Class 10th Science Chapter 7 – How Do Organisms Reproduce? | Sexual Reproduction in Human Beings

How Do Organisms Reproduce?

Sexual Reproduction in Human Beings | Class 10 Science | CBSE + Foundation + Competitive Level

Sexual Reproduction in Human Beings

1. Introduction to Sexual Reproduction

Sexual reproduction is a mode of reproduction in which male and female gametes are produced and their fusion leads to the formation of a new organism.

यौन जनन (Sexual Reproduction) वह जनन प्रक्रिया है जिसमें नर और मादा युग्मक (gametes) बनते हैं तथा उनके संलयन से नए जीव का निर्माण होता है।

In human beings, sexual reproduction involves two types of gametes:

• Sperm – male gamete / नर युग्मक
• Ovum (egg) – female gamete / मादा युग्मक

Sperm → Ovum → Fertilisation → Zygote → Embryo → Foetus

2. Puberty and Adolescence

Puberty is the stage when the reproductive organs become mature and the body starts showing reproductive characteristics.

यौवनारंभ (Puberty) वह अवस्था है जब जनन अंग परिपक्व होने लगते हैं और शरीर में लैंगिक परिवर्तन दिखाई देने लगते हैं।

Major changes during puberty:

• Growth of reproductive organs.
• Production of sperm in males.
• Maturation and release of ova in females.
• Development of secondary sexual characteristics.
• Hormonal changes.

3. Male Reproductive System

The male reproductive system is specialised for:

• Production of sperm.
• Secretion of male sex hormones.
• Transport and delivery of sperm.

Major Parts

Part	Function	हिंदी
Testes	Produce sperm and testosterone.	शुक्राणु तथा टेस्टोस्टेरोन का निर्माण।
Scrotum	Holds testes outside the abdominal cavity and helps maintain a suitable lower temperature for sperm formation.	वृषणों को शरीर के बाहर रखता है तथा उपयुक्त तापमान बनाए रखने में सहायता करता है।
Epididymis	Site where sperm mature and are stored.	शुक्राणुओं के परिपक्व होने और संग्रह में सहायता।
Vas deferens	Transports sperm.	शुक्राणुओं का परिवहन।
Seminal vesicles	Add fluid rich in nutrients to semen.	वीर्य में पोषक द्रव मिलाती हैं।
Prostate gland	Adds alkaline fluid to semen.	वीर्य में क्षारीय द्रव मिलाती है।
Urethra	Common passage for urine and semen at different times.	मूत्र तथा वीर्य के लिए मार्ग।
Penis	Transfers semen into the female reproductive tract.	वीर्य को मादा जनन मार्ग में पहुँचाता है।

Animated Simplified Male Reproductive System

Exam Tip: Testes are located in the scrotum because sperm formation requires a temperature slightly lower than the normal body temperature.

4. Testes – Structure and Functions

The testes are the male reproductive organs. They perform two important functions:

1. Production of sperm.
2. Production of testosterone.

Sperm are produced inside the seminiferous tubules of the testes.

Testosterone is the main male sex hormone. It contributes to development of male reproductive organs and secondary sexual characteristics and supports sperm production.

5. Structure of Sperm

A sperm is a microscopic male gamete specially adapted for reaching and fertilising the ovum.

Part	Function
Head	Contains nucleus carrying genetic material.
Acrosome	Contains enzymes that help sperm penetrate the egg coverings.
Middle piece	Contains many mitochondria that provide energy.
Tail	Helps in movement of sperm.

6. Female Reproductive System

The female reproductive system produces ova, provides the site for fertilisation and supports development of the embryo and foetus.

Part	Function	हिंदी
Ovaries	Produce ova and female sex hormones.	अंडाणु तथा महिला लैंगिक हार्मोन बनाती हैं।
Fallopian tubes / Oviducts	Carry ovum; fertilisation usually occurs here.	अंडाणु का परिवहन; सामान्यतः निषेचन यहीं होता है।
Uterus	Site where embryo implants and develops.	भ्रूण के आरोपण और विकास का स्थान।
Cervix	Lower narrow part of uterus opening into vagina.	गर्भाशय का निचला संकरा भाग।
Vagina	Receives semen and acts as the birth canal.	वीर्य ग्रहण करती है तथा जन्म मार्ग का कार्य करती है।

Animated Simplified Female Reproductive System

7. Ovaries and Ovum

The ovaries are the primary female reproductive organs. They produce ova and secrete female sex hormones such as estrogen and progesterone.

