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NCERT Exemplar Solutions for Class 12 Biology chapter 4 Reproductive Health

These Solutions are part of NCERT Exemplar Solutions for Class 12 Biology. Here we have given NCERT Exemplar Solutions for Class 12 Biology chapter 4 Reproductive Health

Multiple Choice Questions

Question 1.
The method of directly injecting a sperm into ovum in assisted reproductive technology is called
(a) GIFT
(b) ZIFT
(c) ICSI   
(d) ET.
Answer:
(c) : ICSI or Intra Cytoplasmic Sperm Injection is one of the techniques of Assisted Reproductive Technology (ART) that helps couples to overcome their infertility. In ICSI, sperm is directly injected into ovum, in vitro to form zygote, which is implanted through ZIFT into woman.

Question 2.
Increased IMR and decreased MMR in a population will
(a) cause rapid increase in growth rate
(b) result in decline in growth rate
(c) not cause significant change in growth rate
(d) result in an explosive population/exp.
Answer:
(b) : If there is an increase in infant mortality rate (IMR) and decrease in maternal mortality rate (MMR), mothers are available to give birth to infants but the infants’ survival rate is low, which will ultimately hinder the growth rate of that particular population.

Question 3.
Intensely lactating mothers do not generally conceive due to the
(a) suppression of gonadotropins
(b) hypersecretion of gonadotropins
(c) suppression of gametic transport
(d) suppression of fertilisation.
Answer:
(a) : Presence of prolactin hormone in the blood of lactating mothers suppresses the release of gonadotropins (FSH and LH) from the pituitary gland. Gonadotropins are required for ovulation to occur. Thus, in the absence of, gonadotropins, ovum is not released and hence chances of fertilisation are nil upto 6 months following parturition (if the mother is regularly breast-feeding). Therefore, intensely lactating mothers do not generally conceive.

Question 4.
Sterilisation techniques are generally fool proof methods of contraception with least side effects. Yet, this is the last option for the couples because
(1) it is almost irreversible
(2) of the misconception that it will reduce sexual urge/drive
(3) it is a surgical procedure
(4) of lack of sufficient facilities in many parts of the country
Choose the correct option.
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (ii) and (iv)
(d) (i), (ii), (iii) and (iv)
Answer:
(d) : Sterilisation techniques are surgical procedures where, in males, vas deferens are cut and tied and in females, Fallopian tubes are cut and tied, preventing gamete transport.
Even though it is very effective it is often used as a last option by most couples. One, because it is almost irreversible. Second, because of some misconceptions like absence of ejaculation and lowering of sexual urge.Third, because it is a surgical procedure, there are certain risk of infection. Last but not least,
there are lack of sufficient facilities in many parts of our country (e.g., lack of hygiene, lack of qualified personnel etc.)

Question 5.
A national level approach to build up a reproductively healthy society was taken up in our country in
(a) 1950s
(b) 1960s
(c) 1980s
(d) 1990s
Answer:
(a) : The national level approach towards building a reproductively healthy society began with ‘family planning’ programmes in 1951. Over last 6 decades many other programmes have been started. In 2000, National Population Policy was launched and in 2005, National Rural Health Mission (NRHM) was launched, with the aim of revamping the public health services in rural areas. Janani Suraksha Yojana has also been launched which includes conditional cash transfer. Other improved programmes are also initiated with the term of ‘Reproductive and child Health Care’ (RCH). Launching a number of schemes will benefit only when people are aware of them and those working at the various stages of implementation are doing their work honestly and with right intention.

Question 6.
Emergency contraceptives are effective if used within
(a) 72 hrs of coitus
(b) 72 hrs of ovulation
(c) 72 hrs of menstruation
(d) 72 hrs of implantation.
Answer:
(a)

Question 7.
Choose the right one among the statements given below.
(a) lUDs are generally inserted by the user herself.
(b) lUDs increase phagocytosis reaction in the uterus.
(c) lUDs suppress gametogenesis.
(d) lUDs once inserted need not be replaced.
Answer:
(b) : Copper releasing IUDs (CuT, multiload) increase phagocytosis of sperms within the uterus and the Cu ions released suppress sperm motility and the fertilising capacity of sperms. The hormone releasing IUDs (progestaserf, LNG-20), make the uterus unsuitable for implantation and the cervix hostile to the sperms. IUDs are inserted and removed by trained doctors and they are ideal contraceptives for the females. IUDs, once inserted can be there for a long period of time (even years), especially, copper releasing IUDs. But eventually they need to be removed and replaced, as they are foreign to the body. Fertility returns, once IUDs are removed.

Question 8.
Following statements are given regarding MTP. Choose the correct options given below.
(1) MTPs are generally advised during first trimester.
(2) MTPs are used as a contraceptive method.
(3) MTPs are always surgical.
(4) MTPs require the assistance of qualified medical personnel.
(a) (ii) and (iii)
(b) (i) and (iii)
(c) (i) and (iv)   
(d) (i) and (ii)
Answer:
(c) : Voluntary termination of pregnancy before full term is called Medical Termination of Pregnancy (MTP). It is less riskier during first trimester (upto 12^th week) and requires assistance of qualified medical personnel. Surgical methods of termination of pregnancy include vacuum aspiration of the products of conception through an intra-uterine cannula, etc. It can also be induced using chemical drugs, e.g., mifepristone and prostaglandin. These drugs are taken only in the supervision of qualified medical personnel.

Question 9.
From the sexually transmitted diseases  mentioned below, identify the one which does not specifically affect the sex organs.
(a) Syphilis
(b) AIDS
(c) Gonorrhoea
(d) Genital warts
Answer:
(b) : AIDS (Acquired Immune Deficiency Syndrome) is caused by HIV (Human Immunodeficiency Virus, a retrovirus). It mainly affects the T-helper lymphocytes by infecting them. There is generally a long time lag between infection and occurrence of symptoms. Because of lowering of T-helper lymphocyte count, the person becomes vulnerable to infectious microorganisms, that otherwise, wouldn’t have caused any disease(opportunistic infection). A major example of this is tuberculosis. Weight loss also occurs in such persons.

Question 10.
Condoms are one of the most popular contraceptives because of the following reasons.
(a) These are effective barriers for insemination.
(b) They do not interfere with coital act.
(c) These help in reducing the risk of STDs.
(d) All of the above.
Answer:
(d)

Question 11.
Choose the correct statement regarding the ZIFT procedure.
(a) Ova collected from a female donor are transferred to the Fallopian tube to facilitate zygote formation.
(b) Zygote is collected from a female donor and transferred to the Fallopian tube.
(c) Zygote is collected from a female donor and transferred to the uterus.
(d) Ova collected from a female donor and transferred to the uterus.
Answer:
(None) : In test tube baby programme, ovum from donor female/wife and sperm from donor male/husband are induced to form zygote in the laboratory. The zygote is allowed to divide upto 8 blastomeres in the laboratory. Zygote or early embryo is then transferred into the Fallopian tube. This technique is called ZIFT (Zygote Intra Fallopian Transfer).

Question 12.
The correct surgical procedure as a contracep­tive method is
(a) ovariectomy
(b) hysterectomy
(c) vasectomy
(d) Casttation
Answer:
(c) : Vasectomy is a surgical contracep­tion method performed in males. In vasectomy a small part of the vas deferens is removed or tied up through a small cut on the scrotum.

Question 13.
Diaphragms are contraceptive devices used by the females. Choose the correct option from the statements given below.
(1) They are introduced into the uterus.
(2) They are placed to cover the cervical region.
(3) They act as physical barriers for sperm entry.
(4) They act as spermicidal agents.
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (iii) and (iv)
Answer:
(c) : Diaphragms are soft, hemispherical rubber cups fitted inside the vagina over the neck (cervix) of the uterus acting as physical barrier for sperm entry. When combined with the use of a chemical spermicide, they provide reliable contraception.

Very Short Answer Type Questions

Question 1.
Reproductive health refers only to healthy reproductive functions. Comment.
Answer:
According to WHO (World” Health Organisation), reproductive health means total well being of a person in all aspects of reproduction, i.e. physical, emotional, behavioral and social. It does not only refer to healthy reproductive functions.

Question 2.
Comment on the Reproductive and Child Health Care programme of the government to improve the reproductive health of the people
Answer:
RCH (Reproductive and Child Health Care) Programme aims at improving reproductive health of the society. Various measures undertaken by this programme include creating awareness among people about various reproduction related aspects, providing facilities and support for building up a reproductively healthy society, educating fertile couples about birth control measures, prenatal and postnatal care of mother and child, etc.

Question 3.
The present population growth rate in India is alarming. Suggest ways to check it.
Answer:
Ways to check present population growth rate are:
(1) Educating people by various audiovisual means about the advantages of small families.
(2) Making them aware of ill effects of overpopulation.
(3) Implementing family planning pro­grammes sincerely to achieve zero population growth.
(4) Increasing marriageable age limit.

Question 4.
STDscan be considered as self-invited diseases. Comment.
Answer:
Sexually Transmitted Diseases (STDs) can be considered as self-invited diseases because one could be free of these by following simple precautions. These are as follows:

• Avoid sex with unknown partners/multiple partners.
• Always use condoms during coitus.
• In case of doubt, one should go to a doctor for early detection and complete treatment.

Question 5.
Suggest the reproduction related aspects in which counselling should be provided at the school level.
Answer:
Introduction of sex education in schools is another step to give right information to the young minds about reproductive organs, accessory organs of reproduction, secondary sexual characters, adolescence and related changes, safe and hygienic sexual practices, sexually transmitted diseases, birth control methods etc. This knowledge will save them from myths and misconceptions about sex related aspects.

Question 6.
Mention the primary aim of the “Assisted Reproductive Technology” (ART) programme.
Answer:
ART (Assisted Reproductive Technology) programme assists the infertile couples to have children through some special techniques. It includes various programmes like test tube babies, ZIFT, GIFT, AIT, ICSI etc.

Question 7.
What is the significance of progesterone- estrogen combination as a contraceptive measure?
Answer:
Birth control pills like Mala D and Mala N have progesterone-estrogen combinations, and are commonly called combination pills. They inhibit ovulation and implantation.

Question 8.
Strict conditions are to be followed in medical termination of pregnancy (MTP) procedures. Mention two reasons.
Answer:
Two reasons for following strict condi­tions in medical termination of pregnancy (MTPs) are:

1. It is being misused to abort even the normal female foetuses.
2. MTP performed after first trimester i.e., 12 weeks of pregnancy becomes riskier as foetus becomes more deeply associated with uterine tissue of mother.

Question 9.
Males in whom testes fail to descend to the scrotum are generally infertile. Why?
Answer:
Sperms need slightly lower temperature than body temperature to survive, which is provided by scrotal sac. If testes fail to descend into scrotum, sperms will get killed at high temperature present in abdomen and the person will become infertile.

Question 10.
Mention two advantages of lactational amenorrhea as a contraceptive method.
Answer:
Two advantages of lactational amenorrhea as a contraceptive method are as follows:

1. During intense lactation after parturition, mother does not undergo menstruation and ovulation as high levels of prolactin suppresses ‘ secretion of gonadotropins from anterior pituitary.
2. No medicines or devices are used in this method thus, side effects are almost nil.

Short Answer Type Questions

Question 1.
Suggest some important steps that you would recommend to be taken to improve the reproductive health standards in India.
Answer:
Following measures are needed to be undertaken to improve the reproductive health standards in India :

1. Implementation of RCH (Reproductive and .Child Health Care) and family  planning programmes.
2. To follow child immunisation programme.
3. Introduction of sex education in schools to remove myths and misconceptions about sex related issues.
4. To impose statutory ban on amniocentesis and to check female foeticide.
5. To educate people about various health related programmes and family planning programmes.
6. To control sexually transmitted diseases.
7. Create fertility clinics to diagnose and treat disorders related to infertility.

Question 2.
The procedure of GIFT involves the transfer of female gamete to the Fallopian tube. Can gametes be transferred to the uterus to achieve the same result? Explain.
Answer:
The results will not be the same if gametes are introduced into the uterus, instead of Fallopian tube in the procedure of GIFT. This can be explained as follows. The Fallopian tube and its micro environment are ideal for fertilisation and early embryo development. The anatomy and physiology of Fallopian tube plays an important role in egg transport and fertilisation. Zygote formed as a result of fertilisation, divides to form embryo. Complex interactions take place between oviducal epithelium and the embryo. Human oviducal cells are known to secrete growth factors, cytokines and embryotrophic factors (ETFs) that enhance and support the development of the pre­implantation embryos. On the other hand, the uterine environment is not appropriate for the survival of the gametes, they may undergo degeneration or get phagocytosed in uterus and zygote formation will not be achieved.

