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ScienceClass 8CBSE

Name the female hormone produced by ovaries that helps in development of mammary glands

Estrogen is the female hormone produced by ovaries that helps in development of mammary glands.

ScienceClass 8CBSE

Name the hormone that is released by testes at the onset of puberty.

Testosterone is the hormone that is released by testes at the onset of puberty

ScienceClass 8CBSE

Give a suitable word for each of the following statements. (a) The site which responds to a hormone. (b) Name of a gland which transports secretions through ducts. (c) Chemicals which control changes at adolescence stage. (d) It marks the beginning of reproductive period.

Target site Sweat glands/salivary glands/oil glands (any one) Hormones Puberty

ScienceClass 8CBSE

Complete the following sentences. (a) In females, the uterine wall thickens to receive the . (b) Endocrine glands release hormones directly into for transportation to the . (c) The sex hormones, and estrogen are responsible for the development of characters. (d) Release of sex hormones is under the control of a hormone secreted from the .

In females, the uterine wall thickens to receive the fertilized Endocrine glands release hormones directly into bloodstream for transportation to the target site. The sex hormones, Testosterone, estrogen and estrogen are responsible for the development of secondary sexual Release of sex hormones is under the control of a hormone secreted from the pituitary gland.

ScienceClass 8CBSE

Unscramble the underlined words in the following sentences. (a) Reproductive life of a woman lasts from hacreemn to spauoemen. (b) The development of a caterpillar to an adult butterfly is termed as poommertaissh. (c) The overgrowth of sumselc in xalnyr leads to the hoarse voice in adolescent boys. (d) Dannalier helps the body to adjust and fight the stress.

menarche, menopause metamorphosis muscles, larynx Adrenalin

ScienceClass 8CBSE

1. Structures present in a cell which is responsible for determination of the sex of a baby is (a) cytoplasm (b) cell membrane (c) nucleus chromosome

Answer is d (d) chromosome Explanation: 23rd set of chromosome which is called as sex chromosome determines the sex of the child. If 23red set of chromosome is XX baby will be female and if sex chromosome is XY then the baby will be a boy.

ScienceClass 8CBSE

The most conspicuous visible change that occurs in boys during puberty is: (a) development in voice box. (b) increase in height. (c) production of sperms. (d) increased sweating.

Answer is (b) increase in height. Explanation: Most conspicuous change during puberty is the sudden increase in height. At this time the long bones, that is, the bones of the arms and the legs elongate and make a person tall.

ScienceClass 8CBSE

For the metamorphosis of tadpoles which of the following elements must be available in water? (a) chlorine (b) carbon (c) sulphur iodine

Soln: Answer is (d) iodine Explanation: Metamorphosis is brought by a hormone called as thyroxine. Thyroid gland needs Iodine to secrete Thyroxine. Hence Iodine should be present in water for the metamorphosis of tadpoles.

ScienceClass 8CBSE

Given below are events that lead to pregnancy and development of embryo. i)Fertilization of egg ii)Maturation of egg iii)Release of egg iv) Embedding of embryo in thickened uterine wall. Which of the following options gives the correct order of sequence in which they occur? (a) i, ii, iii, iv, (b) ii, i, iii, iv (c) i, iv, ii, iii ii, iii, i, iv

Answer is (d) ii, iii, i, iv Explanation: Sequence of events are as follows . Maturation of egg after puberty Release of egg cell Fertilization of egg by sperm to form zygote Repeated division of zygote to form embryo Embyro gets embed in the wall of uterus for further

ScienceClass 8CBSE

AIDS can spread from an infected person to another person through (a) sharing food (b) blood transfusion (c) sharing comb a mosquito bite

Answer is (b) blood transfusion Explanation: AIDS can be transmitted from infected person by following means Sharing needles and syringes By sexual means through exchange of From infected mother to From infected mother to baby through breast

ScienceClass 8CBSE

The belief that the mother is completely responsible for the sex of the child is wrong because the child (a) gets sex chromosome only from the mother. (b) develops in the body of the mother. (c) gets one sex chromosome from the mother and the other from the father. gets sex chromosome only from the father

Answer is (c) gets one sex chromosome from the mother and the other from the father. Explanation: Mother has XX in their 23rd chromosome set. Mather always donates X to the offspring. Father has XY chromosome on the 23rd set. If father donates X child will be female. If Father donates Y then child will be male. Hence it is the father who is responsible for the sex of the child.

ScienceClass 8CBSE

It is much easier to burst an inflated balloon with a needle than by a finger. Explain.

Pressure exerted on an inflated balloon by the needle will be more as it has a smaller area of contact compared to the finger. This larger pressure pierces the surface of the balloon easily which will make the balloon burst.

ScienceClass 8CBSE

Two women are of the same weight. One wears sandals with pointed heels while the other wears sandals with flat soles. Which one would feel more comfortable while walking on a sandy beach? Give reasons for your answer.

Womens height are same and they apply same weight when they walk. But women wearing sandal withflat heel will be more comfortable while walking on sandy beach. This is because flat soles have larger area compared to the sandals with pointed heels. Also pressure exerted by the pointed heels will be more compared to that with sandals having flat soles. This pressure will make the sandals with pointed soled sink in the sand which will make difficult to walk on sand.

ScienceClass 8CBSE

It is difficult to cut cloth using a pair of scissors with blunt blades. Explain.

Blunt blade has larger area than shard edged blades. Because of this, blunt blade produces a low pressure which makes it difficult to cut the cloth. Whereas in sharp blade surface area is much is very less which increase the pressure produced. This makes the cutting of cloth easier with sharp blades.

ScienceClass 8CBSE

An archer shoots an arrow in the air horizontally. However, after moving some distance, the arrow falls to the ground. Name the initial force that sets the arrow in motion. Explain why the arrow ultimately falls down.

Archer puts muscular force to stretch the string. This will change the shape of the arrow. When the string is released arrow regains its original position which give it the initial force to set the motion. Because of gravitational from it come down towards after some time.

ScienceClass 8CBSE

A man is pushing a cart down a slope. Suddenly the cart starts moving faster and he wants to slow it down. What should he do?

He should apply a force to pull the cart up the slope.

ScienceClass 8CBSE

Fruits detached from a tree fall down due to force of gravity. We know that a force arises due to interaction between two objects. Name the objects interacting in this case.

Answer is earth and fruits

ScienceClass 8CBSE

Two thermocol balls held close to each other move away from each other. When they are released, name the force which might be responsible for this phenomenon. Explain.

Answer is electrostatic force. The balls have similar charges. They move away due to repulsion between similar charges.

ScienceClass 8CBSE

Two persons are applying forces on two opposite sides of a moving cart. The cart still moves with the same speed in the same direction. What do you infer about the magnitudes and direction of the forces applied.

Force applied is of equal magnitude in opposite direction hence the cart moves with the same speed in the same direction.

ScienceClass 8CBSE

A chapati maker is a machine which converts balls of dough into chapati’s. What effect of force comes into play in this process?

Force works on dough to convert it to chapati.

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