Correct Option (1)
The passage explicitly states that human actions influence biodiversity through various means. Statement 1 is correct because the passage mentions human-caused introductions occurring "intentionally but illegally to serve some private purpose," which encompasses activities like smuggling live organisms. Statement 2 is also correct as the passage refers to introductions happening "accidentally as a consequence of human transport." The construction and use of highways are a primary form of human transport that facilitates the accidental dispersal of species.
Incorrect Options:
Statement 3 is incorrect. The passage does not suggest that human beings influence biodiversity by making ecosystems sensitive to prevent the entry of new species. On the contrary, it details how human actions increase the introduction of exotic species, often with detrimental effects on native ecosystems.
Statement 4 is incorrect. The passage highlights that many introduced species have been "responsible for dramatic changes to native species and natural communities." It provides examples where human-facilitated introductions have led to the decline and extinction of local species, indicating that humans often fail to prevent major impacts, or even cause them, rather than ensuring their absence.