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.

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.

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 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.

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

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.

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.

We know that a female has only X-chromosome in all her gametes and a male has X- chromosome as well as Y-chromosomes in male gametes. If a sperm carrying X-chromosome fertilises an egg cell which carries X-chromosome, then the zygote formed will have XX combination of sex chromosome due to which the child born will be a girl. If sperm carrying Y-chromosome fertilises an egg cell which carries X-chromosome, in the zygote formed will have XY combination of sex chromosome due to which the child born will be a boy or male.

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.

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].

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.

The main secondary sexual characteristics in females or girls are: i)Development of breasts in girls. ii)Hips broaden and become more curved and prominent in girls. iii)A shrill voice or high-pitched voice in girls. The secondary sexual characteristics in girls are produced by the female sex hormone called “estrogen” made in ovaries.

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

At puberty, the voice box (or larynx) begins to grow in boys as well as in girls. The growth of voice box in boys is much more than the growth of voice box in girls. Due to this, the voice box in boys becomes much bigger than the voice box in girls. This means that the grown-up boys have a bigger voice box in their throat whereas grown up girls have a smaller voice box in their throats.