Question 3.
Copper ions-releasing lUDs are more efficient than non-medicated methods. Why?
Answer:
Copper releasing IUDs like Cu-T, Cu-7, multi load 375 etc., are more efficient than non- medicated methods because non-medicated methods simply act as barriers for sperm entry into the reproductive tract of female and are not fool proof whereas copper ion releasing IUDs release Cu ions which suppress the sperm motility and fertilising capacity of the sperms and act as better contraceptives.

Question 4.
What are the probable factors that contributed to population explosion in India?
Answer:
Factors favouring population explosion are :

1. Lack of education in developing countries.
2. Lack of entertainment and gainful employ­ment in under-developed countries.
3. Early marriage, child labour.
4. Desire of male child, traditional religious beliefs etc.

Question 5..
Briefly explain IVE and ET. What are the conditions in which these methods are advised?
Answer:
In 1VF (In Vitro Fertilisation), fertilisation takes place outside the body of female in similar conditions as that in the body followed by E.T (Embryo Transfer). It is performed as follows:

1. Ova from the wife/donor female and sperms from husband/donor male are collected in hygienic manner.
2. Both ova and sperms are kept in culture medium under aseptic conditions.
3. Gametes are induced to fuse, and form zygote under simulated conditions.

In ET (Embryo Transfer) technique, developing embryo is transferred from culture medium to female reproductive tract. It is performed as follows:

1. Zygote is induced in culture medium to develop.
2. Endometrium is stimulated to be prepared for implantation.
3. Embryo is transferred to Fallopian tubes in 8 celled condition or transferred to uterus when it is at 16-32 celled stage. When in a woman normal conception is not possible because of blocked oviducts or spermicidal secretions in the vagina or when a woman cannot produce ova or man cannot produce sperms. In such conditions these methods are advised.

Question 6.
What are the advantages of natural methods of contraception over artificial methods?
Answer:
Natural methods of contraception include rhythm method, coitus interruptus and lactational amenorrhea. These methods do not involve use of any contraceptive or any chemical or surgery therefore, do not have any side effects. On the other hand, artificial methods of contraception which include IUDs, oral pills etc., have certain drawbacks. IUDs may cause occasional haemorrhage or infections. Combined oral pills generally have side effects like nausea, breast tenderness, weight gain, breakthrough bleeding and melasma etc.

Question 7.
What are the conditions in which medical termination of pregnancy is advised?
Answer:
The conditions in which medical termination of pregnancy is advised are as follows :

1. To get rid of unwanted pregnancy either due to unprotected intercourse or failure of the contraceptive used or rape.
2. If baby is suffering from an incurable and congenital developmental defect.
3. If continuation of pregnancy is harmful or even fatal either to mother, or to foetus or both.

Question 8.
Comment on the essential features required for an ideal contraceptive.
Answer:
An ideal contraceptive should be:

1. User friendly
2. Easily available and cheaper
3. Effective but also reversible
4. With no or least side effects
5. Should not interfere with the sexual act.

Question 9.
All reproductive tract infections RTIs are STDs, but all STDs are not RTIs. Justify with example.
Answer:
STDs are sexually transmitted diseases and include gonorrhoea, syphilis, genital warts, chlamydiasis, hepatitis B and AIDS. Hepatitis B and AIDS are not RTFs because they do not cause any infection in the reproductive tract but are spread through sexual means, whereas other diseases are STDs as well as RTIs.

Long Answer Type Questions

Question 1.
What are the Assisted Reproductive Techniques practiced to help infertile couples? Describe any three techniques.
Answer:
Assisted reproductive techniques are employed to diagnose and treat the infertile couples to have children. A few techniques are described as follows:

(1) Test tube babies : In this technique the fusion of ovum and sperm is done outside the body of the female to form a zygote Which is allowed to divide to form an embryo. This embryo is- then implanted in the uterus, where it develops into a foetus.

(2) Gamete Intra Fallopian Transfer (GIFT) : This method is vised in females, who can not produce ova, hut can provide suitable environment for fertilisation and further development of embryo in the oviducts. In such cases, ovum from the donor female is introduced into the Fallopian tube of such female. Such women accept sperms from their husbands during copulation.

(3) Intra Cytoplasmic Sperm Injection (ICSI) : It is another specialised technique to form an embryo in laboratory in which a I  sperm is directly injected into the ovum placed in a nutrient broth. The zygote or early embryo is later transferred to the Fallopian tube of woman by ZIFT.

Question 2.
Discuss the mode of action and advantages/disadvantages of hormonal contraceptives.
Answer:
Various hormonal contraceptives are:

1. Hormone releasing IUDs
2. Oral pills
3. Implants
4. Hormone injections

(1) Hormone releasing IUDs – Hormone  releasing IUDs include progestasert and LNG-20. They turn the cervix hostile to spermatozoa and bring changes in  the uterus making it unsuitable for implantation.

(2) Oral pills – They contain progestin  (progesterone like synthetic hormone) alone or a combination of synthetic progesterone and oestrogen. They inhibit the secretion of FSH and LH from anterior pituitary and inhibit ovulation and implantation. They also retard the entry of sperms in the uterus by changing the quality of cervical mucus.

(3) Subcutaneous implants – In this contraception method, six matchstick sized capsules containing synthetic progesterone are inserted under the skin of inner arm above the elbow. It acts similarly to oral contraceptives by blocking ovulation and thickening the cervical mucus to prevent sperm transport.

(4) Hormone injections – These are pro­ gesterone injections which are given once every 3 months and release hormone slowly and prevent ovulation. follows :
Various contraceptive techniques play significant role in checking the uncontrolled growth of human population. They are required to prevent pregnancy.

Disadvantages of hormonal contraceptives are as follows :
These hormone releasing contraceptives especially have many side effects. Use of IUDs possesses the risk of perforation of uterus and infection. Oral contraceptives can cause nausea, weight gain, breast tenderness, breakthrough bleeding, high blood pressure and melasma.

Question 3.
STDs are a threat to reproductive health. Describe any two such diseases and suggest preventive measures.
Answer:
Sexually transmitted disease (STDs) are threat to reproductive health. They are infectious, communicable and acquired diseases. They may lead to various complications like PID (pelvic inflammatory diseases), abortions, still birth, ectopic pregnancies, infertility or even cancer of reproductive tract. Some sexually transmitted diseases are discussed as follows :
(1) AIDS — It is caused by Human Immuno­deficiency Virus (HIV)
Symptoms – Fever, lethargy, pharyngitis, weight loss, nausea, headache, rashes etc.
HIV attacks helper T-lymphocytes. The patient gets immune deficiency and he/ she is unable to protect himself/herself against infections.

(2) Hepatitis B – It is caused by Hepatitis B virus (HBV).
Symptoms – Fatigue, jaundice, persistent low grade fever, rash and abdominal pain. It can also cause cirrhosis and possibly liver cancer.
STDs can be prevented by following ways:

• Use of condoms during coitus.
• Avoiding sex with unknown partners/ multiple partners.
• In case of doubt, consulting a qualified doctor for early detection and getting complete- treatment if diagnosed with disease.

Question 4.
Do you justify the statutory ban on amniocentesis in our country? Give reasons.
Answer:
Amniocentesis (along with sonography) is being misused to determine the sex of the foetus. Due to small family norm, along with religion and social practices, every family wants a male child. The female foetus is destroyed. This has resulted in decline in female population to less than 50 per 100 males in certain areas. Such an imbalance in sex ratio is bound to create social problems for the future generations. Therefore, statutory ban on the test is a rational move.

Question 5.
Enumerate and describe any five reasons for introducing sex education to school-going children.
Answer:
Introduction of sex education is necessary in schools because of the following reasons:

1. ,It will provide correct information about sex related matters and reproductive organs and will help removing all misconceptions and myths.
2. It can explain changes during adolescence. Help can be provided if there is any abnormality.
3. It can predict the changes in behaviour and prevent development of mental problems.
4. It will explain the harms of early sex and early marriage.
5. It will provide proper knowledge of cleanliness of genitalia and other organs.
6. It will provide correct information about sexually transmitted diseases.
7. It will give information about methods of family planning and hygienic sexual practices.

We hope the NCERT Exemplar Solutions for Class 12 Biology chapter 4 Reproductive Health help you. If you have any query regarding .NCERT Exemplar Solutions for Class 12 Biology chapter 4 Reproductive Health, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Solutions for Class 12 Biology chapter 3 Human Reproduction

These Solutions are part of NCERT Exemplar Solutions for Class 12 Biology. Here we have given NCERT Exemplar Solutions for Class 12 Biology chapter 3 Human Reproduction

Multiple Choice Questions

Question 1.
Choose the incorrect statement from the following. 
(a) In birds and mammals internal fertilisation takes place.
(b) Colostrum contains antibodies and nutrients.
(c) Polyspermy in mammals is prevented by the chemical changes in the egg surface.
(d) In the human female implantation occurs almost seven days after fertilisation.
Answer:
(c) : Polyspermy is the entry of several sperms into the egg during fertilisation. It occurs in animals with yolky eggs (e.g., birds). In humans, although only one sperm nucleus actually fuses with the egg nucleus. Due to acrosomal reaction, plasma membrane of the sperm fuses with the plasma membrane of the secondary oocyte, so that the sperm contents enter the oocyte. Binding of the sperm to the secondary oocyte induces depolarisation of the oocyte plasma membrane. Depolarisation  prevents polyspermy.

Question 2.
Identify the correct statement from the following.
(a) High levels of estrogen triggers the ovulatory surge.
(b) Oogonial cells start to proliferate and give rise to functional ova in regular cycles from puberty onwards.
(c) Sperms released from seminiferous tubules are highly motile.
(d) Progesterone level is high during the post ovulatory phase of menstrual cycle.
Answer:
(d)

Question 3.
Spot the odd one out from the following structures with reference to the male reproductive system.
(a) Rete testis
(b) Epididymis
(c) Vasa efferentia
(d) Isthmus
Answer:
(d) : Females have two oviducts (or Fallopian tubes). Each oviduct has three regions, infundibulum, ampulla and isthmus. Isthmus is the narrow part closest to uterus, while infundibulum is the first part of oviduct that is encountered by released ova.

Question 4.
Seminal plasma, the fluid part of semen, is contributed by
(1) seminal vesicle
(2) prostate
(3) urethra
(4) bulbourethral gland
(a) (i) and (ii)
(b) (i), (ii) and (iv)
(c) (ii), (iii) and (iv)
(d) (i) and (iv)
Answer:
(b) : Seminal plasma is the fluid part of semen and is contributed by seminal vesicles, prostate gland and bulbourethral glands. Seminal vesicles contribute fructose, citric acid and other nutrients as well as fibrinogen and prostaglandins. Secretions from prostate gland contain calcium ions, phosphate ion etc. and are alkaline in nature. Bulbourethral glands secrete alkaline mucus which is important for the lubrication of penis.

Question 5.
Spermiation is the process of the release of sperms from
(a) seminiferous tubules
(b) vas deferens
(c) epididymis
(d) prostate gland.
Answer:
(a) : Spermiation is the release of sperm from seminiferous tubules. From here, they will be transported to vasa efferentia and then to epididymis where maturation of sperm occurs.

Question 6.
Mature Graafian follicle is generally present in the ovary of a healthy human female around
(a) 5-8 day of menstrual cycle
(b) 11-17 day of menstrual cycle
(c) 18-23 day of menstrual cycle
(d) 24-28 day of menstrual cycle.
Answer:
(b) : Starting from puberty, monthly changes in ovaries and uterus also starts. The layer of cells surrounding primary oocyte are called granulosa cells and together, they are  called primary follicle. The growth of the follicles is under the influence of pituitary hormones FSH and LH. Further growth is also stimulated by estrogen. The mature Graafian follicle is present in the ovary around 11-17 day of menstrual cycle and on rupture of which, ovum is released (because of LH surge, 1-2 days before ovulation).

Question 7.
Acrosomal reaction of the sperm occurs due to
(a) its contact with zona pellucida of the ova
(b) reactions within the uterine environment of the female
(c) reactions within the epididymal environ­ment of the male
(d) androgens produced in the uterus.
Answer:
(a) : When head of sperm binds to zona pellucida (ZP) of ovum the acrosome release its contents by exocytosis. The content inside acrosome includes various hydrolytic enzymes like hyaluronidase, corona penetrating enzymes etc. This is called acrosomal reaction. It helps the sperm to reach the plasma membrane of ovum, by dissolving corona radiata and zona pellucida.

Question 8.
Which one of the following is not a male accessory gland?
(a) Seminal vesicle
(b) Ampulla
(c) Prostate
(d) Bulbourethral gland
Answer:
(b) : Ampulla is the part of oviduct between the infundibulum and isthmus. It  is at tfre ampullary-isthmus junction, where fertilisation take place.

