8th Class Science Human Reproduction Sex Determination

       Sex Determination

The sex of an individual is determined by the combination of sex chromosomes X and Y. If the chromosomal combination is XX, it results in female child. On the other hand, if it is XY, it results in male child. These chromosomes help in the exchange of genetic material.

              Puberty and Adolescence

At the age of adolescence, some major changes occur in boys and girls, in physic as well as, in behavior. Some of the changes seen in boys are, cracking of voice, cranky, growth of hair in armpit and genital areas, growth of body muscles and more importantly production of sperms and arousal of sexual feelings. On the other hand, in girls growing of breast, growth of hair in genital areas, onset of menstrual cycle and growth of body muscles are seen. They also show behavioral changes. While puberty covers the physical changes, adolescence deals with the mental changes and has been described as a 'psychosocial process characterized by mental and social growth, and often extending from puberty to the early 20 s and sometimes beyond.' These transformations in the girls are seen between the ages of 8 and 12 years, while in boys it is seen couple of years later. But still, there is no strict time frame for the onset of puberty.

             Behavior Changes

Most adolescents are uncomfortable and unconscious about their growing breasts and suddenly awkward limbs. They feel that the people are looking at them differently. Every pimple seems magnified a hundred times, and girls hunch overtryingto.concealtheirgrowing waist lines. To make matters worse, most parents are at a loss when faced with their children's budding sexuality. They cannot accept the fact that their 'babies' are talking and thinking about sex. As a result, adolescents are ecstatic one minute, irritable and moody the next. On one hand, they display a new-found maturity in keeping with their 'adult' status. On the other, they throw tantrums, that could rival a three-year-old.

Puberty and adolescence bring with them a lot of emotional baggage. People in their adolescent years feel as if they are in a twilight zone, hanging somewhere in between childhood and adulthood. As if they're sitting on an emotional seesaw, feeling 'up' one minute, down the next; feeling old on some days, and like a child on others. It is a difficult time, but it makes one feel better to think that everyone has gone through it.

            Endocrine System

The endocrine system is made up of a series of ductless glands that produce hormones. A number of glands that signal each other in sequence are usually referred as axis. Some of the endocrine glands are pituitary, thyroid and adrenal glands. The features of endocrine glands in general are, their ductless nature, their vascularity and usually, the presence of intracellular vacuoles or granules storing their hormones. On the other hand exocrine glands such as, salivary glands, sweat glands and the glands inside the gastrointestinal tract are less vascular and have ducts to store the hormones. The major endocrine glands founded in male and female are pineal gland, pituitary gland, thyroid gland, adrenal gland, pancreas, ovary, testis and thymus gland.

  Endocrine System  

            Cross Breeding

It is usually referred to an animal with purebred parents of two different breeds or varieties. It can also be defined as the breeding of animals of desired traits with the animals of other traits. The term is also used at times, to refer to a domestic animal of unknown ancestry, where the breed status of only one parent or grandparent is known, though the term "mixed breeding" is technically more accurate. The term outcross is used to describe a type of crossbreeding, used within a purebred breed to increase the genetic diversity within the breed, particularly when there is a need to avoid inbreeding.

         The new born baby will be a male or female depends on the type of the combination of sex chromosomes. The types of sex chromosomes present in human are X and Y. Which one of the following combination given below will give birth to a male child?

(a) XX

(b) XY

(c) XXX

(d) YY

(e) None of these

Answer: (b)

        There are two types of gland in our body, some are ductless and other is with duct. A number of gland that signals each other in a sequence are usually referred as:

(a) Endocrine

(b) Exocrine    

(c) Axis

(d) Vascularity

(e) None of these

Answer: (c)

Explanation

The glands which works in a sequence are referred as axis, while ductless gland are called endocrine and duct gland are called exocrine.