How to survive some weaker species in harsh environmental conditions? For their survival, their genes have a built-in adaptation mechanism, that is, changes in their properties under the influence of 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 wildlife are endless. It is interesting to understand how adaptation works.
Variability in biology. Types of variability
In official science there is such a thing as variability. It determines how an adult organism will develop and what signs it will acquire in the process of its development. Volatility as a whole is the ability of an organism to acquire new properties.
Distinguish between genetic and non-genetic variability. Non-genetic does not affect the genetic 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 another way, the latter is also called epigenetic variability.
Ontogenetic variability
An individual organism is formed in stages. During each stage, various environmental factors affect it. Indeed, any living creature cannot develop in isolation. And as a result of the influence of various factors, the body acquires new features.
Ontogenetic variation is at the intersection of genetic variation and non-genetic. In another way, it is also called epigenetic variability. Why is that? This type of variability differs from others in that new traits appear both as a result of established genetic programs, and at the same time because of environmental factors. Without such programs, nature would doom many living things to extinction.
The concept of ontogenesis
What is ontogenesis? This concept is one of the main ones in the biology course. To better understand what is ontogenetic variation, you need to know about the process of ontogenesis. In fact, scientists have identified the type of variability based on this very process.
Ontogenesis is a process of development from the moment of conception to birth. It is easy to follow this process on the example of butterfly development. Initially, a caterpillar is born (Fig. 1), a chrysalis is formed from it (Fig. 2, 3), which is also a life cycle. And an adult individual, a butterfly, flies out of the pupa. Ontogenesis is also characteristic of plants.
Everything that happens with a zygote (a fertilized egg) before the completion of the formation of an animal or person can be studied and analyzed.
Examples in nature
Based on the foregoing, the causes of ontogenetic variability are environmental conditions and genotype features. Genotype - as a formula that governs all changes.
How does a genotype regulate variability? The genotype of an individual regulates the work of certain genes, which should be "included" in a certain period of development. It is not the trait itself that is inherited by the specific organism, but the type of reaction to a certain environmental impact. This is the law of nature, which holds the key to understanding such a process as ontogenetic variability. Examples of such variability can be found in different countries and on different continents. Such variability is characteristic of animals, and insects, and the vegetable kingdom.
Let us trace the change in color and shape of the skin of the Andean toad, living in Ecuador. Its transformation during the period of ontogenesis is a classical “formula” of ontogenetic variability in nature.
A small toad does not have tubercles along the body; an adult individual, as we see, has growths on its sides. The color of the skin of the toad changes to copper-brown; and the color of the iris of bright red becomes copper-orange.
Value of variability
The significance of ontogenetic variability for wildlife is, first of all, the adaptation of each individual. The better it is, the greater the viability of the species in the environment. Another meaning of variability is the diversity of phenotypes. Each individual has, thanks to variability, its own individual characteristics.
Thanks to improved adaptation, the whole species is evolving. Although, of course, these changes are very slow.