Forms and types of variability

On the planet Earth there is a huge amountdifferent forms of life, and at the same time there are not even two identical animals or plants on it. Different species are very different from each other, but even among very similar at first sight individuals of one species, there are no two absolutely identical to each other.

And what is most surprising, all of the above is true not only for sexually reproducing beings, but also for those who reproduce vegetatively, and even for clones.

So what are the living organisms of the Earth obliged to dohis personality? The fact is that since its formation - it does not matter, in the form of a zygote or a daughter process - the body begins to change. And he changes his whole life - until his death. This property of all living things was called variability.

However, variability does not always follow the same program, and therefore, as it was studied, scientists identified types of variability.

Thus, variability can be either individual (occurring with one creature) or group (occurring with the whole group). The first is the most common.

Also in a separate type is the geographicalvariability, the distinctive feature of which is the fact that changes with the essence occur under the influence of external factors of a certain territory.

Types of variability are divided by degreetransformation: if it is complete, radical, then this is qualitative variability, and if the transformation is only partial, incomplete, then this is quantitative variability.

If a living creature is affected by certainexternal factors provoking the transformation of characteristics, then this is directed variability, and if the transformation occurs spontaneously, then this is non-directional variability. In addition, there is also ontogenetic variability, which is the changes that occur throughout the development and life of the organism.

Despite the fact that there are so many optionspossible transformation of characteristics characteristic of the being, far from all the qualities acquired by him are transferred to his descendants. Therefore, the following types of variability are distinguished: hereditary and non-hereditary (modification).

However, this does not stop there. It is hereditary and non-hereditary varieties of variability are divided into subspecies. These subspecies differ in a whole complex of features and properties. And they are called, for convenience, forms.

So, the following forms of variability are distinguished: modification and genotypic. The modification, also called phenotypic, is manifested by the fact that different phenotypes change under the influence of the environment of different individuals of the same species. The changes received by organisms are individual, not inherited.

For example, if the dandelion root is dividedhalf and plant in different conditions (one half in the mountains, the second in the lowland), then by the time the plants reach puberty, it will be quite obvious that the plant phenotype is radically different. The dandelion grown in the mountains will be short, its leaves and flower will not be large. But the plant grown in the valley, on the contrary, will be high, and its leaves - large. And if the descendants of these plants grow in the same conditions, then there will be no difference between them.

The main significance of this modification lies in the possibility of adapting the living organism to the current habitat.

Genotypic variability is cardinallydiffers from the modification, because as a result it changes not the phenotype, but the genotype, and the new, acquired attribute is inherited. Genotypic variability is divided into two subspecies: a combination and a mutation (mutation).

Combinative variability is the occurrence ofdescendant of new properties due to any new combinations of genes from his parents. So, for example, when crossing sweet pea with white flowers in their offspring, the flowers may have a purple color.

Mutation is a sudden, but at the same time stable change in the genetic material of the organism itself, transmitted to the descendants. Mutations are individual and directed.