Food chains are usually short mainly because a) only a single species of herbivore feeds on each plant species. b) local extinction of a species causes the extinction of the other species in its food chain. c) most of the energy in a trophic level is lost as it passes to the next higher level. d) predator species are less diverse and less abundant than prey species. e) most producers are inedible.

Scientists are conducting a study on the effectiveness of a new drug on memory loss. they are giving some of the test subjects the new drug to find out if it improves their long-term memory. which are possible limitations of this study? check all that apply. a) test subjects may want to participate in additional experiments. b) test subjects may think they should be paid more. c) test subjects may get bored and want to quit early. d) test subjects may have to travel during the experiment. e) test subjects may have full-time jobs. this is multiple choice. you for the !