Class 8 Science Chapter 10 MCQ

AIDS causing virus can be easily passed from an infected person to another person through: i) Sharing of syringes for blood transfusion, taking drugs etc. ii) Sexual contact iii) From infected mother to foetus It is not spread through an insect vector (such as insect bite) or through casual contact (such as sharing food, comb etc).

For metamorphosis of tadpoles, iodine should be present in water. This is because metamorphosis is brought about by thyroxine hormone that required the presence of iodine for its production by thyroid gland.

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.

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.

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.

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.

Development of breasts are related to girls or women not in boys. Rest of all, are the secondary sexual characters present in male at the time of puberty.

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”.

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

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.

In vertebrate anatomy, the pituitary gland, or hypophysis, is one piece and an endocrine gland, about the size of a pea and weighing 0.5 grams (0.018 oz) in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. Pituitary gland is called master gland because many of the hormones which it secrets control the functioning of other endocrine glands in the body.

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.

Here, present height of boy = 125 cm Percentage of full height = 78 Full height of boy = Present height of boy / Percentage of full height x 100 = 125 / 78 x 100 = 160.25 cm

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