CBSE Class 10 Science How do humans reproduce Sure Shot Questions Set 04

This Class 10 Science page lists 20 sure shot questions on human reproduction from the chapter How Do Organisms Reproduce, each with a step-by-step answer, a simple-words summary and a teacher's note. The questions are the board-style ones asked most often: the placenta, the male and female reproductive systems, menstruation, puberty, contraception, STDs and AIDS, and reproductive health.

Sure Shot Questions on Human Reproduction

Question 1. What is placenta? Describe its structure. State its functions in case of a pregnant human female.
Answer:
1. The placenta is a special disc-like tissue embedded in the uterine wall. It connects the embryo to the mother and helps the embryo get nutrition from the mother's blood.
2. Structure: it has finger-like projections called villi on the embryo's side. On the mother's side there are blood spaces that surround the villi.
3. Functions: (i) it provides a large surface area for glucose, oxygen and other nutrients to pass from the mother's blood to the embryo; (ii) it removes the waste (carbon dioxide and nitrogenous wastes) made by the embryo by passing it into the mother's blood.
In simple words: The placenta feeds the baby and carries away its waste.

Teacher's Note:
1. Write structure and functions under separate headings.
2. Mention villi and blood spaces.

Question 2. Why are testes located outside the abdominal cavity? Mention the endocrine and exocrine functions of the testes.
Answer:
1. Sperm formation needs a temperature about 2 °C lower than the normal body temperature, and the scrotal sac outside the abdominal cavity provides it.
2. Endocrine function: the testes produce the hormone testosterone and release it into the blood.
3. Exocrine function: the testes produce sperms, which are carried out through the ducts.
In simple words: The testes stay outside to keep cool; they make testosterone and sperms.

Teacher's Note:
1. Give the reason for the location first.
2. Match endocrine with hormone and exocrine with sperms.

Question 3. (a) Write the function of the following in human female reproductive system: Ovary, oviduct, uterus. (b) How does the embryo get nourishment inside the mother's body? Explain in brief.
Answer:
(a) Ovary: produces the egg (female gamete) and secretes the female hormones oestrogen and progesterone. Oviduct (fallopian tube): carries the egg from the ovary to the uterus and is the site of fertilisation. Uterus: the embryo gets implanted here, and it holds and nourishes the growing foetus until the baby is ready for birth.
(b) The embryo gets nutrition from the mother's blood through the placenta, a disc-like tissue embedded in the uterine wall. Villi on the embryo's side and blood spaces on the mother's side give a large surface area for glucose and oxygen to pass to the embryo, and the embryo's waste passes to the mother's blood.
In simple words: The ovary makes eggs, the oviduct carries them, and the uterus grows the baby with the help of the placenta.

Teacher's Note:
1. Give one function for each organ in part (a).
2. Name the placenta in part (b).

Question 4. (a) Name the organ that produces sperms as well as secretes a hormone in human males. Name the hormone it secretes and write its functions. (b) Name the part of the human female reproductive system where fertilisation occurs. (c) Explain how the developing embryo gets nourishment inside the mother's body.
Answer:
(a) The testis produces sperms and secretes the hormone testosterone. Its functions: it stimulates sperm production, and it brings about the secondary sexual characters in boys at puberty, such as growth of beard and moustache and a deeper voice.
(b) Fertilisation occurs in the oviduct (fallopian tube).
(c) The embryo gets nourishment from the mother's blood through the placenta. Its villi dip into the mother's blood spaces, giving a large surface area for glucose and oxygen to pass to the embryo, and for wastes to pass back to the mother.
In simple words: The testis makes sperms and testosterone; the placenta feeds the embryo.

Teacher's Note:
1. Answer the three parts under (a), (b), (c).
2. Testosterone has two functions to write.

Question 5. State the changes that take place in the uterus when: (a) Implantation of embryo has occurred. (b) Female gamete/egg is not fertilised.
Answer:
(a) When the embryo is implanted, the inner lining of the uterus becomes thick and is richly supplied with blood vessels, so that it can nourish the growing embryo. (Later the placenta forms.)
(b) If the egg is not fertilised, it lives for about one day. The thickened lining is no longer needed, so it breaks down slowly and comes out through the vagina as blood and mucus. This is menstruation, which lasts about two to eight days.
In simple words: With an embryo the lining stays; without one the lining is shed.

Teacher's Note:
1. Name the process in (b): menstruation.
2. Write the duration of 2 to 8 days.

Question 6. Suggest three contraceptive methods to control the size of human population which is essential for the health and prosperity of a country. State the basic principle involved in each.
Answer:
1. Barrier method (condom, diaphragm): a physical barrier stops the sperms from meeting the egg. A condom also protects from STDs.
2. Chemical (hormonal) method (oral pills): the pills change the hormonal balance of the body so that eggs are not released and fertilisation cannot occur.
3. Surgical method: in vasectomy the vas deferens in males is cut and tied, and in tubectomy the oviducts in females are cut and tied, so sperms or egg cannot be carried and fertilisation does not occur.
(Copper-T, an intra-uterine device placed in the uterus by a doctor, prevents implantation.)
In simple words: Block the sperm, stop the egg or cut the passage: barrier, pills and surgery.

