It is understood from the passage that the science of botany _____ .

Protoplasm, which is the fundamental basis of life, is
constantly undergoing physical and chemical change.
Life, therefore, is the resultant of these constantly
occurring changes. There are two great groups into
which living things may be classed: plants and
animals. Both the plant and the animal kingdoms are
very extensive. It is customary, therefore, to regard the
science of life under two comprehensive heads,
namely, botany which is the study of plants, and
zoology which is the study of animals. Both subjects
are subdivided into various specialised sections.