Some of the earliest research on keystone species was conducted by robert t. paine, who actually coined the term keystone species. for over 25 years paine and his students removed pisaster ochraceus, a sea star, from tidal pools on the coast of washington. throughout his research, paine discovered that removal of this predator resulted in a) another predator moving in to replace the sea stars. b) a change in trophic levels, with only producers and herbivores present. c) mussels becoming the dominant species and crowding out all competitors. d) a shift in the ecosystem and a new keystone species becoming established.

Read the following scenario to answer the following question. over the past 60 years, many amphibian species have experienced significant population declines, and some species have become extinct. scientists suspected that local human activities such as the destruction of wetlands, regional pollution, and deforestation were the main reasons for these losses. however, research over the past 20 years reveals significant amphibian population declines in protected areas of the world, such as nature preserves and parks. these global declines suggest widespread problems including increased ultraviolet radiation, acid rain, and disease. in switzerland, for example, 14 of the 20 native amphibian species are threatened with extinction. when most populations of a wide-ranging amphibian species are lost and the few remaining populations are widely separated, we expect to see that a. the founder effect becomes increasingly important b. microevolution no longer occurs c. gene flow between populations is reduced d. artificial selection becomes a greater factor in microevolution

What do lava flows made of aa indicate about the type of volcanic eruption that occurred? a. the eruption was viscous. b. the eruption was pyroclastic. c. the eruption was explosive. d. the eruption was quite. !

Which of the following produces carbon dioxide? a. plants b. animals c. decomposers d. all of the above