Teacher's Note:
1. Write the principle with each method.
2. Copper-T is placed by a doctor; it is not a surgical method.

Question 7. List any four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of a family?
Answer:
1. Four methods: condoms (barrier method); oral pills (chemical method); intra-uterine devices such as Copper-T; surgical methods (vasectomy in males and tubectomy in females).
2. Effect on health: they avoid unwanted pregnancies and frequent pregnancies, which protect the mother's physical and mental health, and they give a gap between two children.
3. Effect on prosperity: a small family can be given better food, clothing, health care and education, which makes the family happy and prosperous.
In simple words: Contraception spaces and limits births, so the mother stays healthy and the family can afford better care.

Teacher's Note:
1. Name four methods with examples.
2. Link family size to health and finance.

Question 8. Explain the meaning of sexually transmitted diseases (STDs). Give two examples of STDs each, caused due to (i) bacterial infection and (ii) viral infection. State in brief how the spread of such diseases may be prevented.
Answer:
1. STDs are diseases that spread from an infected person to a healthy person through sexual contact.
2. Examples: (i) bacterial infections: gonorrhoea and syphilis; (ii) viral infections: genital warts and HIV-AIDS.
3. Prevention: use of a condom during sexual contact, avoiding sexual contact with an infected person, and avoiding the sharing of injection needles.
In simple words: STDs spread by sexual contact and a condom is the best protection.

Teacher's Note:
1. Give two bacterial and two viral examples.
2. Say that condoms give protection.

Question 9. What does HIV stands for? Is AIDS an infectious disease? List any four modes of spreading AIDS.
Answer:
1. HIV stands for Human Immunodeficiency Virus. It causes AIDS (Acquired Immuno Deficiency Syndrome).
2. Yes, AIDS is an infectious disease, because it is passed from an infected person to others.
3. Modes of spreading: (i) unprotected sexual contact with an infected partner; (ii) use of contaminated needles and syringes; (iii) transfusion of infected blood; (iv) from an infected mother to her child through the placenta.
In simple words: HIV is the virus behind AIDS, and it spreads through blood and sexual contact.

Teacher's Note:
1. Expand HIV and AIDS correctly.
2. Write four modes of spread.

Question 10. List four points of significance of reproductive health in a society. Name any two areas related to reproductive health which have improved over the past 50 years in our country.
Answer:
1. Significance: (i) it prevents sexually transmitted diseases (STDs); (ii) it promotes the advantages of a small family; (iii) there is less mortality among new-born babies; (iv) there is less maternal mortality.
2. Areas that have improved: family planning and a decrease in the cases of STDs.
In simple words: Good reproductive health means safer mothers and babies and fewer infections.

Teacher's Note:
1. Write four short points.
2. Name two improved areas.

Question 11. (a) List three different categories of contraception methods. (b) Why has Government of India prohibited prenatal sex determination by law? State its benefits in the long run. (c) Unsafe sexual act can lead to various infections. Name two bacterial and two viral infections caused due to unsafe sex.
Answer:
(a) (i) Barrier methods (condom, diaphragm, and the Copper-T device); (ii) chemical (hormonal) methods such as oral pills; (iii) surgical methods (vasectomy and tubectomy).
(b) Prenatal sex determination was being misused for female foeticide, which makes the female-male sex ratio unbalanced. The ban stops this. In the long run it helps to maintain a healthy sex ratio and saves mothers from illegal abortions and the health problems they cause.
(c) Bacterial: gonorrhoea and syphilis. Viral: warts and HIV-AIDS.
In simple words: Three types of contraception; the law protects the girl child; STDs come from unsafe sex.

Teacher's Note:
1. Answer each part separately.
2. Name two examples in each category in (c).

Question 12. (a) Explain the terms: (i) implantation, (ii) placenta. (b) What is the average duration of human pregnancy?
Answer:
(a)(i) Implantation is the embedding of the embryo in the thick lining of the uterus.
(a)(ii) The placenta is a disc-like special tissue that develops between the uterine wall and the embryo. Through it the embryo receives nutrients and oxygen and gives out waste products.
(b) The average duration of human pregnancy is about nine months (about 40 weeks, or 280 days).
In simple words: Implantation fixes the embryo in the uterus; the placenta feeds it for about nine months.

Teacher's Note:
1. Define both terms in one line.
2. Remember 40 weeks.

