CBSE Class 10 Science How Do Organisms Reproduce VBQs Set 07

These 21 value based and real-life questions for Class 10 Science, chapter How Do Organisms Reproduce, come with step-by-step answers, a simple-words summary and a teacher's note for each. They deal with HIV and AIDS awareness, female foeticide and the sex ratio, contraception and family planning, puberty, and everyday examples of vegetative propagation and fission.

Value Based and Competency Questions

Question 1. Rajeev, a sales executive in a MNC was not keeping well for a long time. He underwent a complete medical check-up and was diagnosed as HIV+. He was terminated on account of this condition. (i) To which category of disease does AIDS belong to? Give its causative organism. (ii) Do you think it was a right decision by the head of the company? Justify. (iii) What concern should the society show towards HIV+ individuals?
Answer:
(i) AIDS is a sexually transmitted disease (STD). Its causative organism is a virus, the HIV (Human Immunodeficiency Virus).
(ii) No, it was not right. HIV does not spread by shaking hands, working together or sharing a room with an infected person. It spreads by unprotected sex, infected blood or needles and from an infected mother to her child. So there is no reason to remove him from his job.
(iii) Society should treat HIV+ persons with a positive attitude, give them equal rights, proper care and treatment, and spread awareness about HIV and AIDS instead of isolating them.
In simple words: HIV does not spread by ordinary contact, so a person with HIV must not be treated unfairly.

Teacher's Note:
1. Mention the modes of spread to show that the firing was wrong.
2. Value to write: care and respect for HIV+ persons.

Question 2. On the notice board of ultrasound clinics it is generally stated: "Here prenatal sex determination and disclosure of sex (boy or girl before birth) of foetus is not done. It is prohibited and punishable under law." (a) List two advantages of imposing ban on prenatal sex determination. (b) What can students do to educate the society about the following? (i) The ill-effects of indiscriminate female foeticide. (ii) Adopting small family norms.
Answer:
(a) (i) It checks female foeticide. (ii) It helps to improve the sex ratio (female : male ratio) in the country.
(b)(i) Students can explain that female foeticide is reducing the number of girls drastically in some societies. For a healthy society the male-female ratio must stay almost equal, and reckless foeticide is making the child sex ratio decline at an alarming rate.
(b)(ii) They can explain that in a small family all the children can get good food, clothing, education and a healthy life, and that fewer children also keep the mother in good health.
In simple words: The law stops sex-selective abortion so that boys and girls stay in balance.

Teacher's Note:
1. Write two clear points for part (a).
2. In part (b) give practical ideas such as talks, posters and street plays.

Question 3. If you have to go in a village during AIDS prevention programme, what points will you explain to the villagers?
Answer:
1. AIDS is caused by the virus HIV, which weakens the immune system. It cannot yet be cured, so prevention is important.
2. It spreads through unprotected sexual contact, infected blood or needles and from an infected mother to the child. Condoms should be used in sexual contact.
3. Use disposable (sterilised) syringes and needles, and make sure blood used for transfusion is tested. Pregnant women should be checked.
4. It does not spread by touching, shaking hands or sharing food, so infected persons should not be avoided or ill-treated.
In simple words: Explain how AIDS spreads, how to prevent it and why patients deserve kindness.

Teacher's Note:
1. List the modes of spread and the matching precautions.
2. Include the message of no discrimination.

Question 4. Our government launches campaigns to provide information about AIDS prevention, testing and treatment by putting posters, conducting radio shows and using other agencies of advertisements. To which category of diseases AIDS belongs? Name and explain. What is its causative organism? Also give two more examples of such diseases.
Answer:
1. AIDS belongs to sexually transmitted diseases (STDs). These are diseases that spread by sexual contact with an infected person.
2. Its causative organism is a virus, HIV.
3. Two more examples of STDs are gonorrhoea and syphilis (both caused by bacteria).
In simple words: AIDS is an STD caused by the HIV virus; gonorrhoea and syphilis are other STDs.

Teacher's Note:
1. Define STD in one line.
2. Name the virus and two other STDs.

Question 5. A newly married couple wants to conceive as quickly as possible. What is the first sign of pregnancy shown by the woman?
Answer:
1. The first sign of pregnancy is the absence of menstruation (a missed period).
2. When the egg is fertilised and the embryo gets implanted, the thick lining of the uterus is needed to nourish it. It is not shed, so the monthly bleeding stops.
3. The couple should then consult a doctor to confirm the pregnancy.
In simple words: A missed period is the first sign of pregnancy.