Question 9.
The immature male germ cell undergoes division to produce sperms by the process of spermatogenesis. Choose the correct one with reference to above.
(a) Spermatogonia have 46 chromosomes and always undergo meiotic cell division.
(b) Primary spermatocytes divide by mitotic cell division.
(c) Secondary spermatocytes have 23 chromo­somes and undergo second meiotic division.
(d) Spermatozoa are transformed into spermatids.
Answer:
(c) : Spermatogonia are diploid cells on the inside wall of seminiferous tubules that multiply by mitotic divisions. Some of the spermatogonia called primary spermatocyte undergo meiosis-I to give rise to secondary spermatocytes (haploid). Each secondary spermatocyte undergoes meiosis-II to give rise to two haploid spermatids which are transformed to spermatozoa by spermiogenesis.

Question 10.
Match between the following representing parts of the. sperm and their functions and choose the correct option.

(a) A-{ii), B-(iv), C-(i), D-(iii)
(b) A-(iv), B-(iii), C-(i), D-(ii)
(c) A-(iv), B-(i), C-(ii), D-(iii)
(d) A-(ii), B-(i), C-(iii), D-(iv)
Answer:
(b)

Question 11.
Which among the following has 23 chromo­somes?
(a) Spermatogonia
(b) Zygote
(c) Secondary oocyte .
(d) Oogonia
Answer:
(c) : Spermatogonia are the cells on the inside wall of seminiferous tubules and consist of 46 chromosomes. Oogonia are also diploid cells and formed in the foetal ovary. Zygote is also diploid and fertilised ovum formed by fusion of male and female gametes. Secondary oocyte has 23 chromosomes and is formed by meiosis-I of primary oocyte.

Question 12.
Match the following and choose the correct option.

(a) A-(ii), B-(i), C-(iii), D-(iv)
(b) A-(iii), B-(iv), C-(ii), D-(i)
(c) A-(iii), B-(i), C-(ii), D-(iv)
(d) A-(ii), B-(iv), C-(iii), D-(i)
Answer:
(b)

Question 13.
Which of the following hormones is not secreted by human placenta?
(a) hCG
(b) Estrogens
(c) Progesterone
(d) LH
Answer:
(d) : LH is the hormone that is not secreted by human placenta. It is secreted by anteribr pituitary. Initially during pregnancy, hCG performs the function of LH of maintaining corpus luteum for the secretion of progesterone. Later (around 16^th week) in pregnancy, when placenta itself starts secreting estrogen and progesterone, corpus luteum regresses.

Question 14.
The vas deferens receives duct from the seminal vesicle and opens into urethra as
(a) epididymis
(b) ejaculatory duct
(c) efferent ductule
(d) Ureter
Answer:
(b)

Question 15.
Urethral meatus refers to the
(a) urinogenital duct
(b) opening of vas deferens into urethra
(c) external opening of the urinogenital duct
(d) muscles surrounding the urinogenial duct.
Answer:
(c) : Urethral meatus refers to the external opening of urinogenital duct, through which in males, urine and semen both exits the body.

Question 16.
Morula is a developmental stage
(a) between the zygote and blastocyst
(b) between the blastocyst and gastrula
(c) after the implantation
(d)between implantation and parturition.
Answer:
(a) : After fertilisation, zygote is formed. Zygote undergoes, mitotic divisions, called cleavage, to form 2, 4, 8 and 16 daughter cells called blastomeres. These divisions start when zygote is moving towards uterus. It is called morula at 8-16 cell stage and it continues to divide to form blastocyst. Blastocyst has two type of cells : trophoblast cells and inner cell mass. Around 7 day after fertilisation, implantation through trophoblast cells occurs.

Question 17.
The membranous cover of the ovum at ovulation is
(a) corona radiata
(b) zona radiata
(c) zona pellucida
(d) Chorion
Answer:
(a) : The outermost membranous cover of the ovum at ovulation is corona radiata. It is formed by follicular cells. Inner to corona radiata is zona pel lucid a, which is made up of three different glycoproteins secreted by the ovum itself.

Question 18.
Identify the odd one from the following.
(a) Labia minora
(b) Fimbriae
(c) Infundibulum
(d) Isthmus
Answer:
(a) : Labia minora are paired folds of tissues under labia majora which in turn surrounds the vaginal opening. Fimbriae, infundibulum and isthmus, along with ampulla are parts of oviduct (or Fallopian tube).

Very Short Answer Type Questions

Question 1.
Given below are the events in human reproduction. Write them in correct sequential order. Insemination, gametogenesis, fertilisation, parturition, gestation, implantation
Answer:
Gametogenesis, insemination, fertilisa­tion, implantation, gestation, parturition.

Question 2.
The path of sperm transport is given below. Provide the missing steps in blank boxes.

Answer:
Seminiferous tubules —>Rete testis —> Vasa efferentia —> Epididymis —> Vas deferens -> Urethra

Question 3.
What is the role of cervix in the human female reproductive system?
Answer:
Role of cervix in human female reproductive system:

1. Cervical canal e., the cavity of cervix and vagina together form birth canal to facilitate parturition.
2. It regulates the passage of sperms into the uterus.

Question 4.
Why are menstrual cycles absent during pregnancy?
Answer:
Levels of progesterone and estrogen are high during pregnancy. Their high levels suppress the release of gonadotropin (FSH) responsible for transformation of primary follicles into Graafian follicles, and for ovulation. And, no ovulation means, no menstrual cycle.

Question 5.
Female reproductive organs and associated functions are given below in column A and B. Fill the blank boxes.

Answer:
a – Fertilisation, b – Uterus

Question 6.
From where the parturition signals arise- mother or foetus? Mention the main hormone involved in parturition.
Answer:
Parturition is induced by complex neuroendocrine mechanism. Signals for parturition originate from fully developed foetus and placenta which induce mild uterine contractions called foetal ejection reflex. Oxytocin from maternal pituitary induces strong uterine contractions of myometrium, which leads to expulsion of baby (parturition) through birth canal.

Question 7.
What is the significance of epididymis in male fertility?
Answer:
Epididymis helps in storage, nutrition and physiological maturation of sperms. It also aids motility to sperms.

Question 8.
Give the names and functions of the hormones involved in the process of spermatogenesis. Write the names of the endocrine glands from where they are released.
Answer:
The name of hormones, its endocrine glands and functions of the hormones involved in the process of spermatogenesis are given in the following table:

Question 9.
The mother germ cells are transformed into a mature follicle through series of steps. Provide the missing steps in the blank boxes.

Answer:

Question 10.
During reproduction, the chromosome number (2n) reduces to half (n) in the gametes and again the original number (2n) is restored in the offspring. What are the processes through which these events take place?
Answer:
Chromosome number is reduced to half (n) during the process of gametogenesis, and it is again restored to (2n) as a result of fertilisation.

Question 11.
What is the difference between a primary oocyte and a secondary oocyte?
Answer:
Primary oocyte is a diploid structure surrounded by single layer of follicular  through mitosis and differentiation. Secondary oocyte is a hapoid structure and is surrounded by a few layer of granular cells and theca. It is formed from primary oocyte after it undergoes first meiotic division.

Question 12.
What is the significance of ampullary-isthmic junction in the female reproductive tract?
Answer:
Ampullary-isthmic junction of oviduct is a site for fertilisation.

Question 13.
How does zona pellucida of ovum help in preventing polyspermy?
Answer:
During fertilisation, a sperm comes in contact with zona pellucida layer of ovum and induces changes in the membrane known as cortical reaction. This blocks the entry of additional sperms (polyspermy) and maintains monospermy.

Question 14.
Mention the importance of LH surge during menstrual cycle.
Answer:
Rapid secretion of LH leading to its maximum level during mid cycle is known as LH surge. It induces rupture of Graafian follicle and release of ovum (ovulation).

Question 15.
Which type of cell division forms spermatids from the secondary spermatocytes?
Answer:
Secondary spermatocytes undergo meiosis II to form spermatids. Secondary spermatocytes and spermatid both are haploid and this meiosis II is known as equational division.

Short Answer Type Questions

Question 1.
A human female experiences two major changes, menarche and menopause during her life. Mention the significance of both the events.
Answer:
The first menstrual cycle in females is known as menarche. It indicates the attainment of sexual maturity and puberty stage in females. It signifies the maturation and readiness of the female reproductive system for child bearing. It occurs usually at the age of 10-14 years.Menopause is the period of end of cyclic change in females. It indicates the end of reproductive cycle or fertile period in females. It occurs between 45-55 years of age.

Question 2.
(a) How many spermatozoa are formed from one secondary spermatocyte?
(b) Where does the first cleavage division of zygote take place?
Answer:
(a) A secondary spermatocyte gives rise to two spermatids, which get  transformed into two spermatozoa.
(b) First cleavage division of zygote takes place in Fallopian tubes of females.

Question 3.
Corpus luteum in pregnancy has a long life. However, if fertilisation does not take place, it remains active only for 10-12 days. Explain.
Answer:
Zygote formed after fertilisation gets implanted in the inner lining of uterus, called endometrium. Neural signals are conducted to hypothalamus to sustain LH secretion. This helps in maintaining corpus luteum and continue the secretion of progesterone during gestation period. But when fertilisation does not take place, neural signals are not sent to hypothalamus. As a result corpus luteum starts degenerating and can stay alive only for 10-12 days.

Question 4.
What is foetal ejection reflex? Explain how it leads to parturition?
Answer:
Foetal ejection reflex are the uterine contractions induced by fully developed foetus and placenta which signals for parturi­tion.
This stimulates the posterior pituitary of the mother to release oxytocin. Oxytocin causes stronger uterine contractions of smooth muscles of myometrium called labour pains, which further stimulate more secretion of oxytocin. The stimulatory reflex  continues resulting in stronger and stronger contractions and leading to expulsion of the baby (parturition) through birth canal.

Question 5.
Except endocrine function, what are the other functions of placenta?
Answer:
Functions of placenta other than endocrine functions are:

1. Nutritive organ – Food materials pass from the mother’s blood into the foetal blood through the placenta.
2. Digestive organ – The trophoblast of the placenta digests (breaks down) proteins before passing them into the foetal blood.
3. Respiratory organ – Oxygen diffuses from the maternal blood into the foetal blood through the placenta. Carbon dioxide diffuses from the foetal blood into the maternal blood also through the placenta for elimination by the mother’s lungs. Foetal haemoglobin has a greater affinity for oxygen than adult haemoglobin.
4. Excretory organ – Nitrogenous wastes, such as urea, pass from the foetal blood into the maternal blood via placenta for elimination by mother’s kidneys.
5. Storage organ – The placenta stores glycogen for the foetus before liver is formed.
6. Barrier – Placenta serves as an efficient barrier and allows those materials to pass into the foetal blood that are necessary.

Question 6.
Why doctors recommend breast feeding during initial period of infant growth?
Answer:
Human milk consists of water, minerals, fats, proteins and sugar necessary for development of the child. The milk produced’ during initial days of lactation is called colostrum. It is rich in proteins (lactalbumin and lactoprotein) and various other nutrients. It also contains certain antibodies (IgA), which provide passive immunity to the baby.

Question 7.
What are the events that take place in the ovary and uterus during follicular phase of the menstrual cycle.
Answer:
(1) Changes inside the ovary during follicular phase :-

• Primary follicle gets transformed into Graafian follicle.
• Increase in level of estrogen

(2) Changes in uterus during follicular phase :-

• Proliferation of endometrium.
• Endometrium becomes highly vascular and glandular.

Question 8.
Given is a flow chart showing ovarian changes during menstrual cycle. Fill in the spaces giving the name of the hormones responsible for events shown.

Answer:
a – FSH and LH
b – LH
c – Progesterone

Question 9.
Give a schematic labelled diagram to represent oogenesis (without descriptions).
Answer:

Question 10.
What are the changes in the oogonia during the transition of a primary follicle to Graafian follicle?
Answer:
Oogonia divide by mitosis forming primary oocyte which then gets surrounded by a layer of granulosa cells to form primary follicle. The primary follicles are surrounded by more layers of granulosa cells called secondary follicles.The secondary follicle soon changes into a tertiary follicle which is characterised by a fluid filled cavity called follicular antrum. The tertiary follicle is further converted into mature follicle or Graafian follicle. The formation of Graafian follicle through various stages is called folliculogenesis.

Long Answer Type Questions

Question 1.
What role does pituitary gonadotropins play during follicular and ovulatory phases of menstrual cycle? Explain the shifts in steroidal secretions.
Answer:
The menstrual cycle consists of four phases: menstrual phase, follicular phase (proliferative phase), ovulatory phase and secretory phase. Hormonal control during follicular phase:

• FSH from pituitary transforms the primary follicle into Graafian follicle.
• FSH also stimulates Graafian follicular cells to secrete estrogen.
• Estrogen causes proliferation of endo­metrium of the uterine wall.

