单选题 Scientists formerly assumed that coral populations remained stable, dead polyps being replaced by now ones that build on the "skeletons" left behind. Recent investigations, however, reveal more dynamic processes. Whole sections of a colony may die and not be replaced. This process, known as partial colony mortality, is evident in a series of photographs over time, but often impossible to detect in site because "skeletons" bared by the death of overlying tissue are readily overgrown by other organisms or abraded by grazers. Partial mortality can produce fission the process of a large colony splitting apart into two or more adjacent colonies that presumably have identical genetic makeup. Subsequent lateral growth may unite these colonies in a process called fusion. As a consequence of these three processes, estimates of coral ages based on size are Partial mortality and fission, which reduce colony size, occur more frequently than fusion, and thus estimates of coral age based on colony size are probably far too low.

单选题 Which of the following best describes the organization of the passage?

单选题 The primary purpose of the passage is to______.

单选题 According to the passage, all of the following are confounding factors in determining the exact age of a coral colony EXCEPT______.