Questions: Which of these BEST explains what would happen if pisaster starfish were wiped out from an intertidal zone? If pisaster starfish were wiped out, the ocean ecosystem would not change. If pisaster starfish were wiped out, mussels would overpopulate leading to impacts on other species. If pisaster starfish were wiped out, all mussel populations would die off with them.

The answer is the second one: If pisaster starfish were wiped out, mussels would overpopulate leading to impacts on other species.

Explanation for each option:

1. If pisaster starfish were wiped out, the ocean ecosystem would not change.
   This option is incorrect. Pisaster starfish are considered a keystone species in intertidal zones. Their presence helps maintain the balance of the ecosystem by preying on mussels. Without them, the ecosystem would likely experience significant changes.

2. If pisaster starfish were wiped out, mussels would overpopulate leading to impacts on other species.
   This option is correct. Pisaster starfish help control the population of mussels. Without them, mussels could overpopulate, which would lead to competition for space and resources, negatively affecting other species in the ecosystem.

3. If pisaster starfish were wiped out, all mussel populations would die off with them.
   This option is incorrect. The absence of pisaster starfish would not cause mussel populations to die off; rather, it would likely lead to their overpopulation due to the lack of predation.

In summary, the removal of pisaster starfish would disrupt the balance of the ecosystem, primarily by allowing mussel populations to grow unchecked, which would have cascading effects on other species.