[Campbell Biology P.1233] According to Figure 52.20 and the accompanying text, what is the pr... | Practice Question

According to Figure 52.20 and the accompanying text, what is the primary conclusion regarding the effect of the long-spined sea urchin Centrostephanus rodgersii on seaweed distribution?

  • A: The presence of *C. rodgersii* significantly promotes the growth and spread of seaweed.
  • B: *C. rodgersii* has no discernible effect on seaweed distribution, as shown by the parallel lines in the graph.
  • C: The presence of *C. rodgersii* acts as a biotic factor limiting the distribution of seaweed.
  • D: Seaweed abundance is inversely related to *C. rodgersii* density only in shallow waters.

Explanation

Figure 52.20 clearly shows that when sea urchins were removed 'Urchins removed' line , seaweed cover increased dramatically compared to the control group where urchins were present 'Control urchins present ' line . This demonstrates that C. rodgersii limits the distribution and abundance of seaweed.