Final answer:
Predation by sea stars results in an altered community structure on rocky shores due to their role as a keystone species. Their predatory behavior controls prey population and maintains ecosystem balance, which supports biodiversity.
Step-by-step explanation:
Predation by sea stars on rocky shores ultimately results in altered community structure. This is because sea stars, acting as a keystone species, significantly influence the population dynamics of their prey, such as mussels and sea urchins, which leads to significant effects on the entire marine community. For instance, if the sea stars were to be removed, the unchecked growth of their prey could eventually outcompete other species, leading to a decrease in biodiversity and a simpler community structure. Conversely, their predation helps maintain ecosystem balance, allowing for a variety of species to thrive.
Community-level interactions can be greatly impacted by changes in predator-prey dynamics. An example of altered community structure is seen with the introduction of oyster reefs, which change the substrate and increase habitat complexity. This leads to higher species richness and an alteration in the infauna and epifauna populations. Similarly, removal of predators like sea stars can have consequences on marine ecosystems. As such, this predatory role helps control the abundance of prey species, which in turn sustains a diverse array of life forms within the ecosystem.