Robert Paine Was the First Biologist to Use the Term

question 31

Multiple Choice

Robert Paine was the first biologist to use the term keystone species in the 1960s. He was studying food webs in the rocky, intertidal pools in the Pacific Northwest. At one of his study sites, the dominant organisms in the tidal pools were mussels, barnacles, whelks, and a species of starfish known as Pisaster ochraceus . To examine the relationship between these species, Paine set up an experiment. In one area, he removed all the starfish from the tidal pools, and in an adjacent area, he left the tidal pools as he found them. Prior to removing the starfish, he sampled all the organisms in each pool. After two months, he repeated this sampling. A summary of his results is illustrated in the graph below.

In Paine's study, the starfish are the top predators in this system and eat each of the other species mentioned. Whelks eat both mussels and barnacles, while both mussels and barnacles are filter feeders that feed on small particles in the water, including algae and other autotrophs. In terms of the number of organisms, you would expect __________ to have the highest number of individuals.

• A) mussels
• B) whelks
• C) starfish
• D) both whelks and starfish

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