Teacher's Note:
1. Explain why the lining is not shed.
2. A doctor's confirmation is the responsible step.

Question 6. How can people practice safe sex to avoid contracting an STD?
Answer:
1. By using a condom (barrier method) during sexual contact. It does not allow the semen and the body fluids to be exchanged.
2. This prevents STDs and also avoids unwanted pregnancy.
In simple words: A condom protects against STDs and unwanted pregnancy.

Teacher's Note:
1. Name the barrier method.
2. Add that other methods such as Copper-T do not protect against STDs.

Question 7. Mrs. Seghal's family was very happy after the birth of their second child. Her friend, Mrs. Raman, suggested her to undergo tubectomy. (A) What is tubectomy? (B) Why do you think Mrs. Raman gave her such a suggestion? (C) Can tubectomy prevent the spread of sexually transmitted diseases? (D) Give reason for your answer. Why is there a need of adopting contraceptive methods?
Answer:
(A) Tubectomy is a surgical method of birth control in females. A small portion of each oviduct is removed or tied, so the egg cannot reach the uterus and fertilisation and pregnancy do not occur.
(B) A small family is a happy family. With two children the parents can give good food, clothes and education to each child, and fewer pregnancies keep the mother healthy.
(C) No.
(D) Tubectomy does not put a physical barrier between the partners, so an infected person can still pass on an STD. Contraceptive methods are needed to avoid unwanted pregnancies, to control the birth rate and population, and (barrier methods) to avoid STDs.
In simple words: Tubectomy stops pregnancy, but only a condom also protects from STDs.

Teacher's Note:
1. Define tubectomy in one line.
2. Remember: tubectomy and vasectomy do not stop STDs.

Question 8. Like yeast, any organism which gets access to sufficient food and conducive living conditions, starts to reproduce and the population continues to grow. The same applies to humans as well. However, some adults may not be ready mentally, physically, socially, financially to reproduce at certain stages of life. Contraceptive options allow these individuals to wait or avoid reproduction. However, certain contraceptive options also have a short or long-term impact on the individual's ability to reproduce. Studies have shown that many women take anywhere from 2 to 15 menstrual cycles after stopping the contraceptive pills before they can conceive. (A) What are STDs? Besides sexual contact, what other means are responsible for transmission of sexually transmitted diseases? (B) The Government of India has prohibited prenatal sex determination by law. Explain the reason. (C) Name two bacterial and two viral infections caused due to unsafe sex.
Answer:
(A) STDs are infectious diseases caused by bacteria, viruses and other pathogens that spread through sexual contact. They can also spread by transfusion of blood from an infected person and by sharing injection needles.
(B) Prenatal sex determination is misused for illegal sex-selective abortion of female foetuses. Because of this the child sex ratio is declining, so the law prohibits it to stop female foeticide and to maintain the female-male sex ratio.
(C) Bacterial: gonorrhoea and syphilis. Viral: warts and AIDS.
In simple words: STDs spread by sexual contact, infected blood and needles; the law protects the girl child.

Teacher's Note:
1. Give two other means of transmission in part (A).
2. Name two examples each in part (C).

Question 9. Seema is a six years old child and noticed that all of a sudden, her brother who is 14 years old has grown very tall, his voice has started cracking and started having very fine hair on his face. She asked her mother whether she will also experience such changes when she grew up. Why and how these changes take place?
Answer:
1. These changes happen at puberty, when the reproductive organs begin to mature.
2. In boys the testes release the hormone testosterone, which brings the changes such as growth of facial hair, cracking of voice and increase in height.
3. Seema will also have changes, between about 10 and 12 years of age. The ovaries release the hormone oestrogen, which brings changes such as breast development, widening of hips and the start of menstruation.
In simple words: Hormones from the testes (boys) and ovaries (girls) cause these changes at puberty.

Teacher's Note:
1. Name the hormone for boys and for girls.
2. Reassure that the changes are natural.

Question 10. Meenakshi bought some strawberries and liked the taste. She is now curious to know: (A) Which method of cultivation is used to grow them? Define the method. (B) What are the advantages and disadvantages of the method adopted to grow strawberries?
Answer:
(A) Strawberry plants are commonly grown by vegetative propagation (from runners or stems). It is the method in which new plants are grown from a vegetative part of a plant such as the stem, root or leaf, without seeds.
(B) Advantages: it is cheaper, easier and faster than growing from seeds; the plants flower and fruit earlier; the desirable qualities of the parent are preserved.
Disadvantages: there is no genetic variation, so the plants are all open to the same disease, and no new varieties are produced.
In simple words: Strawberries are grown from parts of the plant, which is quick but gives no variation.

