Which Is Not S Econdary Sex Gland In Animals

Features that occur in an organism at sexual maturity

A peacock displays his long, colored tail, an example of secondary sex activity characteristics.

Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals.^{[1] [ii]} These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a species,^[3] but unlike the sex organs (principal sexual practice characteristics), are not directly part of the reproductive organisation.^[4] Secondary sexual practice characteristics are believed to be the product of sexual selection for traits which display fitness, giving an organism an advantage over its rivals in courtship and in aggressive interactions.^[v]

Secondary sex characteristics include, for example, the manes of male lions,^[ii] the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes. These characteristics are believed to exist produced by a positive feedback loop known every bit the Fisherian runaway produced by the secondary characteristic in i sexual activity and the desire for that characteristic in the other sexual practice. Male person birds and fish of many species take brighter coloration or other external ornaments. Differences in size between sexes are also considered secondary sexual characteristics.

In humans, visible secondary sex activity characteristics include enlarged breasts and widened hips of females, facial pilus and Adam's apples on males, and pubic hair on both.^{[4] [6]}

Evolutionary roots [edit]

A blood-red deer stag's antlers are secondary sexual characteristics.

Charles Darwin hypothesized that sexual selection, or competition within a species for mates, can explain observed differences betwixt sexes in many species.^{[7] [ better source needed ]}

Ronald Fisher, the English biologist, developed a number of ideas apropos secondary characteristics in his 1930 book The Genetical Theory of Natural Selection, including the concept of Fisherian runaway which postulates that the desire for a characteristic in females combined with that feature in males can create a positive feedback loop or delinquent where the feature becomes hugely amplified. The 1975 handicap principle extends this idea, stating that a peacock'south tail, for instance, displays fettle past beingness a useless impediment that is very hard to imitation. Some other of Fisher'south ideas is the sexy son hypothesis, whereby females volition want to have sons that possess the characteristic that they find sexually attractive in gild to maximize the number of grandchildren they produce.^[8] An culling hypothesis is that some of the genes that enable males to develop impressive ornaments or fighting ability may be correlated with fitness markers such as disease resistance or a more efficient metabolism. This thought is known as the proficient genes hypothesis.^{[ citation needed ]}

In not-man animals [edit]

Secondary sex characteristics in not-human animals include manes of male person lions^[ii] and long feathers of male person peafowl, the tusks of male narwhals, enlarged proboscises in male elephant seals and proboscis monkeys, the bright facial and rump coloration of male person mandrills, and horns in many goats and antelopes. ^[ix]

Biologists today distinguish between "male-to-male combat" and "mate choice", unremarkably female choice of male mates. Sexual characteristics due to combat are such things as antlers, horns, and greater size. Characteristics due to mate choice, often referred to as ornaments, include brighter plumage, coloration, and other features that have no immediate purpose for survival or gainsay.^{[ citation needed ]}

Male jumping spiders have visual patches of UV reflectance, which are ornamentations used to attract females.^[10]

In humans [edit]

Anatomical characteristics of the human male and female person

Sexual differentiation begins during gestation, when the gonads are formed. The general structure and shape of the torso and face, also as sexual practice hormone levels, are similar in preadolescent boys and girls. As puberty begins and sex hormone levels rise, differences announced, though some changes are similar in males and females. Male levels of testosterone directly induce the growth of the genitals, and indirectly (via dihydrotestosterone (DHT)) the prostate. Estradiol and other hormones cause breasts to develop in females. Yet, fetal or neonatal androgens may modulate later breast evolution past reducing the capacity of breast tissue to respond to later estrogen.^{[eleven] [12] [xiii]}

Underarm hair and pubic hair are usually considered secondary sexual practice characteristics,^[6] but they may also be considered non-secondary sex characteristics because they are features of both sexes following puberty.^[fourteen]

Females [edit]

In females, breasts are a manifestation of college levels of estrogen; estrogen likewise widens the pelvis and increases the corporeality of body fat in hips, thighs, buttocks, and breasts.^{[4] [half-dozen]} Estrogen also induces growth of the uterus, proliferation of the endometrium, and menstruum.^[iv] Female secondary sex characteristics include:

• Enlargement of breasts and erection of nipples.^{[4] [6]}
• Growth of body hair, most prominently underarm and pubic hair.^{[ii] [4] [6]}
• Widening of hips;^{[iv] [half dozen]} lower waist to hip ratio than adult males.^[xv]
• Elbows that hyperextend 5–8° more than than male person adults.^[16]
• Upper artillery approximately 2 cm longer, on boilerplate, for a given height.^[17]
• Labia minora, the inner lips of the vulva, may abound more prominent and undergo changes in color with the increased stimulation related to higher levels of estrogen.^[eighteen]

Males [edit]

The increased secretion of testosterone from the testes during puberty causes the male secondary sexual characteristics to be manifested.^[nineteen] In males, testosterone directly increases size and mass of muscles, song cords, and bones, deepening the voice, and changing the shape of the face up and skeleton.^[4] Converted into DHT in the skin, it accelerates growth of androgen-responsive facial and body hair but may slow and eventually stop the growth of head hair.^{[ citation needed ]} Taller stature is largely a result of afterward puberty and slower epiphyseal fusion.^{[ commendation needed ]} Male person secondary sex characteristics include:

• Growth of trunk hair, including underarm, abdominal, chest pilus and pubic hair.^{[two] [iv]}
• Growth of facial pilus.^[four]
• Enlargement of larynx (Adam's apple) and deepening of vocalisation.^{[four] [20]}
• Increased stature; adult males are taller than adult females, on boilerplate.^[4]
• Heavier skull and bone structure.^[iv]
• Increased muscle mass and force.^[iv]
• Broadening of shoulders and chest; shoulders wider than hips.^[21]
• Increased secretions of oil and sweat glands.^[20]