Hormonal control during ovulatory phase :

• Pituitary glands are stimulated by estrogen to release LH.
• LH surge (maximum level of LH) causes ovulation from the ovary on 14^th day of menstruation cycle. LH also induces transformation of Graafian follicle into corpus luteum, inside the ovary. LH stimulates corpus luteum to secrete progesterone to help implantation,placentation, and maintenance of pregnancy.
• In menstrual phase, there is reduction of progesterone and estrogen. Gonado­tropin releasing hormone (GnRH) stimulates the release of FSH and LH. FSH stimulates the ovarian follicles to produce estrogens during proliferative phase. LH stimulates the ovulation in ovulatory phase.
• LH develops corpus luteum which causes increased production of progesterone in secretory phase.

Question 2.
Meiotic division during oogenesis is different from that in spermatogenesis. Explain how and why?
Answer:
Primary spermatocyte divides by meiosis I to form two secondary spermato­cytes. Primary oocyte undergoes meiosis I to form one secondary oocyte and one polar body.
Secondary spermatocyte divides by meiosis II to produce two spermatids. Secondary oocyte divides by meiosis II to form one ovum and one polar body.
A spermatocyte forms four spermatozoa. An oocyte forms only one egg or ovum. Unequal cell divisions during oogenesis, makes the ovum much larger than the other three polar bodies. Ovum has more cytoplasm and more organelles, it has a better chances of surviving. The male makes million of tiny sperms while, the female makes one egg per month because the sperms have to search for the eggs and only a few succeed in this task.

Question 3.
The zygote passes through several developmental stages till implantation. Describe each stage briefly with suitable diagrams.
Answer:

1. The zygote moves from isthmus to uterus and undergo mitotic divisions called cleavage divisions.
2. It forms 2, 4, 6, 8,16 daughter cells, called  blastomeres.
3. The embryo with 8-16 blastomeres is called morula.
4. The morula continues to get transformed into blastocyst.
5. The blastomeres in the blastocyst are arranged into an outer layer called trophoblast, and an inner group of cells attached to trophoblast called inner cell mass.
6. The trophoblast layer gets attached to the endometrium and inner cell mass gets differentiated as the embryo.
7. After attachment uterine cells divide rapidly and cover the blastocyst.
8. As a result the blastocyst becomes embedded in the endometrium of the uterus.
9. This is known as implantation, and it leads to pregnancy.
   

Question 4.
Draw a neat diagram of thefemale reproductive system and label the parts associated with the following (a) production of gamete, (b) site of fertilisation(c) site of implantation and, (d) birth canal.
Answer:

Question 5.
With a suitable diagram, describe the organisation of mammary gland.
Answer:
Mammary glands are paired structures consisting of glandular tissue, the fibrous tissue and variable amount of fat. They are compound tubulo-alveolar modified sweat glands. The glandular tissue of breast consists of about 15-20 lobes of milk glands. Each lobe is formed of many lobules containing cluster of cells called alveoli. The cells of alveoli secrete milk, which is stored in the lumen (cavities) of alveoli. The alveoli open into mammary  tubules, the tubules of each lobe join to form a mammary duct. Several mammary ducts join to form a wider mammary ampulla, which is connected to lactiferous duct, through which milk is sucked out. Mammary glands are functional in females and vestigial in males. Breasts in females are small sized upto puberty. The size increases after puberty under stimulation of estrogen. It further increases during pregnancy and after child birth under the stimulation of prolactin and progesterone.

We hope the NCERT Exemplar Solutions for Class 12 Biology chapter 3 Human Reproduction help you. If you have any query regarding NCERT Exemplar Solutions for Class 12 Biology chapter 3 Human Reproduction, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Solutions for Class 12 Biology chapter 2 Sexual Reproduction,in Flowering Plants

These Solutions are part of NCERT Exemplar Solutions for Class 12 Biology. Here we have given NCERT Exemplar Solutions for Class 12 Biology chapter 2 Sexual Reproduction,in Flowering Plants

Multiple Choice Questions

Question 1.
Among the terms listed below, those that are not technically correct names for a floral whorl are
(a) androecium
(b) corolla|
(c) (i) and (iv)
(d) (ii) and (iv)
Answer:
(c) : The technically correct terms for the floral whorls are (from outermost to innermost) calyx, corolla, androecium and gynoecium. They are made up of sepals, petals, stamens and carpels, respectively.

Question 2.
Embryo sac is to ovule as________ is to an anther.
(a) stamen
(b) filament
(c) pollen grain   
(d) androecium
Answer:
(c) : A typical carpel consist of ovary which can have many ovules. Each ovule has an embryo sac, which in turn has a single egg cell. Similarly, in majority of angiosperms each stamen consists of a bilobed anther, which in turn has two pollen sacs in each lobe, consisting of pollen grains.

Question 3.
In a typical complete, bisexual and hypogynous flower the arrangement of floral whorls on the thalamus from the outermost to the innermost is
(a) calyx, corolla, androecium and gynoecium
(b) calyx, corolla, gynoecium and androecium|
(c) gynoecium, androecium, corolla and calyx
(d) androecium, gynoecium, corolla and calyx.
Answer:
(a)

Question 4.
A dicotyledonous plant bears flowers but never produces fruits and seeds. The most probable cause for the above situation is
(a) plant is dioecious and bears only pistillate flowers
(b) plant is dioecious and bears both pistillate and staminate flowers
(c) plant is monoecious
(d) plant is dioecious and bears only staminate flowers.
Answer:
(d) : Fruits can develop from a single ovary of a single flower (simple fruit) or from several free carpels of a single flower (aggregate) or from whole inflorescence (multiple). In total, fruits develop from ovaries. This is why, a dioecious plant (unisexual) bearing only staminate (male) flowers will not produce fruits, whereas monoecious plants (bisexual) or dioecious plants bearing only pistillate (female) flowers or pistillate and staminate both can bear fruits (pollination).

Question 5.
The outermost and innermost wall layers of microsporangium in an anther are respectively
(a) endothecium and tapetum
(b) epidermis and endodermis
(c) epidermis and middle layer
(d) epidermis and tapetum.
Answer:
(d) : The wall layers of a micro­sporangium from outermost to innermost are : epidermis, endothecium, middle layers and tapetum. The first three layers generally provide protection and help in dehiscence of anther. Tapetum performs nutritive function for pollen grains.

Question 6.
During microsporogenesis, meiosis occurs in
(a) endothecium
(b) microspore mother cells
(c) microspore tetrads
(d) pollen grains.
Answer:
(b) : Microsporogenesis is the formation of microspores in the form of tetrads, which later separate and are called pollen grains. Microspore mother cell (2n) undergoes meiosis for the formation of haploid pollen grains formed first in the form of spore tetrads.

Question 7.
From among the sets of terms given below, identify those that are associated with the gynoecium.
(a) Stigma, ovule, embryo sac, placenta
(b) Thalamus, pistil, style, ovule
(c) Ovule, ovary, embryo sac, tapetum
(d) Ovule, stamen, ovary, embryo sac
Answer:
(a) : Stigma,is a part of pistil on which pollen grain lands. Each ovary may have many ovules, which have embryo sacs in them. Placenta is a tissue inside ovary to which ovules are attached. Thalamus is the terminal part of the axis of flower which bears all floral appendages. Tapetum is the innermost layer of microsporangium while stamen is component of androecium.

Question 8.
Starting from the innermost part, the correct sequence of parts in an ovule are
(a) egg, nucellus, embryo sac, integument
(b) egg, embryo sac, nucellus, integument
(c) embryo sac, nucellus, integument, egg
(d) egg, integument, embryo sac, rtucellus.
Answer:
(b) : Egg cell is inside the embryo sac in the ovule. The embryo sac is further enclosed by the parenchymatous tissue, nucellus, which later provides nutrition to developing embryo. Nucellus is ultimately surrounded by integuments.

Question 9.
From the statements given below choose the option that are true for a typical female gametophyte of a flowering plant.
(1) It is 8-nudeate and 7-celled at maturity.
(2) It is free-nuclear during the development.
(3) It is situated inside the integument but outside the nucellus.
(4) It has an egg apparatus situated at the chalazal end.
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (ii)   
(d) (ii) and (iv)
Answer:
(c) : Female gametophyte or embryo ‘* sac is present in the nucellus of an ovule. It is formed by free nuclear mitotic divisions of megaspore which forms 8 nucleate structure (4 nuclei each at micropylar and chalazal end). One nucleus from each side moves to the middle to form polar nuclei which later on fuse to form secondary nucleus. The remaining three nuclei at each end get surrounded by wall to form cells. Hence, female gametophyte is 8-nucleate and 7-celled at maturity because of presence of secondary nucleus. Egg apparatus is situated at the micropylar end whereas 3 antipodal s are situated at chalazal end.

Question 10.
Autogamy can occur in a chasmogamous flower if
(a) pollen matures before maturity of ovule
(b) ovules mature before maturity of pollen
(c) both pollen and ovules mature simultaneously
(d) both anther and stigma are of equal lengths.
Answer:
(c) : Autogamy is pollination within a flower, chasmogamous flowers are those in which anthers and stigma are exposed. For autogamy, in such a flower to take place, pollen and ovule should mature simultaneously and anther and stigma should lie close to each other.

Question 11.
Choose the correct statement from the following.
(a) Cleistogamous flowers always exhibit autogamy.
(b) Chasmogamous flowers always exhibit geitonogamy.
(c) Cleistogamous flowers exhibit both autogamy and geitonogamy.
(d) Chasmogamous flowers never exhibit autogamy.
Answer:
(a) : Autogamy is pollination within the same flower. Geitonogamy is pollination between different flowers of same plant. Xenogamy is pollination between flowers of different plants of same species. Cleistogamous flowers (that do not open at all) always exhibit autogamy, where as chasmogamous flowers (with exposed anthers and stigma) can exhibit autogamy, geitonogamy or xenogamy.

Question 12.
A particular species of plant produces light, non-sticky pollen in large numbers and its stigmas are long and feathery. These modifications facilitate pollination by
(a) insects
(b) water
(c) wind
(d) animals
Answer:
(c) : Light, non-sticky pollens produced in large numbers are generally traits of wind pollinated (anemophilous) plants. Insect and animal pollinated plants have sticky pollens. Long and feathery stigma is also characteristic of anemophilous plants. Maize, Cannabis and many grasses are some of the examples of this category.

Question 13.
From among the situations given below, choose the one that prevents both autogamy and geitonogamy.
(a) Monoecious plant bearing unisexual flowers.
(b) Dioecious plant bearing only male or female flowers.
(c) Monoecious plant with bisexual flowers.
(d) Dioecious plant with bisexual flowers.
Answer:
(b) : Monoecious plant (bisexual) bearing either bisexual or unisexual flowers can exhibit both autogamy as well as geitonogamy. Dioecious (unisexual) plants bearing only male or female flowers will not show autogamy or geitonogamy hence, only xenogamy is possible.

Question 14.
In a fertilised embryo sac, the haploid, diploid and triploid structures are
(a) synergid, zygote and primary endosperm nucleus
(b) synergid, antipodal and polar nuclei
(c) antipodal, synergid and primary endo­sperm nucleus
(d) synergid, polar nuclei and zygote.
Answer:
(a) : Double fertilisation is the fusion of two male gametes brought by a pollen tube with two different cells of the same female gametophyte in order to produce two different structures. It is found only in angiosperms where it was first discovered by Nawaschin in 1898 in Fritillaria and Lilium. Out of the two male gametes one fuses with egg or oosphere to perform generative fertilisation. Generative fertilisation is also called syngamy or true fertilisation. It gives rise to a diploid zygote or oospore. The second male gamete fuses with two haploid polar nuclei or diploid secondary nucleus of the central cell to form a triploid primary endosperm nucleus (PEN). This is called as vegetative fertilisation (or triple fusion).

Question 15.
In an embryo sac, the cells that degenerate after fertilisation are
(a) synergids and primary endosperm cell
(b) synergids and antipodals
(c) antipodals and primary endosperm cell
(d) egg and antipodals.
Answer:
(b)

Question 16.
While planning for an artificial hybridisation programme involving dioecious plants, which of the following steps would not be relevant?
(a) Bagging of female flower
(b) Dusting of pollen on stigma
(c) Emasculation
(d) Collection of pollen
Answer:
(c) : Artificial hybridisation is human performed crossing of two different plants having complementary good traits in order to obtain an overall superior variety. Artificial hybridisation has been used by plant breeders for crop improvement programme. Two precautionary measures in artificial hybridisation are emasculation and bagging. Emasculation is removal of stamens from the floral buds of female parent so that chances of self pollination are eliminated. In case of dioecious (unisexual) plants, emasculation is not required.

Question 17.
In the embryos of a typical dicot and a grass, true homologous structures are
(a) coleorhiza and coleoptile
(b) coleoptile and scutellum
(c) cotyledons and scutellum
(d) hypocotyl and radicle.
Answer:
(c) : During the development of dicot embryo, initially the dicot embryo is globular and undifferentiated. Early embryo with radial symmetry is called proembryo. It is transformed into embryo with the development of radicle, plumule and cotyledons. Two cotyledons differentiate from the sides with a faint plumule in the centre. At this time the embryo becomes heart-shaped. Part of embryo axis between the plumule and cotyledonary node is epicotyl (above the level of cotyledons) while the part between radicle and cotyledonary node is called hypocotyl (below the level of cotyledons). The single cotyledon of monocotyledonous seed (e.g. maize grain) is called scutellum. It occupies the major portion of the embryo regions of grain.

