Answer :
Final answer:
Keystone species are essential to maintaining ecosystem diversity and structure, as their removal can lead to drastic ecological changes. In contrast, species like clams, while significant, do not exert similar regulatory effects on their ecosystems. Therefore, a species qualifies as a keystone when it has a major impact on the ecosystem's structure and population dynamics.
Explanation:
Understanding Keystone Species
A keystone species is defined as a species whose presence and role within an ecosystem have a disproportionately large impact on the structure and dynamics of that ecosystem.
These species are crucial for maintaining the biodiversity of their environments, and their absence can lead to significant and often detrimental changes. For example, apex predators like sea stars (e.g., Pisaster ochraceus) play a vital role in controlling the populations of their prey, such as mussels and sea urchins. If sea stars are removed from a coral reef community, the populations of mussels and sea urchins can grow uncontrollably, which can then lead to the decline of various other species and ultimately damage the overall structure and diversity of the ecosystem.
On the other hand, not all species affect their ecosystem to the same extent. For instance, clams, although they are primary consumers, do not exert the same regulatory influence on their ecosystem as keystone species do. If clams were to go extinct, their primary food source, phytoplankton, might increase, but this change would not have the explosive ecological repercussions seen with the removal of a keystone species. Thus, a keystone species must have a significant impact on multiple levels of the food web and on the overall ecosystem functionality.
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