What dramatically changes when Starfish are removed from the simulated system?
A. Acorn and Gooseneck Barnacle populations increase in size.
B. The Mussel population increases in size.
C. The Coral Weed population increases in size.
D. The system remains largely unchanged.
The Correct Answer and Explanation is:
The correct answer is: B. The Mussel population increases in size.
Explanation:
In a simulated ecosystem, organisms interact with each other in complex ways, creating a food web. Starfish, specifically the species Pisaster ochraceus, are often considered keystone predators, meaning their presence plays a critical role in maintaining the balance of the ecosystem. When starfish are removed from the system, it can dramatically alter the structure of the community, especially in intertidal zones.
Starfish are known to feed on mussels, acorn barnacles, and other organisms that populate the rocky shores. In particular, Pisaster starfish prey heavily on mussels, which are abundant in these habitats. By removing the starfish, the primary predation pressure on the mussels is eliminated, allowing mussel populations to increase in size. This phenomenon is often referred to as a trophic cascade, where the removal of a top predator leads to significant changes in the abundance of lower trophic levels.
In the absence of starfish, mussels can grow unchecked because they are no longer being consumed in significant numbers. This can result in the overcrowding of mussels on rocks, potentially outcompeting other species for space and resources. However, the primary immediate effect is the rapid increase in the mussel population, which would not be possible as long as the starfish are present.
Now, let’s consider the other options:
- A. Acorn and Gooseneck Barnacle populations increase in size. While barnacles are part of the intertidal ecosystem, their population size is more directly affected by other factors like competition for space or food. The absence of starfish may not directly lead to an increase in barnacle populations.
- C. The Coral Weed population increases in size. Coral weeds or algae are often grazed by herbivores or compete with other species for space, but this effect is less directly related to starfish predation.
- D. The system remains largely unchanged. This is incorrect because the removal of starfish does have significant impacts, especially on the mussel population.
In conclusion, the removal of starfish leads to a dramatic increase in mussel populations due to the lack of predation pressure, and this is a key example of how a keystone predator influences the balance of an ecosystem.