Teacher's Note:
1. Define the method in one line.
2. Give at least two points each for advantages and disadvantages.

Teacher's Note:
1. Read the 2013-15 column for (i) and (iv), and compare both columns for (v).
2. Female foeticide is a social problem as well as an illegal act.

Teacher's Note:
1. Subtract the two columns to find improvement or decline.
2. Learn that oral pills work by changing hormonal balance.

Question 13. The human males use a device X made of a very thin rubber sheet as a covering on the male organ to prevent pregnancy. This device traps the gametes Y in it. In order to prevent pregnancy, the human females use a device Z which is a circle of rubber with a metal spring around it. The device Z is put inside the vagina to cover the cervix. It stops Y from going into the uterus. (a) What is device X? (b) What are Y? (c) Name the device Z. (d) What is the general name of these methods of birth control (or preventing pregnancy)? (e) The use of which contraceptive device, X or Z, can protect the persons from sexually transmitted diseases?
Answer:
(a) X is a condom.
(b) Y are the sperms (male gametes).
(c) Z is a diaphragm.
(d) These are barrier methods (mechanical barriers) of contraception.
(e) The condom (X) can protect from sexually transmitted diseases, because it prevents the exchange of body fluids.
In simple words: A condom and a diaphragm are barriers that stop sperms from reaching the egg.

Teacher's Note:
1. Identify each device from the description.
2. Only the condom is known to protect against STDs here.

Question 14. There are four tiny organisms A, B, C and D. The organism A is a parasitic protozoan which causes a disease known as kala-azar. The organism B is a microscopic single-celled animal which causes malaria disease in human beings. The organism C is a unicellular animal which can change its body shape according to need, it has no fixed shape. The organism D is also a unicellular animal which is slipper-shaped having a large number of tiny hair all around its body. (a) Name the organisms A, B, C and D. (b) Name the one characteristic body feature of organism A. (c) Name the insect which carries organism B and transmits it from one person to another. (d) What name is given to the asexual method of reproduction of (i) organism A, and (ii) organism B? (e) Where do organisms C and D live?
Answer:
(a) A is Leishmania, B is Plasmodium, C is Amoeba and D is Paramecium.
(b) Leishmania has a whip-like structure (flagellum) at one end of its cell.
(c) The female Anopheles mosquito carries Plasmodium.
(d) (i) Leishmania reproduces by binary fission (in a definite orientation to the flagellum). (ii) Plasmodium reproduces by multiple fission.
(e) Amoeba and Paramecium live in fresh water such as ponds and ditches.
In simple words: These four are single-celled organisms that multiply by fission.

Teacher's Note:
1. Use the clues in the description to name each organism.
2. Remember: Leishmania = binary fission, Plasmodium = multiple fission.

Question 15. X and Y are two human beings. The organ A in the reproductive system of X releases a mature gamete B once a month which goes into a tube-like structure C through a funnel-like opening. The organ D in the reproductive system of Y makes and releases gametes E which pass through a duct F and are introduced by an organ of Y, into the body of X. B and E fuse together in C to form a new cell G. The cell G divides repeatedly to form a ball of cells H which gets embedded in the lining of organ I of reproductive system of X where it grows and develops into a baby. (a) Name (i) organ A, and (ii) gamete B. (b) Write two names of tube-like structure C. (c) Name (i) organ D, and (ii) gamete E. (d) Write two names of duct F. (e) Name (i) cell G (ii) ball of cells H, and (iii) organ I.
Answer:
(a) (i) Ovary (ii) egg (ovum).
(b) Oviduct, also called Fallopian tube (uterine tube).
(c) (i) Testis (ii) sperm.
(d) Vas deferens, also called sperm duct.
(e) (i) Zygote (ii) embryo (iii) uterus. The organ of Y that introduces the sperms into the body of X is the penis.
In simple words: The ovary releases an egg, the testis makes sperms, and they fuse in the oviduct to form a zygote.

Teacher's Note:
1. Trace the path: ovary, oviduct, zygote, embryo, uterus.
2. Use both names of the tube and the duct as asked.

