The ontogenesis is the development of an individual being and differs from phylogenesis known as phylogenetic development. The concept of ontogenesis goes back to Ernst Haeckel. Both ontogenetic and phylogenetic considerations play a role in modern psychology and medicine.
Developmental biology and modern medicine usually consider the development of living organisms from the fertilized egg cell to the adult organism under the term ontogenesis.
The term ontogenesis comes from Ernst Haeckel, who first used it in the 19th century. In the meantime, ontogeny is associated with the development of an individual and is consequently opposed to phylogeny. Ontogeny deals with the history of the structural change of a particular unit.
In developmental psychology, ontogenesis stands for the psychological development of the individual. Biology understands this to mean the individual development of the body and deals with the development of an individual living being, which begins with the stage of the fertilized egg cell and ends in the adult living being. Step by step, the embryo develops organic structures that become full organs. In the individual organs, cells are organized in tissues that differentiate and specialize.
According to widespread opinion, ontogeny is closely related to phylogeny and often makes its features visible. On the basis of ontogeny, conclusions can be drawn about the phylogeny of living beings. For Ernst Haeckel, this was the basic biogenetic law.
The beginning of individual development belongs to ontogeny. This beginning is localized for the metazoa on the fertilized egg cell. The end of development and thus of ontogenesis is ultimately the death of the living being.
Multi-celled cells differ from single-celled cells. The mother cell of unicellular organisms goes into the daughter cells during reproduction. In contrast to multicellular cells, single-celled organisms have the potential to be immortal. Without death as the end point, the ontogeny of the individual living being still has a starting point, but no longer an end.In the case of unicellular organisms, the ontogenetic consideration of one living being from the time of reproduction overlaps with the ontogenetic consideration of the newly created living being.
Developmental biology and modern medicine usually consider the development of living organisms from the fertilized egg cell to the adult organism under the term ontogenesis. In the development of the individual being, according to widespread assumption, stages occur that can be compared with the stages of development of the tribe. The phylogenetic series of development are thus passed through in the ontogenesis of each individual of the species.
This theory is controversial today. The ontogenetic consideration today mainly includes the consideration of the cell differentiations in the embryo, which lead to the development of certain organs. The biological ontogenesis of multicellular cells is now considered in the phases of conception, blastogenesis, embryogenesis, fetogenesis, birth, infant phase, infant stage, juvenile phase, pubescence and adolescence as well as climacteric, senescence and death.
It is different in psychology. Freud worked out four phases for the development of the individual, which became part of the teachings on infantile sexuality. According to Freud, Granville Stanley Hall's psychogenetic constitution referred to the biogenetic constitution, referring to ethnology, just as Haeckel referred to tribal history.
Carl Gustav Jung used the term ontogenesis in connection with the individual and collective psyche. The latter is the inherited and supra-personal part of each individual soul and thus a product of the phylogeny that everyone goes through in ontogeny. The upper parts of mental functions are to be separated from this and form the individual part of the soul, which can be perceived by becoming conscious of the personal unconscious.
In psychology, ontogenesis can also correspond to the development or change of mental abilities and mental structures in the course of the individual life story.
Psychology recognizes ontogenetic reduction in the sense of a tracing of the state of health back to events in one's own life story as a psychotherapeutic method. For example, people react to traumatic events in different ways. On the basis of ontogenesis, a traumatic event can cause pathological changes in the mental state and thus mental illnesses in one person, while a second person does not react to the same event with the same changes in the psyche. Ultimately, all mental illnesses manifest themselves on an ontogenetic level and can hardly have a phylogenetic origin.
On the other hand, phylogenesis in the sense of common human development tendencies can favor certain diseases of the psyche. According to Haeckel's original theory, conclusions about phylogeny can be drawn on the basis of ontogenesis. Thus, in relation to ontogenetic disease developments, conclusions can be drawn about the phylogenetically determined tendencies of a species to certain diseases.
Just as this conclusion could be valid for physiological illnesses, it may also be valid for mental illnesses under certain circumstances. Modern pathology deals with both phylogenetic and ontogenetic considerations of certain diseases. If there is a phylogenetic basis for a certain disease, this disease automatically manifests itself more often ontogenetically than a disease without a phylogenetic basis.