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Biology · Class 12 Science

Ch 2Human Reproduction — Class 12 Biology, concept-first.

Humans reproduce sexually, and are viviparous — giving birth to live young rather than laying eggs. The full sequence runs: gametogenesis (forming sperm in males, ova in females), insemination (sperm delivered into the female reproductive tract), fertilisation (sperm and egg fusing into a zygote), implantation (the res…

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Key concepts

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Human Reproduction

Think about what makes you you. You have your mother's eyes, your father's laugh, a mix of traits from two people you may never have met — your grandparents.

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Chapter contents

The NCERT structure, section by section. Open a section to see its questions, then read the concept-first solution.

Introduction

Humans reproduce sexually, and are viviparous — giving birth to live young rather than laying eggs. The full sequence runs: gametogenesis (forming sperm in males, ova in females), insemination (sperm…

2.1

The Male Reproductive System

The male reproductive system is located in the pelvis region. It is a system built for the production, storage, and transport of sperm, as well as the delivery of these gametes into the female reprodu…

2.2

The Female Reproductive System

The female reproductive system is designed to carry out several functions: produce the female gamete (the ovum), receive the male gamete (the sperm), provide a suitable environment for fertilisation a…

2.3

Gametogenesis

Reproduction in humans requires the formation of specialised sex cells — the male gamete (sperm) and the female gamete (ovum).

2.4

Menstrual Cycle

The menstrual cycle is the rhythmic, monthly series of changes that occur in the female reproductive system, preparing the body for a possible pregnancy.

2.5

Fertilisation and Implantation

Fertilisation is the fusion of a sperm with an ovum to form a single-celled zygote. In humans, this event takes place in the ampullary region of the fallopian tube, close to the isthmus.

2.6

Pregnancy and Embryonic Development

The journey from fertilisation to the birth of a fully formed baby is called pregnancy, and the process by which the baby grows inside the mother is embryonic development.

2.7

Parturition and Lactation

The journey from fertilisation to birth is a carefully orchestrated sequence of events. After the embryo implants in the uterus, it develops over approximately nine months into a fully formed foetus.

Summary

- Male reproductive system: Testes (in scrotum, 2-3 degrees Celsius cooler) house seminiferous tubules for spermatogenesis; Leydig cells secrete testosterone; Sertoli cells nourish sperm.

Exercises

+Show 21 questions21 questions
  1. 2.1Fill in the blanks: (a) Humans reproduce _____________ (asexually/sexually) (b) Humans are _____________ (oviparous, viviparous, ovoviviparo…Free
  2. 2.2Draw a labelled diagram of male reproductive system.Free
  3. 2.3Draw a labelled diagram of female reproductive system.Free
  4. 2.4Write two major functions each of testis and ovary.Preview
  5. 2.5Describe the structure of a seminiferous tubule.Preview
  6. 2.6What is spermatogenesis? Briefly describe the process of spermatogenesis.Preview
  7. 2.7Name the hormones involved in regulation of spermatogenesis.Preview
  8. 2.8Define spermiogenesis and spermiation.Preview
  9. 2.9Draw a labelled diagram of sperm.Preview
  10. 2.10What are the major components of seminal plasma?Preview
  11. 2.11What are the major functions of male accessory ducts and glands?Preview
  12. 2.12What is oogenesis? Give a brief account of oogenesis.Preview
  13. 2.13Draw a labelled diagram of a section through ovary.Preview
  14. 2.14Draw a labelled diagram of a Graafian follicle.Preview
  15. 2.15Name the functions of the following: (a) Corpus luteum (b) Endometrium (c) Acrosome (d) Sperm tail (e) FimbriaePreview
  16. 2.16Identify True/False statements. Correct each false statement to make it true. (a) Androgens are produced by Sertoli cells. (True/False) (b)…Preview
  17. 2.17What is menstrual cycle? Which hormones regulate menstrual cycle?Preview
  18. 2.18What is parturition? Which hormones are involved in induction of parturition?Preview
  19. 2.19In our society the women are often blamed for giving birth to daughters. Can you explain why this is not correct?Preview
  20. 2.20How many eggs are released by a human ovary in a month? How many eggs do you think would have been released if the mother gave birth to iden…Preview
  21. 2.21How many eggs do you think were released by the ovary of a female dog which gave birth to 6 puppies?Preview

Exemplar Problems

Higher-order thinking / exemplar-style practice problems.