Question 16. Mohan was watching his mother cutting some potatoes into small pieces, each with one or two buds. These buds have started sprouting. She planted them in kitchen garden and started watering them daily. Mohan asked his mother why she planted them as they have no seeds. (i) What is this method of propagation called? (ii) Which part of plant is used in this case? (iii) Is it sexual or asexual mode of reproduction?
Answer:
(i) It is called vegetative propagation.
(ii) The stem tuber (potato) is used, as the buds (eyes) on it sprout into new plants.
(iii) It is an asexual mode of reproduction, as no gametes are involved and only a single parent takes part.
In simple words: New potato plants grow from the buds of the potato piece, so no seeds are needed.

Teacher's Note:
1. Name the part: a potato is a modified stem.
2. Asexual = single parent, no gametes.

Question 17. The term Sexually Transmitted Disease (STD) refers to a condition passed from one person to another through sexual contact. However, it is not the only way STDs can be transmitted. An STD develops without any symptoms early on, or if any symptoms appear they are often dismissed as regular infections. At present, there are several types of STDs known which are caused by different types of pathogens. Some of these STDs are curable, while others are not. The only fool proof way of avoiding an STD is to practice safe sex. (i) Give two examples of STDs. (ii) Do you think like viruses, bacteria can also cause an STD? Give an example. (iii) Name a method of contraception which protects us from acquiring sexually transmitted diseases. (iv) What are IUCD? Give one example. (v) Emergency contraceptives may prevent pregnancy if used within 72 hrs of ... .
Answer:
(i) AIDS and genital warts (or gonorrhoea and syphilis).
(ii) Yes. For example, syphilis is an STD caused by the bacterium Treponema pallidum (and gonorrhoea by Neisseria gonorrhoeae).
(iii) The condom (a barrier method).
(iv) IUCD stands for Intra-Uterine Contraceptive Device. It is placed in the uterus to prevent pregnancy, for example Copper-T.
(v) Within 72 hours of unprotected sexual intercourse (coitus).
In simple words: STDs can be avoided by safe sex, and a condom also protects against them.

Teacher's Note:
1. Know examples from both viruses and bacteria.
2. Copper-T prevents pregnancy but does not stop STDs.

Question 18. Do you think sex-education is necessary in schools?
Answer:
1. Yes. Correct knowledge about the reproductive organs, the changes of adolescence, sexually transmitted diseases and contraception saves young minds from myths and misconceptions about sex-related matters.
2. It helps young people take responsible decisions, stay safe from infections and lead a reproductively healthy life.
In simple words: Right information at the right age keeps young people healthy and safe.

Teacher's Note:
1. Give your opinion first, then two reasons.
2. Use the terms reproductive health and STDs.

Question 19. How population growth can be prevented?
Answer:
1. By family planning programmes that spread awareness about the advantages of a small family.
2. By using birth control (contraceptive) methods: mechanical (barrier), chemical, surgical and natural methods.
3. By educating people and improving the standard of living, so that families choose to have fewer children.
In simple words: Family planning and contraception keep the population in check.

Teacher's Note:
1. Name the four types of birth control methods.
2. Mention awareness and education too.

Question 20. Write two causes of human population explosion. Explain with the help of a suitable examples how this explosion can be checked.
Answer:
Causes (any two): (i) reduced death rate due to better medical facilities; (ii) the desire for a male child, which leads to more children in a family; (iii) less awareness of birth control methods; (iv) illiteracy and poverty.
How to check it: (i) by using contraceptive methods, for example condoms, oral pills and Copper-T, or by surgical methods such as vasectomy and tubectomy; (ii) by creating awareness about the advantages of a small family.
In simple words: More births than deaths cause a population explosion; contraception and awareness check it.

Teacher's Note:
1. Write two causes and two measures.
2. Give examples of contraceptive methods.

Question 21. Write a short note on family planning.
Answer:
1. Family planning means regulating conception by contraceptive methods or devices to limit the number of children and to space them.
2. The methods are barrier methods (condom, diaphragm), intra-uterine devices (Copper-T), oral (hormonal) pills, and surgical methods (vasectomy in males and tubectomy in females).
3. It helps to control the population, protects the mother's health, avoids unwanted pregnancies and, with barrier methods, protects from STDs.
In simple words: Family planning helps couples decide the number of children and the gap between them.

Teacher's Note:
1. Mention the four types of methods.
2. State two benefits.