Question 13. What are the changes seen in girls at the time of puberty?
Answer:
1. The pelvic region widens and fat is deposited on the hips, so the waist appears narrower.
2. The mammary glands (breasts) start developing, with dark nipples.
3. Hair appears in the pubic region and under the arms.
4. The menstrual cycle begins (menarche), and the size of the uterus and ovaries increases.
5. The skin becomes oilier, which may cause pimples.
In simple words: At puberty a girl's body changes shape and her monthly cycle begins.

Teacher's Note:
1. Write at least four changes.
2. The hormone responsible is oestrogen.

Question 14. List the parts of human male reproductive system which contribute to form semen. State two advantages semen offers to the sperms.
Answer:
1. The seminal vesicles and the prostate gland add their secretions to the sperms coming from the testes through the vas deferens, and together they form semen.
2. Advantages: (i) the fluid medium makes the transport of sperms easier; (ii) it provides nutrition (energy) to the sperms.
In simple words: Semen is a fluid that carries and feeds the sperms.

Teacher's Note:
1. Name two glands.
2. Write two advantages of semen.

Question 15. (a) What is the site of implantation and development of young one in human female? (b) Mention two advantages of using mechanical barriers during sexual act.
Answer:
(a) The uterus.
(b) (i) They prevent sexually transmitted diseases (STDs). (ii) They prevent the entry of sperms into the female genital tract, so they prevent unwanted pregnancy.
In simple words: The baby develops in the uterus, and barriers protect against STDs and pregnancy.

Teacher's Note:
1. Condom is the standard example of a mechanical barrier.
2. Write two separate advantages.

Question 16. (a) How many eggs are produced every month by either of the ovaries in a human female? Where does fertilization take place in the female reproductive system? (b) What happens in case the eggs released by the ovary are not fertilized?
Answer:
(a) One egg is produced every month by one of the ovaries. Fertilisation takes place in the fallopian tube (oviduct).
(b) The unfertilised egg lives for about a day. The thick lining of the uterus then breaks down and comes out through the vagina with blood and mucus as menstruation.
In simple words: One egg a month; unfertilised eggs leave with the uterine lining as menstruation.

Teacher's Note:
1. Note: one egg per month, from one ovary.
2. Name the process in (b).

Question 17. Name the sex hormones secreted by male and female sex organs in human beings. State one function of each.
Answer:
1. Male (testes): testosterone. It controls the production of sperms and brings about the changes of puberty in boys.
2. Female (ovaries): oestrogen (and progesterone). Oestrogen brings about the changes of puberty in girls, such as breast development, and helps build up the lining of the uterus.
In simple words: Testosterone works in boys and oestrogen in girls.

Teacher's Note:
1. Name one hormone for each sex.
2. Give one function each.

Question 18. (a) State any two changes seen in boys at the time of puberty. (b) Define fertilization and implantation. (c) State the role of ovary and fallopian tube in human body.
Answer:
(a) (i) Thick hair growth on the face. (ii) The voice begins to crack (deepens).
(b) Fertilisation is the fusion of the haploid male and female gametes to form a diploid zygote. Implantation is the attachment of the embryo to the wall of the uterus for further development.
(c) The ovary produces the female gamete (egg) and the hormones oestrogen and progesterone. The fallopian tube carries the egg to the uterus and is the site where fertilisation occurs.
In simple words: Boys grow facial hair and a deeper voice; the ovary makes eggs and the tube is the meeting place.

Teacher's Note:
1. Answer (a), (b) and (c) separately.
2. Define fertilisation and implantation precisely.

Question 19. (a) "Use of a condom is beneficial for both the sexes involved in a sexual act." Justify this statement giving two reasons. (b) How do oral contraceptive help in avoiding pregnancies? (c) What is sex selective abortion? How does it affect a healthy society? (State any one consequence)
Answer:
(a) (i) It prevents unwanted pregnancy, which could harm the woman's health and the couple's life. (ii) It protects both partners from sexually transmitted diseases such as AIDS.
(b) Oral contraceptives are hormonal pills. They change the hormonal balance of the body so that eggs are not released from the ovary, and fertilisation cannot take place.
(c) Sex selective abortion is the removal of a foetus by surgical abortion because its sex is not the one wanted (usually a female foetus). It lowers the number of girls, so the child sex ratio declines and the society becomes unbalanced.
In simple words: Condoms protect both partners, pills stop the egg from being released, and sex-selective abortion harms society.

Teacher's Note:
1. Give two reasons in part (a).
2. Name one consequence in part (c).

Question 20. What could be the reasons for adopting contraceptive method?
Answer:
1. To prevent unwanted pregnancies and to control population growth.
2. To protect from sexually transmitted diseases such as AIDS and syphilis (barrier methods).
3. To maintain the proper health of the mother and child by avoiding frequent pregnancies.
4. To keep a sufficient gap between children.
In simple words: Contraceptives help to plan a family and keep people safe from infection.

Teacher's Note:
1. Write at least three reasons.
2. Link them to health and population.