriers have been breached by an ever-increasing number of exotic species. The effects of introductions have been to convert a hugely diverse range of local community compositions into something much more homogeneous. It would be wrong, however, to conclude that introducing species to a region will inevitably cause a decline in species richness there. For example, there are numerous species of plants, invertebrates and vertebrates found in continental Europe but absent from the British Isles (many because they have so far failed to recolonize after the last glaciations). Their introduction would be likely to significant detrimental effect noted above arises where aggressive species provide a novel challenge to endemic biotas ill-equipped to deal with them.
With reference to the passage, which of the following statements is correct?
Statement (d) is correct because statements (a), (b), and (c) present generalizations that are not fully supported or are directly contradicted by the information provided in the passage.
Option (a): The passage explicitly states, "It would be wrong, however, to conclude that introducing species to a region will inevitably cause a decline in species richness there." It further elaborates that some introductions, such as certain species from continental Europe to the British Isles, could potentially enrich local biotas. Therefore, the assertion that introduction of exotic species always leads to reduced biodiversity is incorrect.
Option (b): The passage indicates that while some introduced species have been responsible for "dramatic changes to native species and natural communities," it also notes that "Many introduced species are assimilated into communities without much obvious effect." This contradicts the claim that exotic species introduced by humans have always greatly altered native ecosystems.
Option (c): The passage explains that human actions have significantly increased the rate of homogenization by breaching natural dispersal barriers. However, it also acknowledges that homogenization can occur naturally, though restricted by "limited powers of dispersal." The statement that "Man is the only reason" for this conversion is therefore inaccurate, as natural processes also contribute, albeit at a slower pace.