Question 18.
The phenomenon observed in some plants wherein parts of the sexual apparatus is used for forming embryos without fertilisation is called
(a) parthenocarpy
(b) apomixis
(c) vegetative propagation
(d) sexual reproduction.
Answer:
(b) : Apomixis is the term given to any phenomenon that leads to formation of embryo wherein parts of the sexual apparatus are used, but without fertilisation. Fertilisation is also absent in vegetative propagation, but parts of sexual apparatus are not involved. An example of apomixis is Citrus.

Question 19.
In a flower, if the megaspore mother cell forms megaspores without undergoing meiosis and if one of the megaspores develops into an embryo sac, its nuclei would be 
(a) haploid
(b) diploid
(c) a few haploid and a few diploid
(d) with varying ploidy.
Answer:
(b)

Question 20.
The phenomenon wherein, the ovary develops into a fruit without fertilisation is called
(a) parthenocarpy
(b) apomixis
(c) asexual reproduction
(d) sexual reproduction.
Answer:
(a) : Fertilised ovary is technically called fruit. But if ovary develops into fruit, without fertilisation, it is called parthenocarpic fruit. Such fruits are generally seedless. Some common examples found in nature are : Citrus, banana, etc. Parthenocarpy can also be artificially induced by the application of certain plant hormones, specially, auxin and gibberellins.

Very Short Answer Type Questions

Question 1.
Name the component cells of the ‘egg apparatus’ in an embryo sac.
Answer:
Egg apparatus consists of two synergids and one egg cell.

Question 2.
Name the part of gynoecium that determines the compatible nature of pollen grain.
Answer:
Stigma is that part of gynoecium which determines the compatible nature of pollen grain.

Question 3.
Name the common function that cotyledons and nucellus perform.
Answer:
Common function of nucellus and cotyledons is to provide nourishment.

Question 4.
Complete the following flow chart:

Answer:

Question 5.
Indicate the stages where meiosis and mitosis occur (1, 2 or 3) in the flow chart.
Megaspore mother cell ——-1—— > Megaspores –2— > Embryo sac —-3—- > Egg
Answer:
1 = Meiosis 2 = Mitosis 3 = Mitosis
In the diagram given below, show the path of a pollen tube from the pollen on the stigma into the embryo sac. Name the components of egg apparatus

Question 6.
In the diagram given below, show the path of a pollen tube from the pollen on the stigma into the embryo sac. Name the components of egg apparatus.

Answer:

Egg apparatus consists of two synergids and one egg cell.

Question 7.
Name the parts of pistil which develop into fruit and seeds.
Answer:
Fruit develops from ovary and seeds develop from ovules of a pistil.

Question 8.
In case of polyembryony, if an embryo develops from the synergid and another from the nucellus, which is haploid and which is diploid?
Answer:
In case of polyembryony, if an embryo develops from synergid, it will be haploid and if it develops from nucellus, it will be diploid.

Question 9.
Can an unfertilised, apomictic embryo sac give rise to a diploid embryo? If yes, then how?
Answer:
Apomictic embryo sac develops without the involvement of meiosis and syngamy. Here, a diploid embryo is formed from diploid egg cell or from some other diploid cell of embryo sac.

Question 10.
Which are the three cells found in a pollen grain when it is shed at the three celled stage?
Answer:
The three cells found in a pollen grain when it is shed at the three celled stage are two male gametes and one vegetative cell.

Question 11.
What is self-incompatibility?
Answer:
If a pistil carrying functional female gametes fails to set seeds following pollination with viable and fertile pollen, capable of bringing about fertilisation in another pistil, the two are said to be incompatible, and the phenomenon is known as sexual incompatibility. Sexual incompatibility may be interspecific (between individuals of different species) or intraspecific (between individuals of the same species). The latter is also called self-incompatibility.

Question 12.
Name the type of pollination in self­ incompatible plants.
Answer:
Self incompatible plants do not undergo self pollination. They can undergo only cross pollination.

Question 13.
Draw the diagram of a mature embryo sac and show its 8-nudeate, 7-celled nature. Show the following parts: antipodals, synergids, egg, central cell, polar nuclei.
Answer:

Question 14.
Which is the triploid tissue in a fertilised ovule? How is the triploid condition achieved?
Answer:
Endosperm is the triploid tissue in a fertilised ovule which is formed by the division of Primary Endosperm Nucleus (PEN). PEN is formed by the fusion of one male gamete (haploid) with secondary nucleus (diploid) hence, it is triploid.

Question 15.
Are pollination and fertilisation necessary in apomixis? Give reasons.
Answer:
In apomixis, there is no need of pollination and fertilisation. Embryo can develop directly from the nucellus or synergid or egg cell.

Question 16.
Identify the type of carpel with the help of diagrams given below:
Answer:

(a) Polycarpellary syncarpous
(b) Polycarpellary apocarpous

Question 17.
How is, pollination carried out in water plants?
Answer:
Plants which occur below the water level undergo epihydrophily or hypohydrophily,i.e pollination takes place by the agency of water. Aquatic plants which are emerged or present at the water surface can undergo entomophily, anemophily or epihydrophily.

Question 18.
What is the function of the two male gametes produced by each pollen grain in angiosperms?
Answer:
The function of the two male gametes produced by each pollen grain in angiosperms are as follows:

1. One of the male gamete fuses with egg cell to produce zygote (2n).
2. Second male gamete fuses with two polar nuclei/diploid secondary nucleus to form primary endosperm nucleus (3n)

Short Answer Type Questions

Question 1.
List three strategies that a bisexual chasmogamous.flower can evolve to prevent self pollination (autogamy).
Answer:
Strategies that a bisexual chasmogamous flower can evolve to prevent self pollination are as follows:

1. Pollen release and stigma receptivity is not synchronised. Either the pollen is released before stigma is receptive or stigma becomes receptive much before pollen release.
2. Anther and stigma are placed at different positions, so that pollen cannot come in contact with stigma.
3. When the pollen of the flower reach the stigma of the same flower, pollen grains
4. do not germinate and the phenomenon is called self-incompatibility.

Question 2.
Given below are the events that are observed in an artificial hybridisation programme. Arrange them in the correct sequential order in which they are followed in the hybridisation programme.
(a) Re-bagging
(b) Selection of parents
(c) Bagging
(d) Dusting the pollen on stigma
(e) Emasculation
(f) Collection of pollen from male parent.
Answer:
(b) —> (e) —> (c) —> (f) —> (d) —> (a)

Question 3.
Vivipary automatically limits the number of offsprings in a litter. How?
Answer:
Viviparity is a form of reproduction in animals in which the development of embryos takes place within the mother’s/ female parent’s body. The embryo obtains its nourishment directly from mother via placenta or by other means and subsequently mother gives birth to the full term young one. It is common in most mammals. Viviparity limits the number of offspring in a litter due to the following reasons:

1. As the number of eggs released during ovulation are limited during oestrous or menstrual cycles so the number of eggs fertilised during reproductive cycle of female are also limited.
2. As the entire period of development called gestation is passed within the mother’s/female parent’s body; it restricts the number of embryo that can develop together at one time.
3. During gestation no ova or egg are released.

Question 4.
Does self incompatibility impose any restrictions on autogamy? Give reasons and suggest the method of pollination in such plants.
Answer:
Self incompatibility is the phenomenon in which self pollens fail to germinate on stigma of pistil. It is a gene physiological process which is controlled by single gene S. If pollen and pistil will have the S alleles in common, pollens will not be functional on that pistil. As self pollens will have common S alleles with pistil (of the same flower), self pollination (autogamy) cannot take place in self incompatible plants. Cross pollens on the other hand, will not have common S alleles with pistil and hence, cross pollination can easily take place in such plants.

Question 5.
In the given diagram, write the names of parts shown with lines.

Answer:

Question 6.
What is polyembryony and how can it be commercially exploited?
Answer:
The phenomenon of having more than one embryo is called polyembryony, e.g., onion, groundnut.

Polyembryony is practically important because genetically uniform parental type seedlings are obtained from nucellar embryos. Nucellar embryos are superior to those obtained by vegetative propagation because nucellar embryo seedlings are disease free and maintain their superiority for long time.

Question 7.
Are parthenocarpy and apomixis different phenomena? Discuss their benefits.
Answer:
Parthenocarpy is production and development of seedless fruits. Apomixis is a type of sexual reproduction which does not involve meiosis and syngamy and produces seeds without fertilisation.
Benefits of parthenocarpy are as follows:
(1) It produces fruits which do not contain irritant seeds.
(2) Processing of fruits by food industry requires the removal of seeds which is quite difficult. Therefore, seedless fruits are preferred by food industry.
(3) Fruits can be developed inside green houses where pollinators are not available.
Benefits of apomixis are as follows:

• Production of hybrid seeds is costly and hence the cost of hybrid seeds becomes too expensive for the farmers. If these hybrids are made into apomicts, there is no segregation of characters in the hybrid progeny. Then the farmers can keep on using the hybrid seeds to raise new crop year after year and do not have to buy hybrid seeds every year.
• Adventive embryos are better clones than cuttings.
• Embryos formed through apomixis are generally free from infections.

Question 8.
Why does the zygote begin to divide only after the division of primary endosperm cell (PEC)?
Answer:
Endosperm development precedes embryo development. The primary endo¬sperm cell divides repeatedly and forms the triploid endosperm tissue. The cells of this tissue are filled with reserve food materials and are used for the nutrition of the developing embryo at the micropylar end of the embryo sac. This is an adaptation to provide assured nutrition to the developing embryo.

Question 9.
The generative cell of a two-celled pollen divides in the pollen tube but not in a three- celled pollen. Give reasons.
Answer:
In some plants pollen grains are shed at 2 celled stage whereas in others pollen grains are shed at 3 celled stage. The pollens which are shed at 2 celled stage contain vegetative cell and a generative cell. At the time of pollen germination, generative cell divides to form two male gametes in the pollen tube.
On the other hand, in case of pollens which are shed at 3 celled stage, the generative cell has already divided to form two male gametes before pollination or pollen germination, i.e., formation of pollen tube.

Question 10.
In the ,figure given below, label the following parts: .
Male gametes, egg cell, polar nuclei, synergid and pollen tube.

Answer:

Long Answer Type Questions

Question 1.
Starting with the zygote, draw the diagrams of the different stages of embryo development in a dicot.
Answer:

Question 2.
What are the possible types of pollinations in chasmogamous flowers. Give reasons.
Answer:
Chasmogamous flowers are the flowers with stamens and stigma exposed .They may undergo self pollination or cross pollination.
(1) Self pollination in chasmogamous flowers : Bisexual flowers where stigma and the stamens both mature almost at the same time can undergo autogamy or geitonogamy.

• Autogamy – Transfer of pollen grains from anther of a flower to the stigma of the same flower.
• Geitonogamy – When pollen grains from one flower are deposited on the stigma of another flower borne on the same plant.

(2) Cross pollination in chasmogamous flowers : Transfer of pollen grains from anther of a flower to the stigma of different flower growing on different plant of same species. Cross pollination is carried by various abiotic agents like wind and water or by biotic agents like insects, birds and animals etc.

Question 3.
With a neat, labelled diagram, describe the parts of a mature angiosperm embryo sac. Mention the role of synergids.
Answer:
Neat and labelled diagram of mature angiospermic embryo sac is as follows :

Ovule is an integumented megasporangium that encloses an embryo sac. Common type of ovule is anatropous. Parts of mature angiospermic ovule are:
(1) Funicle : It is the stalk of the ovule. It is attached to placenta by funicle. In anatropous ovules the funicle is fused with the body of the ovule lengthwise to form raphe. Place of union of funicle and the body of ovule is called hilum.

(2) Integuments : They are one or two cuticularised coverings of the ovule. The  place of origin of integuments is called chalaza. A pore’occurring on one side of ovule where integuments are absent is known as micropyle.

(3)  Nucellus : It is parenchymatous tissue  contained in the ovule.

(4) Embryo sac : It is female gametophyte which is covered by a thin membrane. Embryo sac has seven cells. Three cells form egg apparatus towards micropylar end. There are two synergids and one egg or oosphere in the egg apparatus. Three cells on the opposite side are called antipodal cells. The seventh cell of the embryo sac is the largest cell called central cell. Central cell has two polar nuclei which may fuse to form a diploid secondary nucleus. Synergids are short­lived (one of them degenerates long before fertilisation and second after entry of pollen tube into embryo sac).
These synergids help :

• In growth of pollen tube towards egg by secreting chemotropically active substances.
• In nutrition of embryo sac by absorption and transport of food from nucellus through their filiform apparatus.