+Show 48 questions48 questions
  1. Q1Choose the incorrect statement from the following: (a) In birds and mammals internal fertilisation takes place (b) Colostrum contains antibo…Free
  2. Q2Identify the correct statement from the following: (a) High levels of estrogen triggers the ovulatory surge. (b) Oogonial cells start to pro…Free
  3. Q3Spot the odd one out from the following structures with reference to the male reproductive system: (a) Rete testis (b) Epididymis (c) Vasa e…Free
  4. Q4Seminal plasma, the fluid part of semen, is contributed by: (i) Seminal vesicle (ii) Prostate gland (iii) Urethra (iv) Bulbourethral gland (…Preview
  5. Q5Spermiation is the process of the release of sperms from: (a) Seminiferous tubules (b) Vas deferens (c) Epididymis (d) Prostate glandPreview
  6. Q6Mature Graafian follicle is generally present in the ovary of a healthy human female around: (a) 5 – 8 day of menstrual cycle (b) 11 – 17 da…Preview
  7. Q7Acrosomal reaction of the sperm occurs due to: (a) Its contact with zona pellucida of the ova (b) Reactions within the uterine environment o…Preview
  8. Q8Which one of the following is not a male accessory gland? (a) Seminal vesicle (b) Ampulla (c) Prostate (d) Bulbourethral glandPreview
  9. Q9The spermatogonia undergo division to produce sperms by the process of spermatogenesis. Choose the correct one with reference to above. (a)…Preview
  10. Q10Match between the following representing parts of the sperm and their functions and choose the correct option. Column I: A. Head, B. Middle…Preview
  11. Q11Which among the following has 23 chromosomes? (a) Spermatogonia (b) Zygote (c) Secondary oocyte (d) OogoniaPreview
  12. Q12Match the following and choose the correct options. Column I: A. Trophoblast, B. Cleavage, C. Inner cell mass, D. Implantation. Column II: i…Preview
  13. Q13Which of the following hormones is not secreted by human placenta? (a) hCG (b) Estrogens (c) Progesterone (d) LHPreview
  14. Q14The vas deferens receives duct from the seminal vesicle and opens into urethra as: (a) Epididymis (b) Ejaculatory duct (c) Efferent ductule…Preview
  15. Q15Urethral meatus refers to the: (a) Urinogenital duct (b) Opening of vas deferens into urethra (c) External opening of the urinogenital duct…Preview
  16. Q16Morula is a developmental stage: (a) Between the zygote and blastocyst (b) Between the blastocyst and gastrula (c) After the implantation (d…Preview
  17. Q17The membranous cover of the ovum at ovulation is: (a) Corona radiata (b) Zona radiata (c) Zona pellucida (d) ChorionPreview
  18. Q18Identify the odd one from the following: (a) Labia minora (b) Fimbriae (c) Infundibulum (d) IsthmusPreview
  19. Q19Given below are the events in human reproduction. Write them in correct sequential order. Insemination, gametogenesis, fertilisation, partur…Preview
  20. Q20The path of sperm transport is given below. Provide the missing steps in blank boxes.Preview
  21. Q21What is the role of cervix in the human female reproductive system?Preview
  22. Q22Why are menstrual cycles absent during pregnancy?Preview
  23. Q23A two-column table pairs certain organs of the human female reproductive system (Column A) with an associated event or function (Column B).…Preview
  24. Q24From where the parturition signals arise-mother or foetus? Mention the main hormone involved in parturition.Preview
  25. Q25What is the significance of epididymis in male fertility?Preview
  26. Q26Give the names and functions of the hormones involved in the process of spermatogenesis. Write the names of the endocrine glands from where…Preview
  27. Q27The mother germ cells are transformed into a mature follicle through series of steps. Provide the missing steps in the blank boxes.Preview
  28. Q28During reproduction, the chromosome number (2n) reduces to half (n) in the gametes and again the original number (2n) is restored in the off…Preview
  29. Q29What is the difference between a primary oocyte and a secondary oocyte?Preview
  30. Q30What is the significance of ampullary–isthmic junction in the female reproductive tract?Preview
  31. Q31How does zona pellucida of ovum help in preventing polyspermy?Preview
  32. Q32Mention the importance of LH surge during menstrual cycle.Preview
  33. Q33Which type of cell division forms spermatids from the secondary spermatocytes?Preview
  34. Q34A human female experiences two major changes, menarche and menopause during her life. Mention the significance of both the events.Preview
  35. Q35a. How many spermatozoa are formed from one secondary spermatocyte? b. Where does the first cleavage division of zygote take place?Preview
  36. Q36Corpus luteum in pregnancy has a long life. However, if fertilisation does not take place, it remains active only for 10-12 days. Explain.Preview
  37. Q37What is foetal ejection reflex? Explain how it leads to parturition?Preview
  38. Q38Except endocrine function, what are the other functions of placenta.Preview
  39. Q39Why doctors recommend breast feeding during initial period of infant growth?Preview
  40. Q40What are the events that take place in the ovary and uterus during follicular phase of the menstrual cycle.Preview
  41. Q41Given below is a flow chart showing ovarian changes during menstrual cycle. Fill in the spaces giving the name of the hormones responsible f…Preview
  42. Q42Give a schematic labelled diagram to represent oogenesis (without descriptions).Preview
  43. Q43What are the changes in the oogonia during the transition of a primary follicle to Graafian follicle?Preview
  44. Q44What role does pituitary gonadotropins play during follicular and ovulatory phases of menstrual cycle? Explain the shifts in steroidal secre…Preview
  45. Q45Meiotic division during oogenesis is different from that in spermatogenesis. Explain how and why?Preview
  46. Q46The zygote passes through several developmental stages till implantation. Describe each stage briefly with suitable diagrams.Preview
  47. Q47Draw a neat diagram of the female reproductive system and label the parts associated with the following (a) production of gamete, (b) site o…Preview
  48. Q48With a suitable diagram, describe the organisation of mammary gland.Preview

Sample & Board Papers

Sample papers and previous-year board questions for this subject.

+Show 1 question1 question
  1. Q1Draw a diagram of a mature human sperm. Label any three parts and write their functions.Preview

More questions

7 Q
+Show 6 questions6 questions
  1. Q1What would be the number of chromosome in the spermatids?Free
  2. Q2Can you think of any advantage for this? (The secondary oocyte retaining bulk of the nutrient-rich cytoplasm of the primary oocyte, while th…Free
  3. Q3Does the first polar body born out of first meiotic division divide further or degenerate?Preview
  4. Q4How many chromosomes will be there in the zygote?Preview
  5. Q5What are the major features of embryonic development at various months of pregnancy?Preview
  6. Q6What do you think the doctors inject to induce delivery?Preview
+Show 1 question1 question
  1. Q1Do you know for how many months pregnancy last in dogs, elephants, cats? Find out.Preview