Class 8 Science Chapter 7 MCQ

The child gets one sex chromosome from the mother and one from the father. The mother has XX combination and always contributes an X-chromosome. It is the sperm of father which determines the sex of the child. This is because half of the sperms have X-chromosome and another half have Y-chromosome.

The most visible change during puberty in boys is sudden increase in height. At this time, the long bones elongate and make a person tall.

The sex of baby is determined by the type of sex chromosomes present in the fertilised egg from which the baby develops. There are two types of sex chromosomes-X and Y. A female has only two X-chromosomes, i.e., XX, whereas a male has one X and one Y-chromosome, i.e., XY combination.

Adrenaline is called stress hormone which is secreted from adrenal glands at the time of stress. It helps the body to face the emergency situation or flight away from it.

The sex hormones, testosterone and oestrogen are responsible for the development of sexual characters. Secondary sexual characters are visible characters which help us to differentiate between two sexes i.e., male and female. The growth of secondary sexual characters is controlled by sex hormones i.e., testosterone in males produced by testes and oestrogen in females produced by ovaries.

Here, all the statements are correct. Hence, your answer will be option [D].

Menarche is the beginning of the reproductive life of a girl or woman. The first menstruation or menstrual flow begins at puberty when the girl or woman is around 10 to 12 years of age. The first occurrence of menstruation at puberty is called “Menarche”. In other words, menarche is the time from which a girl or woman become capable of having a baby. Menstruation stops permanently when a woman reaches the age of about 45 to 50 years. With the permanent stoppage of menstruation, a woman lost her ability to be children. The permanent stoppage of menstruation in a woman is called “Menopause”.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

A female (women or mother) has only X-chromosomes in all her gametes called “eggs or ova”. A male (man or father) has X-chromosomes as well as Y-chromosomes in male gametes called “sperms”.

We know that the deficiency of thyroxine hormone causes a disease known as goitre. The main symptom of goitre disease is that the neck of the person suffering from goitre appears to be swollen. People are advised to take iodised salt for cooking food so as to prevent goitre disease. Iodised salt contains appropriate amount of iodine compounds such as potassium iodide which can provide all the iodine needed by thyroid gland to make sufficient thyroxine hormone for our body.

AIDS stand for Acquired Immune Deficiency Syndrome. AIDS is dangerous disease which is caused by a virus called HIV. HIV stands for Human Immunodeficiency Virus. This virus is present in the blood of AIDS patient.

The diet which contains the correct amount of each constituent (such as carbohydrates, fats, proteins, vitamins and minerals) sufficient for the normal growth and development of the body and keep a person healthy is called a balanced diet. Our Indian meal of roti (or rice), pulses (or dal), and vegetables is a balanced diet. Remember, for infants (or small babies) mother’s milk provides all the necessary nourishment which they need.

Adrenals are endocrine glands. The adrenal glands produce adrenaline hormone. Pituitary is endocrine glands. The pituitary gland secretes a number of hormones such as testes, ovaries, thyroid gland and adrenal gland to secrete their hormones. Rest of all are correctly match.

Drugs are very powerful chemical substances and should be used only under a doctor’s supervision. Adolescent boys and girls should avoid drugs to maintain physical, mental and social well-being which are necessary to live a purposeful, fruitful and satisfying life in this world. There are many harmful effects of taking drugs so we should avoid these.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

The hormones play an important role in initiating the reproductive function of adolescence at the time of puberty. The rise in the level of sex hormones is responsible for the changes in the bodies of adolescent boys and girls at puberty. The testes make male sex hormone called “testosterone” and the ovaries make female sex hormone called “estrogen”. The production of these sex hormones is under the control of another hormone called “gonadotropic hormone” secreted by pituitary gland.

Once a female attains puberty, she menstruates every month. An egg or ovum is produced by the ovary every month. If this egg is not fertilized by a sperm, then the unfertilized egg and endometrium is removed as waste through menstruation. This cycle continues until the female gets pregnant. When a female is pregnant, she does not menstruate. Menstruation resumes after delivery and continues every month absent a pregnancy until the female attains menopause. There are two conditions which can lead to menstruation in a 21-year-old woman during ovulation. These are: (i) Blocked oviduct and, (ii) Sperms not available for fertilization.

Many young boys and girls get pimples and acne on the face during puberty. The pimples and acne are formed due to the increased activity of sebaceous glands and sweat glands present in the skin. The level of hormones in boys and girls rises too much at puberty. These hormones stimulate the glands and sweat glands present in skin and secrete more oil and sweat. The accumulation of oil, sweat and dead skin cells blocked the tiny pore in the skin of the face. Bacteria grows in the mixture of oils, sweat and dead skin cells in the blocked skin pores causing the swelling and redness of skin which leads to the formation of pimples.

Here, all the statements are correct. Hence, your answer will be option [D].