Usually, one mature ovum is released from an ovary during a menstrual cycle. This process is called ovulation.

Ovulation = release of a mature egg/ovum from an ovary.

8. Menstrual Cycle

The menstrual cycle is a cyclic series of changes in the female reproductive system. A typical cycle is often described as about 28 days, but the actual length can vary among individuals.

If fertilisation does not occur, the thickened uterine lining breaks down and is discharged as menstrual flow.

This process is called menstruation.

Process	Meaning
Follicular phase	Follicle develops and the uterine lining begins to build up.
Ovulation	Release of mature ovum from ovary.
Luteal phase	Hormonal changes maintain the uterine lining.
Menstruation	Uterine lining is shed if pregnancy has not occurred.

9. Fertilisation in Human Beings

Fertilisation is the fusion of a male gamete (sperm) with a female gamete (ovum) to form a zygote.

In humans, fertilisation normally occurs in the fallopian tube / oviduct.

Sperm + Ovum → Zygote

The zygote contains genetic material from both parents.

10. Steps of Fertilisation

1. Sperm are released into the female reproductive tract.
2. Sperm travel towards the fallopian tube.
3. A sperm reaches the ovum.
4. The sperm penetrates the egg coverings.
5. The genetic material of sperm and ovum combines.
6. A diploid zygote is formed.

Animated Concept of Fertilisation

11. Zygote Formation and Development

After fertilisation, the zygote undergoes repeated cell divisions. It develops into an embryo.

Zygote → Cell Division → Embryo → Implantation → Foetus

The embryo becomes attached to the uterine wall. This process is called implantation.

12. Placenta and Foetal Nutrition

The placenta is a specialised temporary structure that develops between the mother and the developing embryo/foetus.

It helps in:

• Supply of oxygen to the developing foetus.
• Supply of nutrients.
• Removal of carbon dioxide.
• Removal of certain metabolic wastes.
• Exchange of substances between maternal and foetal blood systems.

Important: Maternal and foetal blood do not normally mix directly; exchange occurs across the placental tissues.

13. Embryo and Foetus

The developing organism is called an embryo during the early stages of development. As body parts become more distinctly developed, it is called a foetus.

The embryo/foetus receives oxygen and nutrients through the placenta.

14. Sex Determination in Human Beings

Humans have 46 chromosomes (23 pairs) in most body cells. One pair is the sex chromosomes.

Individual	Sex Chromosomes	Gametes
Female	XX	Only X-bearing ova
Male	XY	X-bearing or Y-bearing sperm

The ovum always contributes an X chromosome. A sperm contributes either X or Y.

X ovum + X sperm → XX

X ovum + Y sperm → XY

Therefore, the sperm determines the chromosomal sex of the child in the XX–XY system.

15. Important Hormones

Hormone	Major Role
Testosterone	Male reproductive development, secondary sexual characteristics and support of sperm production.
Estrogen	Female reproductive development and regulation of reproductive processes.
Progesterone	Helps prepare and maintain the uterine lining, especially during pregnancy.
FSH	Helps regulate development of ovarian follicles and sperm production.
LH	Important in ovulation and reproductive hormone regulation; in males it supports testosterone production by stimulating Leydig cells.

16. Sexual and Asexual Reproduction – Comparison

Feature	Asexual Reproduction	Sexual Reproduction
Parents	Usually one	Usually involves two parents
Gametes	Not involved	Male and female gametes involved
Fertilisation	Absent	Present
Variation	Usually less	Generally greater
Genetic material	Usually from one parent	Combines from two parents

17. Importance of Sexual Reproduction

• Produces genetic variation.
• Combines genetic material from two parents.
• Variation can help populations adapt to changing environments.
• Contributes to evolution over generations.

