Class 8 Science Chapter 7 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.

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.

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.

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.

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.

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

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.

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.

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.

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.

Pancreas secretes the hormone called insulin. The function of insulin hormone is to lower the blood sugar level or blood glucose level. Deficiency of insulin hormone in the body causes a disease known as diabetes. If due to some reason, pancreas do not produce and secretes sufficient amount of insulin into blood then the sugar level in the blood rises. That diabetic person are advised by doctors to take insulin, less sugar in their diet, doing regular exercise and taking medicines.

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.