Natural selection: sexual dimorphism

Sexual dimorphism is the difference in the structure of female and male organisms of the same species. It is widely distributed among dioecious representatives of animals or plants, and manifests itself in such physical traits of individuals:

1. The size. Males differ from females in size, for example, in representatives of amphibian females larger.
2. Hair cover. For example, in humans, this can be the presence of a beard in men.
3. Colour. For example, in birds, the color of feathers.
4. Skin covering. It is expressed in additional formations and secondary sexual characteristics. For example, the horns of deer or the comb of cocks.
5. Teeth. In male mammals, for example, walrus or an elephant, the fangs are somewhat larger than in females.

Thus, sexual dimorphism can be called an indicator of polygamy (its level), and the more vividly it is expressed, the more differences in the contributions of the female and the male in caring for their offspring. Sometimes PD can manifest itself in such signs, which reduce the viability of their owners. So, bright plumage, loud singing or a sharp smell of some birds often attract the attention of predators, which poses a danger to their life. This is due, most likely, not by natural selection, but by sexual selection.

Sexual dimorphism occurs in several forms:

1. Reproductive PD - is a constant sex, both primary and secondary, which are different in both sexes and are related to the process of reproduction. This is a hormonal form of sexual dimorphism, the task of which is to compile a program for both sexes.
2. Modificational sexual dimorphism - is temporary and arises from changes in the female sex as a result of the selection action. In this case, new genes arise that have been tested in male DNA.

PDs are considered as an interrelation of female and masculine qualities aimed at the formation of attraction to each other, which creates the need for a person's physical and psychological reproduction. Thus, it is aimed at reproduction through the generation, and at the genetic level, the creation of biological control and the development of the most beneficial for the individual qualities.

It should be said that sexual dimorphism manifests itself in a large number of physiological, somatic and behavioral differences between individuals of different sexes. So, through the female sex there is a selection of stabilizing, male gender creates the possibility of evolutionary variability. Modern science provides a clear explanation for the presence of gender differences at each level of development of the organism.

In animals PD is characterized by differences in the structure of copulatory organs or secondary sexual characteristics. Here it is customary to single out seasonal and constant sexual dimorphism. The first one does not depend on seasonal conditions.

Sexual dimorphism of a person is expressed in a stronger development of the skeleton and musculature, as well as the hairline in the male sex. The female has more developed breast mammary gland, the width of the hips is also greater.

In plants PD is expressed in differences in the structure and size of the stems, the density of foliage, the structure of flowers and in many ways different.

Thus, the appearance and development of sexual dimorphism in all organisms is determined by the influence of natural and sexual selection. At the same time, modern biology has many arguments in support of the fact that PD is expressed not only in the structure and functioning of the genital organs, it also includes secondary, tertiary and genital-long features that relate to somatic systems and their functions. We can say that all these characteristics refer to all levels of organization of matter, from the molecular level to the organismic level.