References [edit]

1. ^ Melmed S, Polonsky KS, Larsen PR, Kronenberg HM (2011). Williams Textbook of Endocrinology E-Book. Elsevier Wellness Sciences. p. 1054. ISBN978-1437736007.
2. ^ ^{a b c d e} Pack PE (2016). CliffsNotes AP Biology (5th ed.). Houghton Mifflin Harcourt. p. 219. ISBN978-0544784178.
3. ^ Norris Do, Lopez KH (2010). Hormones and Reproduction of Vertebrates, Book 1. Academic Printing. p. 87. ISBN978-0080958095.
4. ^ ^{a b c d e f thou h i j chiliad l m n} Bjorklund DF, Blasi CH (2011). Child and Boyish Development: An Integrated Approach. Cengage Learning. pp. 152–153. ISBN978-1133168379.
5. ^ Campbell B (2017). Human being Evolution: An Introduction to Man's Adaptations. Routledge. pp. 392–393. ISBN978-1351514415.
6. ^ ^{a b c d e f} Rizzo DC (2015). Fundamentals of Anatomy and Physiology. Cengage Learning. pp. 483–484. ISBN978-1305445420.
7. ^ Darwin, C. (1871) The Descent of Man and Selection in Relation to Sex John Murray, London
8. ^ Weatherhead PJ, Robertson RJ (February 1979). "Offspring quality and the polygyny threshold: "The sexy son hypothesis"". American Naturalist. 113 (2): 201–208. doi:10.1086/283379. S2CID 85283084.
9. ^ "Primary and Secondary Sex Characteristics". Retrieved 14 Baronial 2020.
10. ^ Lim, Matthew 50. 1000., and Daiqin Li. "Courting and Male-Male Agonistic Behaviour of Comsophasis Umbratica Simon, an Ornate Jumping Spider (Araneae: Salticidae)." The Raffles Bulletin of Zoology (2004): 52(2): 435-448. National Academy of Singapore. 20 September 2015
11. ^ G. Raspé (22 October 2013). Hormones and Embryonic Evolution: Advances in the Biosciences. Elsevier Science. pp. 32–. ISBN978-1-4831-5171-7. The first genetic male child with a defect in 3β-hydroxy-Δ5-steroid oxidoreductase to have reached puberty has been reported to have a high level of 3β-hydroxy-A5 steroid excretion, hypospadias at birth, table salt-wasting, and a history of 2 siblings with congenital adrenal hyperplasia and cryptic ballocks [33]. Although at puberty he has signs of virilization, he has developed pronounced gynecomastia. Thus, this boy demonstrates that breast development may occur in postpubertal males if the programing of the pubertal sexual activity differentiation of the mammary gland anlagen is disturbed past an enzyme defect which causes a failure of fetal testicular testosterone product. This observation is completely consistent with the findings in the experimental models [11, 32].
12. ^ Neumann F, Elger Westward (March 1967). "Steroidal stimulation of mammary glands in prenatally feminized male rats". Eur. J. Pharmacol. 1 (2): 120–3. doi:10.1016/0014-2999(67)90048-9. PMID 6070056. When administered to gravid rats during pregnancy an anti-androgenic steroid [cyproterone acetate] induced development of nipples in male fetuses. These nipples and associated glandular tissues develop subsequently birth as in normal female animals. Progestin-estrogen treatment of developed, castrated feminized males produced stimulation of the glandular tissue similar to that seen later on treatment of castrated female animals. In castrated male rats this treatment produces little glandular proliferation. Information technology is concluded that androgens commonly prevent the development of nipples and extensive formation of mammary tissue in male fetuses.
13. ^ Rajendran KG, Shah PN, Dubey AK, Bagli NP (1977). "Mammary gland differentiation in developed male rat--effect of prenatal exposure to cyproterone acetate". Endocr Res Commun. 4 (v): 267–74. doi:ten.3109/07435807709052946. PMID 608453. Breast tissue of adult male Holtzman rats exposed to cyproterone acetate during embryonic differentiation showed presence of specific estradiol receptor proteins and C-19 steroid aromatase. We reported similar findings in gynecomastia in man. It is therefore proposed that gynecomastia probably results from failure of adequate testosterone action on the breast primordia during embryonic differentiation.
14. ^ Sherwood Fifty (2011). Fundamentals of Human Physiology. Cengage Learning. p. 578. ISBN978-0840062253.
15. ^ Osculation, David (March 15, 2019). Evolutionary Psychology: The New Scientific discipline of the Mind (Sixth ed.). Routledge. p. 290. ISBN9780429590061.
16. ^ Amis AA, Miller JH (December 1982). "The elbow". Clinics in Rheumatic Diseases. 8 (3): 571–93. doi:x.1016/S0307-742X(21)00409-iv. PMID 7184689.
17. ^ Manwatching: A Field Guide to Human Behaviour, 1977, Desmond Morris
18. ^ Lloyd, Jillian (May 2005). "Female genital appearance: 'normality' unfolds". British Journal of Obstetrics and Gynaecology. 12 (five): 643–646. CiteSeerXten.1.1.585.1427. doi:x.1111/j.1471-0528.2004.00517.x. PMID 15842291. S2CID 17818072.
19. ^ Van de Graaff & Play a trick on 1989, p. 933-4. sfn error: no target: CITEREFVan_de_GraaffFox1989 (help)
20. ^ ^{a b} Sexual reproduction Archived 2009-02-08 at the Wayback Auto
21. ^ "Secondary Characteristics". hu-berlin.de. Archived from the original on 2011-09-27.

Source: https://en.wikipedia.org/wiki/Secondary_sex_characteristic

Posted by: bustosgrosen.blogspot.com

Share this post