18. Complete Concept Map

Puberty → Gamete Formation → Sperm + Ovum → Fertilisation → Zygote → Embryo → Implantation → Foetus

19. MCQs – CBSE + Foundation + Competitive Level

Q1. The male gamete in human beings is:

A) Ovum

B) Sperm

C) Zygote

D) Embryo

Answer: B) Sperm

Sperm is the male reproductive gamete.

Q2. The female gamete in humans is called:

A) Ovum

B) Sperm

C) Embryo

D) Foetus

Answer: A) Ovum

The mature female gamete is the ovum or egg.

Q3. Fertilisation in humans normally occurs in the:

A) Uterus

B) Ovary

C) Fallopian tube

D) Vagina

Answer: C) Fallopian tube

Fusion of sperm and ovum normally takes place in the oviduct/fallopian tube.

Q4. The hormone mainly associated with male reproductive development is:

A) Testosterone

B) Estrogen

C) Insulin

D) Thyroxine

Answer: A) Testosterone

Q5. Which organ produces both sperm and testosterone?

A) Prostate gland

B) Testes

C) Urethra

D) Seminal vesicle

Answer: B) Testes

Q6. The scrotum helps sperm formation mainly by:

A) Increasing body temperature

B) Maintaining a suitable lower temperature for testes

C) Producing ova

D) Producing urine

Answer: B) Maintaining a suitable lower temperature for testes

Q7. Which structure carries sperm away from the epididymis?

A) Vas deferens

B) Ureter

C) Fallopian tube

D) Cervix

Answer: A) Vas deferens

Q8. Which female organ produces ova?

A) Uterus

B) Ovary

C) Vagina

D) Cervix

Answer: B) Ovary

Q9. The embryo becomes attached to the uterine wall by:

A) Ovulation

B) Menstruation

C) Implantation

D) Ejaculation

Answer: C) Implantation

Q10. The immediate product of fertilisation is:

A) Foetus

B) Embryo

C) Zygote

D) Placenta

Answer: C) Zygote

Q11. Which chromosome combination is normally associated with a human female?

A) XY

B) YY

C) XO

D) XX

Answer: D) XX

Q12. Which type of sperm can be produced by a normal human male?

A) Only X-bearing

B) Only Y-bearing

C) X-bearing or Y-bearing

D) X- and Y-bearing in the same sperm

Answer: C) X-bearing or Y-bearing

Q13. The organ that supports development of the embryo is:

A) Uterus

B) Ovary

C) Testis

D) Epididymis

Answer: A) Uterus

Q14. The placenta mainly helps in:

A) Producing sperm

B) Exchange of nutrients and gases

C) Producing urine

D) Producing ova

Answer: B) Exchange of nutrients and gases

Q15. Menstruation occurs when:

A) Fertilisation occurs

B) Pregnancy begins

C) Fertilisation does not occur and the uterine lining is shed

D) Sperm are produced

Answer: C)

Q16. Ovulation refers to:

A) Formation of sperm

B) Release of a mature ovum

C) Fusion of gametes

D) Implantation

Answer: B) Release of a mature ovum

Q17. Which structure receives sperm during sexual intercourse?

A) Vagina

B) Ovary

C) Uterus only

D) Kidney

Answer: A) Vagina

Q18. Which gland contributes fluid to semen?

A) Thyroid

B) Prostate gland

C) Pituitary only

D) Adrenal gland

Answer: B) Prostate gland

Q19. The genetic material of a zygote comes from:

A) Mother only

B) Father only

C) Both parents

D) Placenta only

Answer: C) Both parents

Q20. Sexual reproduction generally produces more variation because:

A) DNA is never copied

B) Genetic material from two parents combines

C) Only one parent contributes genes

D) Gametes do not form

Answer: B)

Q21. A human ovum normally contains:

A) 46 chromosomes

B) 23 chromosomes

C) 92 chromosomes

D) 44 chromosomes

Answer: B) 23 chromosomes

Q22. A normal human sperm contains:

A) 23 chromosomes

B) 46 chromosomes

C) 92 chromosomes

D) 44 pairs

Answer: A) 23 chromosomes

Q23. If an X-bearing sperm fertilises an ovum, the zygote will normally be:

A) XY

B) XX

C) YY

D) XO

Answer: B) XX

Q24. If a Y-bearing sperm fertilises an ovum, the zygote will normally be:

A) XX

B) YY

C) XY

D) XO

Answer: C) XY

Q25. Which statement about the uterus is correct?

