Exam 20: Communities of Organisms

The information presented in the figure below strongly suggests that the ________ is a keystone species in Yellowstone National Park.

Clown fish have evolved to live safely between the stinging tentacles of certain sea anemones.The fish receive protection from predators,whereas anemone receive some food from the fish.This relationship is an example of

Human cells contain mitochondria,which are responsible for processing the energy needed by the cells.The ancestors of mitochondria may once have been free-living prokaryotes.If mitochondria were still considered to be separate organisms within human cells,which of the following would best describe a human's relationship with them?