Pаine's experiments оn stаrfish remоvаl shоwed that a year after the starfish had been removed, the number of species decreased from 15 to eight, after three years the number went down to seven, and after another seven years it was almost all only mussels. In the control plots the number and diversity of species was basically unchanged. Which statement(s) best explain(s) these results? (Select all that apply)