Secondary Sexual character

The secondary sexual characters are the features which distinguish the individuals from both Sexe S of same a Espèce but, unlike the primary education sexual characters which are the sexual organs, they do not take part directly in the reproductive Système. The principal evolutionary theories to explain the appearance of such bodies rest on the idea that the secondary sexual characters are the object of a pressure of sexual Sélection intra-sex: at the time of the bridal parade, the individuals of the same sex are in competition to couple itself with an individual of the opposed sex, that (or that) which takes the advantage on its rivals is that (or that) which presents the secondary sexual characters gravitational for the partner or who allow him to take a lead in his rivals. That explains in particular why these characters appear in general at the time of sexual maturity (i.e the Puberté at the man).

In the mankind

The principal secondary sexual characters of the mankind are:

Formation of the secondary sexual characters

Sexual differentiation starts at the time of the Gestation, when the Gonade S are formed. The differences appear in the constitution of the girls and the boys only at the time of the Puberté, with the increase in the sex hormones.

At the individuals of male sex, the Testostérone induces the growth of the Pénis, and indirectly, (via the Androstanolone, that of the Prostate). The female oestradiol and the other hormones generate the formation of the Sein S at the woman. It should be noted that this process also depends on the rates of sex hormones at the fetal stage. Thus, the rate of Androgène S to which the fetus or the newborn is subjected will modulate the capacity of the fabric mammaire to answer the estrogens at the time of the Adolescence.

Behavioral secondary sexual characters

In any rigor, the secondary sexual characters are not limited to the anatomical characteristics which differentiate male and females of the same species but they include also the differences in physiology or the behavior (for example, the manufacture of nests in the shape of arbor by the garden birds male or dance of the male Pigeon) belong to the sexual Dimorphisme specific to the species. The Comportement is indeed a milked phenotypical: just like certain anatomical attributes are coded genetically (in the Génotype), certain behaviors dimorphic or not (for example, the bridal parade, but also the construction of the Nid or the Peur of Prédateur S) have a genetic base and are thus subjected to the sexual Natural selection and/or . The dimorphic behaviors are thus a case among others of secondary sexual characters. Recent work thus showed that it was possible, by handling the épissage of a single Gène in the fly female Drosophile, to induce a lasting behavior of bridal parade which those are put then, just like males, to court the other females.

References

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