Filiform apparatus in the form of finger like projections from cell wall is present in upper part of each synergid. The filiform apparatus is useful for the absorption and transportation of

materials from the nucellus to the embryo sac. Hook like structures help in easy penetration of pollen tube and liberation of male gamete from the pollen tube.

Question 4.
Draw the diagram of a microsporangium and label its wall layers. Write briefly on the role of the endothecium.
Answer:

Question 5.
Endothecium protects the sporogenous tissue and helps in dehiscence of pollen grains.
Embryo sacs of some apomictic species appear normal but contain diploid cells. Suggest a suitable explanation for the condition.
Answer:
Embryo sacs of some apomictic species appear normal but contain diploid cells, because embryo sacs either develop from diploid nucellar cells or from diploid megaspore mother cells without undergoing meiosis. It leads to formation of apomictic diploid embryos.

We hope the NCERT Exemplar Solutions for Class 12 Biology chapter 2 Sexual Reproduction,in Flowering Plants help you. If you have any query regarding NCERT Exemplar Solutions for Class 12 Biology chapter 2 Sexual Reproduction,in Flowering Plants, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Solutions for Class 12 Biology chapter 1 Reproduction in Organisms

These Solutions are part of NCERT Exemplar Solutions for Class 12 Biology. Here we have given NCERT Exemplar Solutions for Class 12 Biology chapter 1 Reproduction in Organisms

Multiple Choice Questions

Question 1.
A few statements describing certain features of reproduction are given below.
(i) Gametic fusion takes place.
(ii) Transfer of genetic material takes place.
(iii) Reduction division takes place.
(iv) Progeny have some resemblance with parents.
Select the options that are true for both asexual and sexual reproduction from the options given below.
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (ii) and (iv)
(d) (i) and (iii)
Answer:
(c) : Reproduction is a biological process in which-an organism produces young ones (offspring) similar to itself. In reproduction, offsprings have some resemblance with parents. Both sexual and asexual reproduction involve transfer of genetic material.

Question 2.
The term ‘clone’ cannot be applied to offspring formed by sexual reproduction because
(a) offspring do not possess exact copies of parental DNA
(b) DNA of only one parent is copied and passed on to the offspring
(c) offspring are formed at different times
(d) DNA of parent and offspring are completely different.
Answer:
(a) : In sexual reproduction, there is fusion of male gametes and female gametes, the offspring produced are not identical to their parents. This genetic recombination leads to variations, which play an important role in evolution.

Question 3.
A sexual method of reproduction by binary fission is common to which of the following?
(i) Some eukaryotes
(ii) All eukaryotes
(iii) Some prokaryotes
(iv) All prokaryotes
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (iii) and (iv)
Answer:
(c)

Question 4.
A few statements with regard to sexual reproduction are given below.
(i) Sexual reproduction does not always require two individuals.
(ii) Sexual reproduction generally involves gametic fusion.
(iii) Meiosis never occurs during sexual reproduction.
(iv) External fertilisation is a rule during sexual reproduction.
Choose the correct statements from the options below.
(a) (i) and (iii)
(b) (i) and (ii)
(c) (ii) and (iii)
(d) (i) and (iv)
Answer:
(b) : Meiosis is required for the production of haploid gametes during sexual reproduction. External fertilisation is not a rule during sexual reproduction, it can occur internally also.

Question 5.
A multicellular, filamentous alga exhibits a type of sexual life cycle in which the meiotic division occurs after the formation of zygote. The adult filament of this alga has
(a) haploid vegetative cells  and   diploid gametangia
(b) diploid vegetative cells  and   diploid gametangia
(c) diploid vegetative cells  and  haploid gametangia
(d) haploid vegetative cells and  haploid gametangia.
Answer:
(d)

Question 6.
The male gametes of rice plant have 12 chromosomes in their nucleus. The chromo­some number in the female gamete, zygote and the cells of the seedling will be, respectively
(a) 12,24,12
(b) 24,12,12
(c) 12,24,24  
(d) 24,12,24.
Answer:
(c) : Chromosome number in male gamete of rice plant is n = 12 therefore chromosome number in female gamete would also be 12. Zygote is diploid as it is the product of fertilisation and the cells of the seedling would be meiocytes and other diploid cells. Hence, the chromosome number in both zygote and cells of seedling will be 2n = 24.

Question 7.
Given below are a few statements related to external fertilisation. Choose the correct statements.
(i) The male and female gametes are formed and released simultaneously.
(ii) Only a few gametes are released into the medium.
(iii) Water is the medium in a majority of organisms exhibiting external fertilisa­tion.
(iv) Offspring formed as a result of external fertilisation have better chance of survival than those formed inside an organism.
(a) (iii) and (iv)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (i) and (iv)
Answer:
(b) : A large number of gametes are released into the medium to increase the chances of fertilisation. The chances of survival of offsprings from external fertilisation are lesser than those of internal fertilisation as they face more risk from predators.

Question 8.
The statements given below describe certain features that are observed in the pistil of flowers.
(i) Pistil may have many carpels.
(ii) Each carpel may have more than one ovule.
(iii) Each carpel has only one ovule.
(iv) Pistil have only one carpel.
Choose the statements that are true from the options below.
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)
Answer:
(a) : Gynoecium is the female part of the flower, a unit of which is called pistil. A pistil may have one or more than one carpels (monocarpellary, bicarpellary etc). Each carpel may have more than one ovules.

Question 9.
Which of the following situations correctly describe the similarity between an angiosperm egg and a human egg?
(i) Eggs of both are formed only once in a lifetime.
(ii) Both the angiosperm egg and human egg are stationary.
(iii) Both the angiosperm egg and human egg are motile transported.
(iv) Syngamy in both results in the formation of zygote.
Choose the correct answer from the options given below.
(a) (ii) and (iv)
(b) (iv) only
(c) (iii) and (iv)
(d) (i) and (iv)
Answer:
(b) : Syngamy is the complete and permanent fusion of male and female gametes to form a zygote.

Question 10.
Appearance of vegetative propagules from the nodes of plants such as sugarcane and ginger is mainly because
(a) godes are shorter than internodes
(b) nodes have meristematic cells
(c) nodes are located near the soil
(d) nodes have non-photosynthetic cells.
Answer:
(b) : Vegetative propagation is asexual reproduction from ‘various parts in plants. In plants, such as, sugarcane and ginger, appearance of vegetative propagules from nodes is because of presence of meristematic cells in them. Meristematic cells have the ability to divide to form new cells which can differentiate and give rise to permanent tissues.

Question 11.
Which of the following statements, support the view that elaborate sexual reproductive process appeared much later in the organic evolution?
(i) Lower groups of organisms have simpler body design.
(ii) Asexual reproduction is common in lower groups.
(iii) Asexual reproduction is common in higher groups of organisms.
(iv) The high incidence of sexual reproduction in angiosperms and vertebrates.
Choose the correct answer from the options given below.
(a) (i), (ii) and (iii)
(b) (i), (iii) and (iv)
(c) (i), (ii) and (iv) 
(d) (ii), (iii) and (iv)
Answer:
(c)

Question 12.
Offspring formed by sexual reproduction exhibit more variation than those formed by asexual reproduction because
(a) sexual reproduction is a lengthy process
(b) gametes of parents have qualitatively different genetic composition
(c) genetic material comes from parents of two different species.
(d) greater amount of DNA is involved in sexual reproduction.
Answer:
(b) : Sexual reproduction occurs in almost all types of animals and mostly in higher plants. It is usually biparental. Daughter organisms genetically differ from the parents. Since there are variations, so it contributes to evolution of the species.

Question 13.
Choose the correct statement from amongst the following.
(a) Dioecious organisms are seen only in animals.
(b) Dioecious organisms are seen only in plants.
(c) Dioecious organisms are seen in both plants and animals.
(d) Dioecious organisms are seen only in vertebrates.
Answer:
(c) : Dioecious organisms are those in which male and female sex organs are present in different organisms, where as monoecious organisms are those in which male and female sex organs are present in the same organism. Monoecious organisms are also called as hermaphrodite. Dioecious organisms are seen in both plants and animals. Papaya, date palm and most of the animals are dioecious.

Question 14.
There is no natural death in single celled organisms like Amoeba and bacteria because
(a) they cannot reproduce sexually
(b) they reproduce by binary fission
(c) parental body is distributed among the offspring
(d) they are microscopic.
Answer:
(c) : These are no natural death in single celled organisms like Amoeba and bacteria. It is so, because of asexual reproduction, the body of parent is divided into daughter cells. So, in effect, there is no practical death in Amoeba and bacteria.

Question 15.
There are various types of reproduction. The type of reproduction adopted by an organism depends on
(a) the habitat and morphology of the organism
(b) morphology of the organism
(c) morphology and physiology of the organism
(d) the organism’s habitat, physiology and genetic makeup.
Answer:
(d) : There are various types of reproduction, both asexual (fission, budding, etc.) and sexual (internal and external). The type of reproduction, an organism undergoes depends ultimately on its genetic makeup which influences its physiology. Habitat also influences the type of reproduction, that organism undergoes.

Question 16.
Identify the incorrect statement.
(a) In asexual reproduction, the offspring produced are morphologically and genetically identical to the parent.
(b) Zoospores are sexual reproductive structures.
(c) In asexual reproduction, a single parent produces offspring with or without the formation of gametes.
(d) Conidia are asexual structures in
Answer:
(b) : Spores formation is also a type of asexual reproduction. Zoospores, conidia, oidia, etc. are all asexually reproducing structures. There is generally no gamete formation in asexual reproduction and the offsprings produced are called clones.

Question 17.
Which of the following is a post-fertilisation event in flowering plants?
(a) Transfer of pollen grains
(b) Embryo development
(c) Formation of flower
(d) Formation of pollen grains
Answer:
(b) : Events in sexual reproduction after the fertilisation are called post-fertilisation events. After fertilisation, a diploid zygote is formed in all sexually reproducing organisms. The process of development of embryo from the zygote is called embryogenesis.

Question 18.
The number of chromosomes in the shoot tip cells of a maize plant is 20. The number of chromosomes in the microspore mother cells of the same plant shall be
(a) 20 
(b) 10
(c) 40
(d) 15.
Answer:
(a) : Shoot tip cells and microspore mother cells both are diploid in maize plant. If number of chromosomes in shoot tip cell (2n) = 20, then number of chromosomes in microspore mother cell will be (2n) = 20.

Very Short Answer Type Questions

Question 1.
Mention two inherent characteristics of Amoeba and yeast that enable them to reproduce asexually.
Answer:
The two inherent characteristics for asexual reproduction in Amoeba and yeast are :

1. Gametes are not formed in Amoeba and yeast.
2. Uniparental condition (i.e., single parent) is involved in reproduction of both Amoeba and yeast.

Question 2.
Why do we refer to offspring formed by asexual method of reproduction as clones?
Answer:
Offsprings produced by asexual reproduction are morphologically and genetically similar to their parents. Hence, they are known as clones.

Question 3.
Although potato tuber is an underground part, it is considered as a stem. Give two reasons.
Answer:
Reasons for considering potato as a stem are:

1. Differentiation into nodes and inter­nodes.
2. The nodes bear buds which can grow to from leaf shoots or plantlets.

Question 4.
Between an annual and a perennial plant, which one has a shorter juvenile phase? Give one reason.
Answer:
Annual plant have shorter juvenile phase as they complete their life cycle in single season i.e., a few weeks to a few months, e.g., wheat, maize, pea, gram.

Question 5.
Rearrange the following events of sexual reproduction in the sequence in which they occur in a flowering plant : embryogenesis, fertilisation, gametogenesis, pollination.
Answer:
The correct sequence of events of sexual reproduction in flowering plants are as follows : gametogenesis, pollination, fertilisation, embryogenesis.

Question 6.
The probability of fruit set in a self-pollinated bisexual flower of a plant is far greater than a dioecious plant. Explain.
Answer:
Presence of male and female repro­ductive organs on same plant provides more chances of self pollination and therefore increases chances of fruit set. However in dioecious plants agents of pollination are needed which may therefore decrease the chances of a fruit set.

Question 7.
Is the presence of large number of chromosomes in an organism a hindrance to sexual reproduction? Justify your answer by giving suitable reasons.
Answer:
The presence of a large number of chromosomes in an organism is not a hindrance to sexual reproduction.

Question 8.
Is there a relationship between the size of an organism and its life span? Give two examples in support of your answer.
Answer:
There is no direct correlation between the life span of organisms and their sizes.

1. The crow and parrot are nearly of the same size, but life span of crow and parrot are 15 years and 140 years respectively.
2. The mango and the peepal trees are nearly of the same size but the life span of mango and peepal are 100 years and 1000 years respectively.

Question 9.
In the figure given below the plant bears two different types of flowers marked ‘A’ and ‘B’. Identify the types of flowers and state the type of pollination that will occur in them.

