NIOS Class 12 Biology Chapter 21 Reproduction and Population Control

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NIOS Class 12 Biology Chapter 21 Reproduction and Population Control

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Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Biology Chapter 21 Reproduction and Population Control Solutions, NIOS Senior Secondary Course Biology Solutions for All Chapter, You can practice these here.

Reproduction and Population Control

Chapter: 21

MODULE – III: REPRODUCTION AND HEREDITY

NIOS TEXTBOOK QUESTIONS ANSWERS

INTEXT QUESTIONS 21.1

1. At what age do human males and females attain puberty?

Ans: (a) Male: 13-14 years of age.

(b) Female: 11 to 13 years of age.

2. Name the tubules present in the human testis.

Ans: Seminiferous tubules.

3. Name the various parts of the following:

(i) Human male reproductive system. 

Ans: Testis, epididymis, vas deferens, urethra and penis. 

(ii) Human female reproductive system.

Ans: Ovaries, fallopian tubes, uterus and vagina.

4. Name the three types of accessory glands found in the human male reproductive system.

Ans: (i) Seminal vesicles.

(ii) Prostate glands. and 

(iii) Cowper’s glands.

5. State the functions of the following:

(a) Seminal vesicles.

Ans: Stocks sperms and provide them nourishment. 

(b) Prostate glands.

Ans: It secretes an alcaline fluid, thin fluid that keeps sperms alive. It helps them to swim vigorously.

(c) Uterus.

Ans: It secretes a white viscous, alkaline secretion which acts as a lubricant.

Inner lining receives, protects and nourishes embryo; contraction of muscular wall exits baby during birth.

6. What is a gemmule? Explain its importance in the life of sponges.

Ans: Gemmule: It is an asexual reproductive body in sponges like spongilla. It is helpful to overcome drought period and make new gemmules from archaeocytes under favourable times.

7. State the functions of the following in insects:

(a) seminal vesicles in male.

Ans: Store sperms.

(b) spermatheca in female.

Ans: Receive sperms.

(c) testes in males.

Ans: Generate sperms

(d) ovaries in females.

Ans: Ovaries produce eggs in females. 

INTEXT QUESTIONS 21.2

1. State the main function of placenta. 

Ans: It supplies O₂ and food from maternal blood to the foetus and transports CO₂ and wastes from body of foetus to maternal blood.

2. Define the following terms: 

(i) Implantation.

Ans. The fixation of morula in the wall of uterus is knows as implantation.

(ii) Placenta.

Ans: It is the association between maternal and foetal tissue for physiological exchange, developing embryo is attached to the uterus by tissue.

(iii) Morula.

Ans: Morula: Zygote starts to divide. It forms mass cells termed as morula.

(iv) Amnion.

Ans: Amnion: From the first few stages of embryonic development, embryo is enclosed in a sac named the amnion.

3. Name the fluid surrounding the uterus.

Ans: Amniotic fluid.

4. Write the function of:

(a) Prolactin.

Ans: Responsible for stimulation of mammary glands to secrete milk.

(b) Oxytocin.

Ans: Responsible for child birth.

5. The first milk that comes out of the mammary gland of the mother is called __________ Why is this first milk important for the child?

Ans: Colostrum: It provides immunity to child. 

INTEXT QUESTIONS 21.3

1. List any four reasons for population explosion in India.

Ans: (i) Illiteracy.

(ii) Desire for son.

(iii) Religious and social custom.

(iv) Advancement in agriculture.

2. What is the inter-relationship between population, environment and development?

Ans: Environmental degradation is caused by overpopulation that affects the environment and development.

3. What is the effect of uncontrolled population growth on us and our nation? 

Ans: (i) Environmental degradation.

(ii) Urbanisation. 

(iii) Depleting energy sources. 

4. How does population growth influence urbanisation and environmental degradation?

Ans: The people move to cities to find jobs. The growth in urban areas cause pollution, slums, etc.

