Key Terms

Index species: Index species are used as a reference point to indicate relative placement in an ecosystem. For the tidepools, index species indicate your zonal location ie: splash, upper, middle, or lower zone.

Keystone predator: A keystone predator may prevent a particular prey species from overrunning an ecosystem. Locally sea stars perform this function by preying on mussels and other shellfish that have few natural predators. If the sea star is removed from the ecosystem, the mussel population could increase uncontrollably, driving out other species.

Diversity: For this lab, think of this as the total number of species. The total number of species generally goes up in areas of low stress and down in areas of high stress. This is not always true but is a good “rule of thumb”.