Answer:
The plant shown in figure has two types of flowers:
Flower A – chasmogamous type with stigma and anthers exposed. Such type of flowers may undergo self or cross pollination.
Flower B – Cleistogamous type – closed type of flowers, where stigma and anthers are not exposed. Such type of flowers undergo only self pollination.

Question 10.
Give reasons as to why cell division cannot be a type of reproduction in multicellular organisms.
Answer:
In multicellular organisms cell division does not divide the whole body into daughter cells as in unicellular organisms. But multicellular organisms have a well developed reproductive organs which help in reproduction.

Question 11.
In the figure given below, mark the ovule and pericarp.

Answer:

Question 12.
Why do gametes produced in large numbers in organisms exhibit external fertilisation?
Answer:
In external fertilisation, there are great chances that the sperm and the eggs released by the organisms can be affected by desiccation, predators, etc. So, to make up for the high fatality rate of the gametes, the organisms produces a lot of gametes.

Question 13.
Which of the followings are monoecious and dioecious organisms.
(a) Earthworm____________
(b) Chara ______________
(c) Marchantia____________
(d) Cockroach ___________
Answer:
(a) Earthworm – Monoecious animal
(b) Chara – Monoecious plant
(c) Marchantia- Dioecious plant
(d) Cockroach – Dioecious plant

Question 14.
Match the organisms given in Column ‘A’ with the vegetative propagules given in Column ‘B’

1. Rrunphyllum. – (c) Leaf buds
2. Agave –  (d)   Bulbils
3. Potato –  (b)   Eyes
4. Water hyacinth –  (a) Offset

Question 15.
What do the following parts of a flower develop into after fertilisation?
(a) Ovary__________
(b) Ovules__________
Answer:
(a) Ovary – fruit
(b) Ovules-seed

Short Answer Type Questions

Question 1.
In haploid organisms that undergo sexual reproduction, name the stage in the life cycle when meiosis Give reasons for your answer.
Answer:
In zygospore (formed by zygote) meiosis occurs. Because after meiosis it can form meiospores which can develop into haloid organisms.

Question 2.
The number of taxa exhibiting asexual reproduction is drastically reduced in higher plants (angiosperms) and higher animals (vertebrates) as compared with lower groups of plants and animals. Analyse the possible reasons for this situation.
Answer:
Both angiosperms and vertebrates have more complex structural organisation. They have evolved very efficient mechanism of sexual reproduction.

1. The offspring produced due to sexual reproduction adapt better to the changing environmental conditions.
2. Genetic recombination, interaction, etc. during sexual reproduction provide vigour and vitality to the offspring.

Question 3.
Honeybees produce their young ones only by sexual reproduction. Inspite of this, in a colony of bees we find both haploid and diploid  individuals Name the haploid and diploid individuals in the colony and analyse the reasons behind their formation.
Answer:
Honeybees produce their young ones by sexual reproduction but parthenogenesis also occurs alongwith sexual reproduction. Fertilised eggs and parthenogenetically developed eggs give rise to different castes. In honey bees, fertilised eggs (zygotes) which is diploid give rise to queens and workers (both are females) and unfertilised eggs (ova) which is haploid develop into drones (males).

Question 4.
With which type of reproduction do we associate the reduction division? Analyse the reasons for it.
Answer:
We can associate the reduction division (meiosis) with sexual reproduction. Sexual reproduction is the process of development of new organisms through the formation and fusion of male and female gametes. It involves meiosis or reduction division i.e., halving the parental chromosomes inside the male and female gamete and their subsequent fusion resulting in the restoration of the original parental number of chromosomes, causing an increased genetic diversity.

Question 5.
Is it possibletoconsider vegetative propagation observed in certain plants like Bryophyllum, water hyacinth, ginger etc., as a type of asexual reproduction? Give two/ three reasons.
Answer:
Yes, it is possible to consider vegetative propagation as a type of asexual reproduction because of the following reasons:

1. Production of plantlet occurs by a single parent plant without the formation and fusion of gametes.
2. Plantlets receives all genes from their one parent plant.
3. Vegetative reproduction involves only mitotic cell division.
4. There is no gamete formation.

Question 6.
Fertilisation is not an obligatory event for fruit production in certains plants’ Explain the statement.
Answer:
No, fertilisation is not an obligatory event for fruit production in certain plants, as fruits can also develop from unfertilised ovary also. Such fruits are called parthenocarpic  fruits. The formation of this type of fruit takes place without prior’fertilisation of the flower by pollen. The resulting fruits are seedless and therefore do not contribute to the reproduction of the plant, examples are bananas and pineapples. Plant growth substances may have a role in this phenomenon, which can be induced by auxins in the commercial production of tomatoes and other fruits.

Question 7.
In a developing embryo, analyse the consequences if cell divisions are not followed by cell differentiation.
Answer:
Cell division increase the number of cells in the developing embryo while cell differentiation helps the groups of cells to undergo certain modifications and form specialised tissues and organs.

Initially all the cells of the developing embryo are alike with same genetic information. Later however, due to the phenomenon of differentiation depending on their location and internal cellular mechanism, different cells of the embryo develop differently forming embryonal axis, plumule and radicle. However, if cell differentiation does not occur the embryo will remain just a mass of undifferentiated cells or callus. There would not any plumule, radicle, cotyledons or embryo axis. A new plant will not be formed from such an embryo.

Question 8.
List the changes observed in an angiosperm flower subsequent to pollination and fertilisation.
Answer:
In an angiosperm flower, the changes that occur subsequent to pollination and fertilisation are called post-fertilisation changes. Pollen grain germinates over the stigma and forms a pollen tube carrying two gametes. Pollen tube reaches ovary and enters an ovule through one of its synergids. Fertilisation produces a diploid zygote and triploid primary endosperm cell. Zygote produces embryo and primary endosperm cell forms endosperm. Transformation takes place and ovule transforms into seed, ovary transforms into fruit and ovary wall into pericarp. The petals, stamens and style wither away.

Question 9.
Suggest a possible explanation why the seeds in a pea pod are arranged in a row, whereas those in tomato are scattered in the juicy pulp.
Answer:
Arrangement of seeds inside a fruit depends upon the type of placentation and the growth of placental axis. In pea ovary, the ovules are attached to the ventral suture i.e., marginal placentation and carpel is mono- carpellary. So, seeds are arranged in a row. In tomatoes, the gynoecium is tricarpellary with axile placentation. The placentae grow and become pulpy during fruit formation. As a result seeds get scattered in the pulpy mass in tomato.

Question 10.
Draw the sketches of a zoospore and a conidium. Mention two dissimilarties between them and atleast one feature common to both structures.
Answer:

Dissimilarities : Zoospores are motile and flagellated whereas conidia are nonmotile. Zoospore are formed inside a zoosporangium and conidia are formed (exogenously) outside on a conidiophore.
Similarity : Both are reproductive structures for asexual reproduction.

Question 11.
Justify the statement’Vegetative reproduction is also a type of asexual reproduction’.
Answer:
Refer answer 5.

Long Answer Type Questions

Question 1.
Enumerate the differences between asexual and sexual reproduction. Describe the types of asexual reproduction exhibited by unicellular organisms.
Answer:

Asexual reproduction occurs usually in some organisms such as monerans, protists, in plants and in some animals.
Following are the methods of asexual reproduction in unicellular organisms :

(1) Binary fission : In this type of asexual reproduction, the parent organism divides into two halves, each half forms an independent daughter organism e.g.,

(2) Multiple fission : In this process, the parent body divides into many similar daughter individuals. Multiple fission occurs in Amoeba during unfavourable condition.

(3) Bidding : In budding, a daughter individual is formed from a small part or bud, arising from the parent body g., yeast.
Spore formation or sporulation : Spores are minute, single celled, thin or thick walled propagules. In this type of asexual reproduction dispersive structures called spores are released from parent body that germinate under favourable conditions to form new individuals. Motile spores called zoospores are formed in unicellular alga like

Question 2.
Do all the gametes formed from a parent organism have the same genetic composition (identical DNA copies of the parental genome)? Analyse the situation with the background of gametogenesis and provide or give suitable explanation.
Answer:
No, All the gametes formed from a parent organism don’t have the same genetic combination. Formation of two types of gametes-male and female, inside the gametangia, is called gametogenesis. The reproductive units in sexual reproduction are specialised cells called gametes. The gametes are generally of two kinds : male and female. The gametes of all the organisms are usually haploid cells, i.e., possess single set (or n number) of chromosomes. The gametes are usually formed by meiotic divisions. Therefore, they are haploid, i.e., have halved or reduced (n) number of chromosomes. During this processes, random segregation of chromosomes (independent assortment) and exchange of genetic material between homologous chromosomes (crossing over) result in new combinations of genes in the gametes, and this reshuffling increases genetic diversity. The coming together of two unique sets of chromosomes in the zygote forms the genetic basis of variation within the species.

Question 3.
Although sexual reproduction is a long drawn, energy-intensive complex form of reproduction, many groups of organisms in Kingdom Animalia and Plantae prefer this mode of reproduction. Give atleast three reasons for this.
Answer:
Reasons for preference of sexual reproduction in higher groups of organisms are as follows:

1. During sexual reproduction, there is fusion of gametes, hence genetic recombination takes place causing variations.
2. The offspring produced due to sexual reproduction adapt better to the changing environmental conditions.
3. Genetic recombination, interaction, etc. during sexual reproduction provide vigour and vitality to the offspring.
4. Variation being a major factor of natural selection, therefore, it plays an important role in evolution.

Question 4.
Differentiate between
(a) oestrous and menstrual cycles;
(b) ovipary and vivipary. Cite an example for each type.
Answer:
(a) Differences between menstrual and oestrous cycles are as follows:

 (b) Differences between ovipary and vivipary are as follows:

Question 5.
Rose plants produce large, attractive bisexual flowers but they seldom produce fruits. On the other hand a tomato plant produces plenty of fruits though they have small flowers. Analyse the reasons for failure of fruit formation in rose.
Answer:
Both rose and tomato plants are selected by human beings for different characteristics, the rose for its flower and tomato for its fruit. Rose plant is vegetatively propagated and does not produce seeds. Fruit formation fails in rose plant due to following reasons:

1. Viable pollen may not be produced, resulting in failure of fertilisation.
2. Functional egg may not be produced.
3. The ovule produced may be defective or non functional.
4. There may be pollen-pistil incom­patibility.
5. The plant may be a hybrid with abnormal segregation of chromosomes resulting in non-viable gametes.
6. The plant may be a hybrid and sterile.
7. There may be internal barriers for growth of pollen tube and fertilisation

We hope the NCERT Exemplar Solutions for Class 12 Biology chapter 1 Reproduction in Organisms help you. If you have any query regarding NCERT Exemplar Solutions for Class 12 Biology chapter 1 Reproduction in Organisms, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 10 Social Science Economics Chapter 2 Sectors of Indian Economy

These Solutions are part of NCERT Solutions for Class 10 Social Science. Here we have given NCERT Solutions for Class 10 Social Science Economics Chapter 2 Sectors of Indian Economy.

TEXTBOOK EXERCISES

Question 1.
Fill in the blanks using the correct option given in the brackets :

1. Employment in the service sector__________ increased to the same extent as production. (has/has not)
2. Workers in the__________ sector do not produce goods. (tertiary/agricultural)
3. Most of the workers in the___________ sector enjoy job security. (organised/unorganised)
4. A_______ proportion of labourers in India are working in the unorganised sector.  (large/small)
5. Cotton is a__________ product and cloth is a____________ (natural/manufactured)
6. The activities in primary, secondary and tertiary sectors are______________ (independent/interdependent)

Answer:

1. has not
2. tertiary
3. organised
4. large
5. natural; manufactured
6. interdependent

Question 2.

1. How the sectors are classified on the basis of ownership of enterprises?
2. What is the secondary sector?
3.  What is GDP?
4. In terms of GDP what was the share of the tertiary sector in 2003?

Answer:

1. Public and Private sector.
2. Production of a commodity, mostly through the natural process is called the secondary sector.
3. GDP is the sum total of the value of all final goods and services of three sectors.
4. Between 50 percent to 60 percent.

Question 3.

1. How the problem of unirrigated land can be solved?
2. How the problem of low prices for crops can be solved? Give one solution.
3. How the debt burden of the farmers can be reduced?
4. How people/farmers can be provided a job in the offseason?
5. “The farmers are compelled to sell their grains to the local traders soon after harvest.” How this can be avoided?

Answer:

1. The problem of unirrigated land can be solved by the construction of canals by the government.
2. This problem can be solved by setting up cooperative marketing societies.
3. The debt burden of the farmers can be reduced by banks by granting credit at low interest.
4. The farmers can be given jobs in the offseason by setting up agro-based mills.
5. This can be avoided by the procurement of foodgrains by the government at a reasonable/ fixed price.

