3.Variation of entire systematic families

The study of a large number of genera within individual systematic families gave them the opportunity to discover the general trend in the variation, mandatory for all branches of the family.

Lets take the most studied family - Gramineae and dwell primarily on the basic types of division of labor and the different kinds of cereals on the variety. All cereals, if you look at the racial composition, divided by the density of the inflorescence. Millet is known to be divided into branchy, more closed, slumped and coms. In exactly the same share of sorghum - Andropogon. Oats divided by odnogrivye forms a dense inflorescence with short internodes and branches and bushy, subdivided according to the degree looseness (Schlafrispe, Steifrispe). Oats division essentially corresponds to the division into grades in millet and sorghum.

Spiked cereals all fall into ryhlokolosye, plotnokolosye and intermediate density. And in rye, and wheat, and barley, we have clearly marked differences in the density of inflorescence. Maize varieties are also divided by density clearly cob. Varieties of rice can also be divided according to the density of the inflorescence. Prairie grasses examined in terms of racial composition as Festuca pratensis, Phleum pratense, Bromus inermis, Dactylis glomerata, Agropyrum repens, etc., all can be divided according to the looseness of the inflorescence.

In general, the family of cereal is the division into filmy and hull-less forms, is the forms of grain, tightly enclosed in or flowering glumes, and grain, easy-release of cheshui.Takie forms are known in wheat, barley, rye, corn, millet, sorghum, foxtail.

By coloring the mature flower and glumes in cereals are five basic colors: white, yellow, red, gray and black sludge dark brown. These forms are set in wheat, barley, oats Riha, rice, millet, sorghum, goat grass, wheat grass, foxtail and other genera.

4.Phenotype and genotype variation

Harland has shown that different types of cotton, showing striking homologous series based on morphological and physiological characteristics, while at the same time, for the genes, in particular modifier genes, may be different.

On the probability of genetic differences in the similarity of the phenotype of individual traits are the facts polyploidy, doubling, quadrupling the chromosomes, particularly frequent in plants (wheat, oats, roses, poppies). It is possible that the nature of polyploidy causes polymer characteristics.

Thus, phenotypic study is the first approach, one that must go to genetic research.

Based on the striking similarity in the phenotypic variability of species within the same genus or related genera, due to the unity of the evolutionary process, we can assume that they have a common set of genes, along with the specific species and genera. A large number of factors points to the similarity of the major genes in closely related species and related genera. Mutations in family types and labor are generally in the same direction. Morgan, Bridges, Stertevent, Weinstein and Muller set it for different kinds of fruit flies, Babcock - for species of walnut, De Vries, Geytts, Stomps, etc. - in different species of evening primrose. Different species of rodents have identical genes (at least in appearance and behavior effect). Genetically most studied homologous genes in Drosophila melanogaster and D. simulans. In this case, to prove by crossing and study the localization of genes in the chromosomes of both species the presence of at least 26 homologous genes arranged in the same corresponding chromosomes [Sturtevant, 1929]. This is the most developed example of genetic variation in the homology of two close species. For other types of Drosophila, because of the difficulties of crossing until just set homology of individual genes.

Combining mutations in related plants and animals, can notice a lot of similar types of mutations.

The process of splitting on wheat chromosome hybridization differently in different combinations of species reveals many parallelisms, the occurrence of similar forms: narrow-leaved and broad-leaved, the appearance of the forms with branched spikes develop spines on glumes, the appearance of dwarfs as well as giants, albinos. These correctness can not be just random, parallel. They indicate the general nature of the genetic effects.