5. Relate the indiscriminate increase in population with the standard of living in our country.

Ans: With increase in population, there is degradation of environment. Overcrowding causes depletion of fuel, food, resources, etc.

TERMINAL EXERCISES

1. Define the following terms.

(i) Demography.

Ans: Demography: It is the study of human population.

(ii) Vasectomy.

Ans: Vasectomy: It is a method of sterilisation in males when vas deferens are cut and tied.

(iii) IUD.

Ans: IUD: Intrauterine Device: Copper T is introduced in female’s reproductive tract to prevent implantation.

2. Mention if the following statements are True (T) or False (F) and rewrite the wrong statements in the correct form. 

(i) Fertilisation occurs in vagina.

Ans: False: Fertilisation occurs in fallopian tube.

(ii) Oxygen and nutrients diffuse from mother’s blood into foetus’s blood through amnion.

Ans: False: Oxygen and nutrients diffuse from mothers blood into foetus blood through placenta.

(iii) Testes produce testosterone hormone.

Ans: True.

(iv) Pregnancy in women can be prevented by the method of vasectomy.

Ans: True.

(v) Tubectomy involves the cutting and tying of the vas deferens in male.

Ans: False: Tubectomy involves the cutting and tying of fallopian tubes in females.

3. Choose the odd one in each of the following: 

(i) Ovary; Fallopian tube; ureter; uterus; 

Ans: ureter.

(ii) Epididymis; urethra; vas deferens; uterus.

Ans: uterus.

(iii) Graafian follicle; corpus luteum; Leydig cell.

Ans: Leydig cell.

(iv) Amnion; corpus luteum; amniotic fluid; umbilical cord.

Ans: umbilical cord.

4. Match the terms of Column-I with those of Column-II and write down the matching pairs.

Ans:

5. What is reproduction? List the organs of the human male reproductive system.

Ans: Reproduction: It refers “to the ability of living organisms by which they produce offspring of their own kind”.

Human Male Reproductive System: The male reproductive organs consists of the following:

(i) A part of testis.

(ii) Epididymis.

(iii) Seminal vesicle.

(iv) Prostate gland.

(v) Urethra.

Testes: There are a pair of oval testis. Each is enclosed in scrotal sacs. In the testes sperms are produced.

Epididymis: It is a tubelike structure which is firmly attached to the testis and is connected with the seminiferous tubules. It is the main store house of the sperm.

Seminal Vesicles: These are a pair of thin called muscular elongated lobulated sacs. They lie at the base of the urinary bladder above the prostate gland. They unite to form ejacu-latory duct.

Fig. 21.2. Male Reproductive Organs.

The duct system: It involves vasa efferentia, vas deferens, epididymis and urethra.

(a) Vasa efferentia: Very fine ducts are attached to each testis. Sperms are passed by these ducts into the epididymis.

(b) Epididymis: It is a convoluted and elongated tube. It is fitted over the tip of the testis as a cap. It goes upto urethra and vas deferens. Epididymis stores the sperms.

(c) Vasa defferentia: These are sperm ducts. Vas deferens from each testis passes over the urinary bladder in the abdominal region. It unites to the duct of seminal vesicle and forms ejaculatory duct which passes through prostate gland. These ducts conducts spermatozoa.

(d) Urethra: The vasa deferentia (both) unite to form urethra. It continues through the penis and opens outside by urogenital opening. It serves to carry sperms and urine both.

Penis External genital organ of male human is penis. It consists of spongy muscle tissue. Its tip is enclosed by glans penis. Glans penis is covered by prepuce. Penis releases semen during copulation.

Glands: Seminal vesicles, prostate gland, Cowper’s gland and urethral glands are associated to the male genital system.

6. What is placenta? How is the placenta beneficial to the mother and the foetus?

Ans: Placenta is a “device which connects the embryo with the uterine wall of mother in higher mammals”.