Question 4.
Classify the following workers under their correct sector :
Tourist guide, vegetable vendor, cobbler, Sahara Airlines
Answer:

1. Tourist guide – Organised sector
2. Vegetable vendor – Unorganised sector
3. Cobbler – Service sector
4. Sahara Airlines – Private sector

Question 5.
A research scholar looked at the working people in the city of Surat and found the following :

Complete the table. What is the percentage of workers in the unorganized sector in this
city (in percent) ?                                                                                            ,
Answer:
Complete table is given below :

Question 6.
Do you think the classification of economic activities into primary, second­ary, and tertiary sectors is useful? Explain how.
Answer:
The classification of economic activities into primary, tertiary and secondary is useful on account of the information it provides on how and where the people of a country are employed. also this helps in ascertaining as to which sector of economic activity contributes more or less to the country’s GDP and per capita income.

If the tertiary sector is developing much faster than the primary sector, then it implies that agriculture is depleting, and the government must take measures to rectify this. The knowledge that the agricultural profession is becoming unpopular or regressive can only come if we know which sector it belongs to. Hence it is necessary to classify economic activities into these there sectors for smooth economic administration and development.

Question 7.
For each of the sectors that we came across in this chapter, why should one focus on employment and GDP? Could there be other issues that should be examined? Discuss.
Answer:
For each of the sectors mentioned in this chapter, our focus should definitely be on employment and GDP. This is because growth in GDP and full employment are common goals of Five Year Plans and they also determine the size of a country’s economy. A focus on employment and GDP helps us to calculate and monitor the most important factors like per capita income, productivity, changes in employment rate, and contribution to GDP by the three sectors of the economy and thus, takes necessary steps required for the upliftment of the country’s economy as a whole.
Yes, the other issues which should be examined are

1. balanced regional development
2. equality in income and wealth among the people of the country.
3. how to eradicate poverty
4. modernization of technology
5. self-reliance of the country
6. how to achieve surplus food production in the country.

Question 8.
Make a long list of all kinds of work that you find adults around you doing for a living. In what way can you classify them? Explain your choice.
Answer:
(1) List of working adults: Engineer, doctor, washerman, electrician, shopkeeper, milk vendor, insurance manager, professor, government employee, a zamindar, vegetable seller, domestic help, a factory owner.

(2) Classification of the above kinds of work :

• Primary sector: Zamindar (landowner).
• Secondary sector: Factory owner.
• Tertiary sector: Engineer, doctor, washerman, electrician, shopkeeper, milk vendor, insurance manager, professor, government employee, vegetable vendor, and domestic help.
• Organised sector: Engineer, insurance manager, and doctor.
• Unorganised sector: Washerman, vegetable vendor, milk vendor, shopkeeper, electri­cian and domestic help.
• Public sector: Government employee and professor in a government college.
• Private sector: Engineer and doctor.

Question 9.
How is the tertiary sector different from other sectors? Illustrate with a few examples.
Answer:
The tertiary sector different from other two sectors. This is because other two sectors produce goods but, this sector does not produce goods by itself. But the activities under this sector help in the development of the primary and secondary sectors. These activities are an aid or support for the production process. For example, transport, communication, storage, banking, insurance, trade activities etc. For this reason this sector is also known as service sector.

Question 10.
What do you understand by disguised unemployment? Explain with an example each from the urban and rural areas.
Answer:
(1)

1. Disguised unemployment is a situation in which more people are engaged in an activity than the required ones,
2. This kind of Buder-employment is hidden in contrast to someone who does not have a job and is clearly visible as unemployed.
3. Hence it is also called disguised unemployment,
4. Under disguised unemployment even if the surplus people are removed from work, the production does not suffer.

(2) Rural areas: In rural area in India, more people are employed in agriculture than necessary. Even if you move a few people out, production will not be affected. As such workers in the agricultural sector are underemployed.

(3) Urban areas:

1. The disguised unemployment or under-employment exists in urban areas too. For example, there are thousands of casual workers in the service sector who search for daily employment,
2. They are employed as painters, plumbers and repairpersons and other doing odd jobs,
3. Many of them do not find work every day,
4. Similarly, there are other people of the service sector on the street pushing a cart or selling something who may spend the whole day but earn very little. They do this work because they do not have better opportunities.

Question 11.
Distinguish between open unemployment and disguised unemployment.
Answer:
The differences between open unemployment and disguised unemployment are as mentioned below :

Question 12.
“The tertiary sector is not playing any significant role in the development of Indian economy.” Do you agree? Give reasons in support of your answer.
Answer:
No, I do not agree with the statement that tertiary sector is not playing any significant role in the development of Indian economy. The reasons are as follows:

1. In terms of GDP this sector emerged as the largest producing sector in India surpassing the primary and secondary sectors. In 1973, the share of the tertiary sector in GDP was about 35% which increased to more than 50% in 2003. Over the thirty years between 1973 and 2003, while production in all three sectors increased, it has been the most in tertiary sector.

2. In terms of employment also the rate of growth of employment in tertiary sector between the same period was nearly 250%. This was negligible in primary sector.

Question 13.
Service sector in India employs two different kinds of people. Who are these ?
Answer:
Service sector in India employs two different kinds of people as mentioned below :

1. There are highly skilled and educated workers such as teachers and doctors.
2. On the other hand, a large number of workers are engaged in services such as small shopkeepers, repair persons etc. who barely manage to earn a living. They perform these services because they do not have any other work to do.

Question 14.
Workers are exploited in the unorganised sector. Do you agree with this view ? Give reasons in support of your answer.
Answer:
It is a fact that the workers are exploited in the unorganised sector due to the following reasons :

1. The unorganised sector consists of small and scattered units which are largely outside the control of the government.
2. There are rules and regulations but generally these are not followed by the employers.
3. Workers are employed on irregular basis. They are low paid and there is no provision
   for overtime, paid leave, holidays, leave due to sickness and other facilities e.g., provident fund.
4. Jobs are not secured. They can be asked to leave without any reason at the sweet will of the employer. Generally, when there is less work due to any reason, some workers are asked to leave.
5. Workers in this sector face social discrimination too because most of them belong to Scheduled Castes, Scheduled Tribes and Other Backward Classes.
6. Some workers who do repair work etc. are also exploited as they do not get regular work.
7. Farmers work on their own and hire labourers as and when they require.

Question 15.
How are the activities in the economy classified on the basis of employment conditions?
Answer:
Organised sector and unorganised sector.

Question 16.
Compare the employment conditions prevailing in the organised and unor­ganised sectors.
Answer:
The conditions in the organised and unorganised sectors are as follows :

Question 17.
Explain the objective of implementing the NREGA 2005.
Answer:
The objective of implementing the NREGA 2005 was to provide 100 days of guaranteed employment to those people in rural India who can work, and are in need of work. This Right to Work has been implemented in 200 districts. If the government is unable to provide this employment, then it has to give unemployment allowances to the people.

Question 18.
Using examples from your area compere and contrast the activities and functions of private and public sectors?
Answer:
The activities and functions of private and public sectors in our area may be compared as mentioned below :

Question 19.
Discuss and fill the following table giving one example each from your area :

Answer:

 In the public sector, the services provided by MTNL are better than others and are cheap too. On the other hand, the services provided by the MCD such as sanitation are not satisfactory. Sometimes, the sewers are blocked during rainy season creating health problems in the area.

In the private sector, there are a few private nursing homes and hospitals which provide good medical facilities. But some of the companies such as TPDDL in the private sector have not risen up to the mark. There are still ‘breaks’ in the supply of electricity in the area which cause hardship to the people.

Question 20.
Give a few examples of public sector activities and explain why the govern­ment has taken them up.
Answer:
(1) A few examples of public sector activities are as mentioned below :

• Electricity – production and distribution.
• Selling of food grains – wheat and rice.
• Health and education.
• Safe drinking water.
• Housing facilities for the poor.
• To take care of the poorest and ignored regions.

(2) The government takes up the public sector activities due to the following reasons:

• The modern state is a welfare state which looks after the interests of the people. The government raises money through taxes and other ways and spends on public sector activities for the welfare of the people.
• Selling electricity at the cost of generation may push up the costs of production of industries. Small scale units may shutdown. Therefore government steps in by producing and supplying electricity at rates which these industries can afford. Govt, has to bear part of the cost.
• To have food security in the country, the government of India buys wheat and rice from farmers at a ‘fair price’. These are stored in its godowns and sold at a lower price to consumers through ration shops. The government bears some cost and in this way it supports both farmers and consumers.
• In modern welfare state, it is the responsibility of the government to provide health and education facilities for all citizens. Running proper schools and providing quality education is the duty of the government.
• In India half of children are malnourished. Hence government pays attention to aspects of human development such as availability of safe drinking water, housing facilities for the poor and food and nutrition.
• It is also the duty of the govt, to take care of the poorest and most ignored regions of the country through increased spending in such areas.

Question 21.
Explain, how public sector contributes to the economic development of a nation.
Answer:
Generally, economic development of a nation can be defined as long term increase in per capita income alongwith improvement in quality of life. The public sector contributes to the economic development of a nation in many ways as mentioned below :

• In public sector, the government owns most of the assets and provides services to the people. For example Railways and Post Offices. Railways is the biggest public undertaking. It is very useful for people, traders and industrialists. It is the most dependable mode of transport as it is least affected by weather conditions such as rain, fog compared to other modes of transport. It is better organised than any other form of transport. It is suitable for bulky and heavy goods.
  It is cheaper transport. It is the largest public undertaking. The railways provide greater employment opportunities for both skilled and unskilled labour. Over 16 lakh persons are depending upon railways for their livelihood. Thus it contributes a lot towards the economic development of the country.
• Public sector helps in development through Creation and infrastructure.
• It helps in the development of small, medium and cottage industries.
• It contributes to community development i.e., to the Human Development Index via health and educational facilities.
• It tries to ensure equality of income wealth and thus a balanced regional development.
• It ensures easy availability of goods at moderate rates.
  In India, the public sector has played a significant role in the eradication of illiteracy. The number of literates has increased from 9 per cent of females and 27 per cent of males in 1951 to 75 per cent of males and 54 per cent females in 2001. The government’s efforts in providing health facilities has raised average life expectancy from 32 years in 1950-51 to 61 years in 1993­Thus, we find that public sector contributes to the economic development of a nation in a significant way.

Question 22.
The workers in the unorganised sector need protection on the following issues : wages, safety and health. Explain with examples.
Answer:
(1) Wages: The workers in the unorganised sector do not get minimum wage fixed by the government. They are not paid any allowances like dearness allowance or city compensatory allowance. They are paid only their wages. They are not paid for the extra time, they work in the factory. They do not get any leave or paid holiday.

(2) Safety: No safety measures are taken in the factories for the protection of the workers. This results in injuries or death of labourers in the factory in case of fire or any other accident.

(3) Health: The workers in the unorganised sector are not provided any medical facilities. Whenever they fall ill or get injured, they get themselves treated by private doctors by paying for the treatment. Sometimes the working conditions are not hygienic. They are not paid any medical allowance too. Lack of medical facilities affect their health and efficiency badly.

Question 23.
A study in Ahmedabad found that out of 15,00,000 workers in the city, 11,00,000 worked in the unorganised sector. The total income of the city in this year (1997-98) was ? 60,000 million. Out of this ? 32,000 million was generated in the organised sector. Present this data as a table. What kind of ways should be thought of for generating more employment in the city ?
Answer:
(1) The data is given below as a table :

(2) The following ways or steps should be taken by the government for generating more employment in the city :

1. Electricity should be provided to the factories regularly and at cheap rate especially to the small units. Government should bear part of the cost.
2. Adequate land should be given to people to’set up factories or small units.
3. Financial assistance should be given at less rate of interest.
4.  Raw materials should be made available to the factory owners and other small unit holders.
5. Transport and other facilities should be made’available.

Question 24.
The following table gives you the GDP in Rupees (crore) by the three sectors :

(1) Calculate the share of the three sectors in GDP for 1950 and 2000.
(2) Show the data as a bar diagram similar to Graph 2 in the chapter.
(3) What conclusions can we draw from the bar graph
Answer:
(1) The share of the three sectors in GDP for 1950 and 2000 was as given below :

(2) Share of sectors in GDP is shown in the bar diagram given below :

(3) From the bar diagram the following conclusions can be drawn :

In 1950, the share of primary sector in GDP was more than other sectors. It was 57.97% in comparison to 13.77% and 28.26% of secondary and tertiary sectors respectively.
However in 2000, the share of primary sector decreased from 57.97% to 27.32% while the share of tertiary sector increased from 28.26% to 48.32%. The share of secondary sector too increased from 13.77% in 1950 to 24.36% in 2000

We hope the NCERT Solutions for Class 10 Social Science Economics Chapter 2 Sectors of Indian Economy help you. If you have any query regarding NCERT Solutions for Class 10 Social Science Economics Chapter 2 Sectors of Indian Economy, drop a comment below and we will get back to you at the earliest.