There are a huge number of people on planet Earth.different forms of life, and while it does not even have two identical animals or plants. Different species are very different from each other, but even among very similar at first glance 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-propagated creatures, but also for those who reproduce vegetatively, and even for clones.
So why do the living organisms of the Earth owe suchyour personality? The fact is that from the moment of its formation - it does not matter, in the form of a zygote or a child 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, the variability does not always proceed according to the same program, and therefore, as it is studied, the scientists identified the types of variability.
Thus, the variability can be either individual (occurring with one being) or group (occurring with the whole group). The first is the most common.
Also in a separate form is allocated geographicalvariability, a distinctive feature of which is the fact that changes with a creature occur under the influence of external factors of a certain territory.
The types of variability are divided according to the degreetransformations: if it is complete, radical, then it is qualitative variability, and if the transformation is only partial, incomplete, then it is quantitative variability.
If a living being is affected by certainexternal factors that trigger the transformation of signs, then this is directional variability, and if the transformation occurs spontaneously, then this is undirected variability. In addition, there is also an ontogenetic variability, which is a change occurring throughout the entire development and life of the organism.
Despite the fact that there are so many optionspossible transformation of the characteristics characteristic of the creature, not all of the qualities it acquired are passed on to its descendants. Therefore, the following types of variability are also distinguished: hereditary and non-hereditary (modification).
However, this does not end there.It is hereditary and non-hereditary types of variability that 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. Modification, also called phenotypic, is manifested in the fact that in different individuals of the same species, the phenotype changes under the influence of the environment. The changes obtained by the organisms are individual, not inherited.
For example, if dandelion root is dividedin half and plant in different conditions (one half - in the mountains, the second - in the valley), then by the time the plants reach puberty, it will be quite obvious that the plant phenotype is radically different. A dandelion grown in the mountains will be short, its leaves and flower will not be large. But the plant grown in the valley, by contrast, will be high, and its leaves - large. And if the descendants of these plants grow under the same conditions, there will be no difference between them.
The main value of such a modification is the ability of the living organism to adapt to the current habitat.
Genotypic variation dramaticallydiffers from the modification, because as a result it changes not the phenotype, but the genotype, and a new, acquired trait is inherited. Genotypic variation is divided into two subspecies: combinational and mutational (mutation).
Combinative variability is the occurrence ofa descendant of new properties due to any new combinations of genes in its parents. For example, when crossing sweet peas with white flowers at their descendant, the flowers may have a purple color.
Mutation is a sudden, but at the same time stable change of the very genetic material of the body, transmitted to descendants. Mutations are individual and directed.
