Іn the article the modern scientific researches on building and development of key competencies in theory and practice of pedagogical science are analyzed. The peculiarities of the professional activity of the teacher of biology through the interrelation of his/her informative, developmental, orientation, mobilizing, constructive, communicative, and organizational and research functions are researched.The analysis of modern approaches in the preparation of the future teacher of biology made it possible to determine leading functions in the educational process of a secondary school: informative, developmental, orientation, mobilization, constructive, communicative, and organizational and research. All functions are interrelated; they complement and refine each other.A large number of researchers prove that the competency-based approach most completely reflects the modern processes in European countries.Taking into account the world experience and needs of the development of the Ukrainian school in the domestic pedagogy, three types of competencies characterizing the results of learning on the basis of a competency-based approach are recognized: key, interdisciplinary and knowledge of subject.The notion of "competency-based approach" refers to the orientation of the educational process on the building and development of the key (basic, main) and substantive competencies of the individual. The result of this process will be the formation of a general competence (professionalism) of a person, which is the integrity of key and substantive competencies, an integrated personality trait. Such a characteristic should be formed in the process of learning and contain knowledge, skills, attitudes, experience, values and behavioural models of personality.The competency-based approach takes special place in the process of building and development of competencies of the future specialist in the system of higher education. In the scientific sense, the concept of "approach" is interpreted as the starting point for forming the basis of research activity. The general idea of a competency-based approach is competence-oriented education, which aims at the complex of knowledge acquisition and methods of practical activity, through which a person successfully implements himself/herself in various fields of life. The most important specificity of the competency-based approach lies in the fact that not the "ready-made knowledge" transmitted by the teacher is assimilated, but "the conditions of the origin of this knowledge are traced".