Ontogenetic variability. Causes and significance

How to survive some weaker species in difficult natural conditions? For their survival, a mechanism of adaptation is integrated in their genes, that is, changes in their properties under the influence of the forces of nature, such as air temperature, wind, sun.

The genetic program determines the formation of a butterfly from a pupa and the development of adult fish from a small egg. During this long development, all endogenous and exogenous factors will be reflected in the phenotype of the individual.

This is ontogenetic variability. Its examples in living nature are endless. It is interesting to understand how the adaptation works.

Variability in biology. Types of variability

In official science there is such a thing as variability. It determines how the adult organism will develop and what features it will acquire in the course of its development. Variability in general is the ability of the oraganism to acquire new properties.

There are genetic and non-genetic variability. Non-genetic does not affect the gene structure. Changes occur only within the normal range of the reaction. That is, the phenotype changes as much as the genotype allows it. Non-genetic variability is modification and ontogenetic. In a different way, the latter is also called epigenetic variability.

Ontogenetic variability

The individual organism is formed in stages. During each stage, various environmental factors affect it. After all, any living being can not develop in isolation. And as a result of the influence of certain factors, the body acquires new signs.

Ontogenetic variability is at the intersection of genetic variability and non-genetic variability. In another way, it is called epigenetic variability. Why is that? This kind of variability differs from the others in that new signs appear both as a result of the laid-down genetic programs, and at the same time because of the external characteristics. Without such programs, nature would doom many living creatures to extinction.

The concept of ontogeny

What is ontogeny? This concept is one of the main ones in the course of biology. To better understand what ontogenetic variability is, one must know about the process of ontogeny. In fact, scientists have identified the kind of variability based on this particular process.

Ontogeny is the process of development from conception to birth. It is easy to follow this process with the example of butterfly development. Initially, a caterpillar is born (Figure 1), a pupa is formed from it (Figures 2, 3), which is also a cycle of life. And from the chrysalis a grown-up individual, a butterfly, flies out. Ontogeny is also characteristic of plants.

Everything that happens with a zygote (a fertilized egg) until the formation of an animal or human is completed can be studied and analyzed.

Examples in nature

The causes of ontogenetic variability, based on the foregoing, are the environmental conditions and the characteristics of the genotype. The genotype is like a formula that regulates all changes.

How does the genotype regulate variability? The genotype of the individual regulates the work of certain genes, which must "turn on" in a certain period of development. Inherited by a particular organism is not the symptom itself, but the type of reaction to some effect of the habitat. This is the law of nature, which holds the key to understanding such a process as ontogenetic variability. Examples of such variability will be found in different countries and on different continents. Such variability is characteristic of animals, insects, and vegetable kingdoms.

Let us trace the change in the color and shape of the skin of the Andean toad living in Ecuador. Its transformation in the period of ontogenesis is the classical "formula" of ontogenetic variability in nature.

The small toad has no tubercles along the body, the adult specimen, as we see, has accretions on the sides. The toad's skin color changes to copper-brown; And the color of the iris of the eye from bright red becomes copper-orange.

Value of variability

The significance of ontogenetic variability for living nature is, first of all, the adaptation of each individual. The better it is, the greater the viability of the species in environmental conditions. Another value of variability is the diversity of phenotypes. Each individual has, due to its variability, its own individual characteristics.

Thanks to the improved adaptation, the whole species evolves. Although, of course, these changes are very slow.