Try to collect all the currently accepted meanings for the word species. Discuss with your teacher the meaning of species in case of higher plants and animals on one hand, and bacteria on the other hand?
In biological terms, species is the basic unit of taxonomy. It can be defined as a group of similar organisms capable of interbreeding freely among themselves under natural conditions to produce fertile offsprings.
Therefore, a group of similar individuals that are reproductively isolated from other groups of individuals forms a species.
Species can also be defined as a group of individuals that share the same gene pool.