The subject that covers everything related to the study of plant species is called botany. It is the responsibility of botanists to study and work for the conservation and preservation of the plant species. The subject that covers every concept related to the animal species is called zoology and zoologists take on the task to study, conserve and preserve animal species. As a whole, the subject that covers all concepts related to living organisms is called biology or life sciences. There are even subtopics related to the main topics that people also specialize in. For example, microbiology is a  study of microscopic organisms(organisms that cannot be observed through naked eyes).