The Physiology of Placenta: Placenta allows exchange of substances between embryo and mother. Its various functions are:

1. It transports amino acids, lipids, glucose, vitamins, water, minerals and hormones from mother of foetus.

2. Oxygen is diffused from maternal blood into foetus and CO₂ from foetus passes into the maternal though placenta.

3. Nitrogeneous wastes like urea and uric acid escape through the placenta into maternal system.

4. Only useful substances are passed into the foetus through placenta and it also prevents harmful ones like bacteria from passing through it.

5. Placenta stores fat, glycogen and iron for embryo before formation of liver.

6. Placenta sectrete certain hormones which help in maintaining pregnancy and prevent premature birth. Relaxin scereted by placenta helps in birth by stimulating contraction of muscles of uterus.

7. What is the significance of testes being located in scrotal sac outside the abdomen of human males?

Ans: The testes lie in scrotum outside the abdomen of human males as it acts as thermoregulator. It helps to maintain the temperature of testes at opp. 2-3°C lower than temperature of body. This temperature is suitable for development of the sperms.

8. Write in a sequence the region through which sperm travels from seminiferous tubules up to the urethral opening in human males.

Ans: Seminiferous Tubule of Testis → Epididymis → Vas deferens→ Seminal vesicles → Ejaculatory duct → Eurethra → Penis.

9. How can the knowledge of process of reproduction help in reducing population growth? Give reasons.

Ans: The knowledge of reproduction and reproductive health decrease population growth. India has started action plans under RCH programmes. Family planning measures are adopted by couples.

10. How does increasing population affect environment?

Ans: The increasing population has many environmental implication such as crowding, depletion of food, land, fuel, consumer resources and the reduction in per capita income. It leads to degration of environment. Increase in automobiles lead to pollution.

11. Name the following:

(i) The organ in which the foetus develops in a human female.

Ans. Uterus.

(ii) The male gamete in humans.

Ans. Sperm.

(iii) The fluid surrounding the developing embryo.

Ans: Amniotic fluid.

(iv) Stage when menstruation and ovulation stops in females.

Ans: Menopause.

(v) The surgical method of contraception in human female.

Ans: Sterilisation (Vasectomy and tubectomy).

12. Differentiate between the following:

(i) Implantation and pregnancy.

Ans. Difference between Implantation and Pregnancy:

(ii) Graafian follicle and corpus luteum.

Ans. Difference between Graafian follicle and Corpus luteum:

(iii) Identical twins and fraternal twins.

Ans. Difference between Identical Twins and Fraternal Twins:

(iv) Birth rate and death rate.

Ans. Difference between Death-rate and Birth-rate:

(v) Vasectomy and tubectomy.

Ans. Differences between tubectomy and Vasectomy:

13. Draw the outline of the cross section of the male reproductive system.

(i) Label the following parts.

(a) testis. 

(b) epididymis.

(c) seminal Vesicles.

(d) vas deferens.

Ans: See the figure:

Fig. 21.3. Human male reproductive organs.

(ii) Name the hormone produced by the testis.

Ans: Testis produce testerone, male sex hormone (androgen).

(iii) Why are sperms produced in large numbers?

Ans: The sperms are produced in large numbers because they have to reach to the egg (ovum) for fertilisation. Some of then fail to reach their destination.

(iv) State the function of the seminal vesicles.

Ans: Function of Seminal Vesicles: They join to form ejaculatory duct. They store sperms.

14. Write a note on: 

(i) Lactation in humans.

Ans. Lactation: The milk is secreted from mammary glands of female human/woman during lactation period. First few drop of this milk are called colostrum just after child birth. Lactation is stimulated by prolactin hormone produced by pituitary gland.

(ii) Gemmule.

Ans. Gemmule: It is a reproductive body in sponges (Porifera) for asexual reproduction e.g. water and marine sponges.

Gemmule, a minute hard ball like structure having archaeocytes enclosed by a covering. Microphyle is opening from it; from where archaeocytes come out to form a sponge.

(iii) Cockroach ovaries.

Ans. Cockroach ovaries: There are 2 pairs of ovaries which lie on either side of hind gut; embedded in fat bodies.