Humans are advanced organisms of the Animal kingdom and are sexually dimorphic like many other multicellular organisms. Sexually dimorphic organisms appear physically distinctive though both of them belong to the same species. The main purpose of sexual dimorphism is the physical attraction between the opposite sex. Colorful plumage in many bird species and antlers in reindeers are some examples of sexually dimorphic features in the animal kingdom.
Human life has different growth phases and reproductive maturity is obtained by the mediation of a number of hormones. The reproductive system is comprised of organs primarily designed to support reproduction and continue their species. Even though humans are born with testes and uterus (male and female reproductive organs), reproduction is possible only after a certain age when the individual attains maturity.
Adolescence is the transition phase of childhood to adulthood and grants a number of physiological, physical, behavioral, and psychological changes in an individual.
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Secondary sexual characteristics are a set of features that mark members of one sex distinct from members of another sex in the same species. They mark the physical appearance of an individual and develop with age or develop in the breeding season if the organisms are seasonal breeders.
They are not directly involved in reproduction while they are essential for sexual display. Most commonly females produce offsprings and male individuals attract females for sex. Secondary sexual characteristics allow physical attraction between organisms of the opposite sex. In humans, females with large breasts, and rounded hips, and males with facial hair and voice changes are some secondary sexual characteristics. These features develop while childhood is set on into adulthood through adolescence.
Humans grow from childhood to adulthood and reach reproductive maturity by passing through a transition phase called adolescence. This transition to adulthood is accompanied by a surge of hormonal changes which make an individual reproductively mature. Adolescence starts at 10 years and extends till 19 years after which an individual is considered an adult. Children entering adolescence are considered teenagers or adolescents. This period is driven by hormonal changes impacting their physique and helping them attain reproductive capacity. Most noted is the physical development but the brain also undergoes a growth spurt which has much more impact on their emotional and psychological status.
An individual undergoes a lot of changes with respect to the physique, cognitive thinking, and emotional connections. It is a fact that many adolescents experience bigger changes in their behavior. Adolescence is divided into three stages based on age.
Early adolescence (age 10-13 years).
At this age, most individuals grow in height and weight. Puberty hits females early than males of the same age. Females experience growth in breasts and hips. Males experience deepening of their voice and growth of the penis and testicles.
Middle adolescence (age 14-17 years).
At this age, physical growth in terms of weight and height stops in females while the males continue their growth. Menstruation becomes regular in females. Both males and females experience facial acne.
Late adolescence (age 18-21 years).
During this age, most individuals experience slowed down physical growth. They already attained adult height. They experience more emotional stability than the middle adolescents.
After the age of late adolescence, individuals are considered adults. Adulthood marks them as reproductively functional individuals.
Adolescents become sexually mature and attain reproductive capacity through puberty. Sexual maturity is more related to primary sexual organs, however, there are a vast number of changes in the perspective of endocrinology contributing to gradual physical changes which are manifested as secondary sexual characteristics.
The gonadotrophin-releasing hormone is released from the brain and stimulates the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The FSH and LH act on gonads (ovaries and testes) to release sex hormones that are responsible for attaining sexual maturity.
The age of attaining puberty varies with gender. Females attain puberty a little early than males of the same age. Apart from gender, genetic factors, environment, stress, and nutrition also impact the age of puberty.
Secondary sexual characteristics are a result of hormonal actions. In males, testosterone from the testes is responsible for secondary sexual characteristics. Testosterone in turn is controlled by the hypothalamus and pituitary gland secretions. Secondary sexual characteristics in males include.
Presence of body hair (arms, chest, and pubic hair).
Facial hair as mustache and beard.
Deep voice due to enlargement of the larynx,.
Body musculature with widened upper body (chest).
Development of Adam's apple.
Secondary sexual characteristics in females are a result of the actions of estrogen. The female secondary sexual characteristics include −.
Growth of pubic and underarm hair
Enlargement of breasts
Rounded hips
Lighter upper body musculature
High pitch voice
Although puberty and adolescence are quite interrelated topics, there lie some differences between them.
Puberty is the stage where an individual attains reproductive maturity. It is brought about by hormones and is more concerned with sexual characters. The physical manifestation of gender is a result of puberty.
Adolescence is the transition period between childhood and adulthood. It is an overall transition in terms of physical, behavioral, and cognitive thinking. Adolescence deals with the emotional health of individuals along with secondary sexual characteristics.
Human beings are born with primary sexual organs (uterus in females and penis in males). All through childhood individuals experience growth in physical and psychological terms. In order to attain adulthood and become reproductively functional, humans pass through a transition phase called adolescence. Spanning from 10 years to 19 years, adolescence is a crucial phase that is packed up with growth, and social behavioral changes. Adulthood starts only after an individual reaches reproductive maturity through puberty, which is driven by a surge of hormones. The secondary sexual characteristics represent the sexuality of an individual and are not directly involved in reproduction. It is the role of primary sexual organs to carry on the process of reproduction.
Q1. Which hormones control secondary sexual characteristics?
Ans. Male sex hormone testosterone secreted from Leydig cells of testes is responsible for male secondary sexual characters. Female sex hormone estrogen secreted from ovaries is responsible for female secondary sexual characteristics. Secretion of estrogen and testosterone is regulated by follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland which is controlled by gonadotrophin-releasing hormone (GnRH) of the hypothalamus.
Q2. What is the relationship between puberty and fertility?
Ans. Attaining puberty makes an individual reproductively functional. The gonads start to produce spermatozoa and ova upon becoming reproductively active.
Q3. What is the reason for developing facial acne in adolescence?
Ans. Adolescents develop facial acne because of overactive oil glands as a result of hormonal changes.
Q4. Explain sexual dimorphism
Ans. Sexual dimorphism is the phenomenon where individuals of the same species exhibit different characteristics with respect to their sexuality. The two sexes show differences in physical appearance, and physiological patterns however, the differentiating characteristics are not directly involved in the reproduction process.
Q5. Give some examples of sexual dimorphism in the animal kingdom
Ans. Sexual dimorphism is common in the animal kingdom and might have evolved as a result of sexual selection.
Male lions are huge and physically different from the lioness.
Male Mandarin ducks are more attractive with bright bills and colorful feathers than female ducks.
The male peacock has a long bright colored feathery tail which is different from the female one.
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