Which one of the following criteria is necessary for natural selection to occur? a. individuals show no variation in fitness levels. b. individuals have the same adaptations. c. a struggle for existence is apparent. d. enough resources exist for individuals to survive and thrive.

Clara wrote the following hypothesis for an experiment about acidophilic bacteria. bacteria cells will stop dividing in a basic (alkaline) environment because of the high ph. which statement is the best way to restate the hypothesis so that it is more specific? growing acidophilic bacteria in some environments will cause the cells to stop dividing because of ph. if the ph of their environment is changed, acidophilic bacterial cell division will be affected. if the environment of acidophilic bacterial cells becomes alkaline, the bacteria will stop dividing. the more alkaline an environment, the less cell division will occur in bacteria.