"cells use different processes at different times to provide an organism with the energy that it needs. spirulina is an autotrophic bacteria that can be found in freshwater and marine environments. which process takes place in the cells of spirulina that does not occur in the cells of a human?

This could be the answer you are looking for Spirulina are photoautotrophs meaning they are photosynthetic. That being said they perform photosynthesis  very simple.

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms