Sexual dimorphism is the difference in the structure of female and male organisms of the same species. It is widespread among diclinous representatives of animals or plants, and is manifested in such physical characteristics of individuals:
- The size. Males differ from females in size, for example, in representatives of amphibians, females are larger.
- Hairline. For example, in a person it may be the presence of a beard in men.
- Color. For example, in birds - the color of the feathers.
- Skin covering. It is expressed in additional formations and secondary sexual characteristics. For example, deer horns or rooster crests.
- Teeth. In male mammals, for example, walruses or elephants, the fangs are slightly larger than in females.
Thus, sexual dimorphism can be called an indicator of polygamy (its level), and the more pronounced it is, the greater the difference in the contributions of women and men to the care of their offspring. Sometimes PD can manifest itself in such signs that reduce the viability of their owners. Thus, the bright plumage, loud singing or pungent smell of some birds often attract the attention of predators, which poses a danger to their life. This is most likely due not to natural selection, but to sexual selection.
Sexual dimorphism can be of several forms:
- Reproductive PD - is constant by gender, both primary and secondary, which are different for representatives of both sexes and are related to the reproduction process. This is a hormonal form of sexual dimorphism, the task of which is to create a program for both sexes.
- Modification of sexual dimorphism - is temporary and occurs due to changes in the female sex as a result of selection. In this case, new genes arise that have been tested in male DNA.
PD is considered as an interrelation of female and male qualities aimed at forming attraction to each other, which creates the need for physical and psychological reproduction of a person. Thus, it is aimed at reproducing through a generation, and at the genetic level, biological control is created and the most beneficial qualities for the individual are developed.
It should be said that sexual dimorphism is manifested in a large number of physiological, somatic and behavioral differences of individuals of different sexes. Thus, stabilizing selection acts through the female sex, while the male gender creates the possibility of evolutionary variability. Modern science provides a clear explanation for the existence of gender differences at each level of development of the body.
In animals, PD is characterized by differences in the structure of the copulatory organs or secondary sexual characteristics. It is customary to distinguish seasonal and permanent sexual dimorphism here. Moreover, the first does not depend on seasonal conditions.
Human sexual dimorphism is expressed in a stronger development of the skeleton and muscles, as well as the male hairline. The female breasts are more developed, 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 much more.
Thus, the appearance and development of sexual dimorphism in all organisms is determined by the influence of natural and sexual selections. At the same time, modern biology has many arguments in favor of the fact that PD is expressed not only in the structure and functioning of the genital organs, it also covers secondary, tertiary and distant from sexual functions signs that relate to somatic systems and their functions. It can be said that all these characteristics relate to all levels of the organization of matter, starting from the molecular level and ending with the body level.