A) It produces sperm

B) It is the usual site of implantation

C) It produces ova

D) It carries sperm from testes

Answer: B)

Q26. Which sequence is correct?

A) Ovum → zygote → sperm → embryo

B) Sperm + ovum → zygote → embryo

C) Embryo → sperm → zygote

D) Zygote → sperm → ovum

Answer: B)

Q27. Which of the following is a secondary sexual characteristic in males?

A) Production of urine

B) Deepening of voice

C) Formation of red blood cells

D) Digestion of food

Answer: B)

Q28. Which hormone is mainly secreted by the testes?

A) Testosterone

B) Estrogen

C) Progesterone

D) Thyroxine

Answer: A)

Q29. Which event directly restores the diploid chromosome number?

A) Ovulation

B) Sperm formation

C) Fertilisation

D) Menstruation

Answer: C) Fertilisation

Q30. The greatest significance of sexual reproduction is:

A) No genetic variation

B) Production of identical offspring

C) Generation of genetic variation

D) Absence of gametes

Answer: C) Generation of genetic variation

20. Subjective Questions with Answers

2 Marks Q1. What is sexual reproduction?

Sexual reproduction is a mode of reproduction involving male and female gametes. Their fusion forms a zygote.
हिंदी: नर और मादा युग्मकों के संलयन द्वारा नए जीव के निर्माण की प्रक्रिया यौन जनन कहलाती है।

2 Marks Q2. Name the male and female gametes in humans.

Male gamete – Sperm.
Female gamete – Ovum/egg.

2 Marks Q3. What is fertilisation?

Fertilisation is the fusion of a sperm and an ovum to form a zygote.

2 Marks Q4. What is puberty?

Puberty is the stage when reproductive organs mature and secondary sexual characteristics begin to develop.

2 Marks Q5. Name two functions of testes.

1. Production of sperm.
2. Secretion of testosterone.

3 Marks Q6. Write three functions of the female reproductive system.

• Produces ova.
• Provides the usual site for fertilisation.
• Supports implantation and development of embryo/foetus.

3 Marks Q7. Why are testes located in the scrotum?

The scrotum keeps the testes outside the main body cavity and helps maintain a temperature slightly lower than normal body temperature, which is suitable for sperm formation.

3 Marks Q8. What is ovulation?

Ovulation is the release of a mature ovum from an ovary. It usually occurs around the middle of a menstrual cycle, although its timing can vary.

3 Marks Q9. Explain implantation.

After fertilisation, the zygote divides and forms an embryo. The embryo attaches to the lining of the uterus. This attachment is called implantation.

3 Marks Q10. What is the role of placenta?

Placenta helps in the exchange of oxygen, nutrients and waste substances between the mother and developing foetus.

4 Marks Q11. Describe the functions of the male reproductive system.

• Testes produce sperm.
• Testes secrete testosterone.
• Accessory glands add fluids to sperm to form semen.
• Vas deferens and urethra help transport semen.

4 Marks Q12. Explain the functions of the ovary.

The ovary:

• Produces ova.
• Releases mature ova during ovulation.
• Produces estrogen.
• Produces progesterone, especially through ovarian tissues involved in the cycle.

4 Marks Q13. Differentiate between sperm and ovum.

Sperm	Ovum
Male gamete	Female gamete
Very small	Much larger
Motile due to tail	Non-motile in the usual sense
Produced in testes	Produced in ovaries

4 Marks Q14. Explain the menstrual cycle briefly.

The menstrual cycle involves maturation of an ovarian follicle, ovulation and preparation of the uterine lining. If fertilisation does not occur, the uterine lining breaks down and is shed as menstruation. The timing and length can vary among individuals.

4 Marks Q15. Explain sex determination in humans.

Females normally have XX chromosomes and produce ova carrying X. Males normally have XY chromosomes and produce X-bearing or Y-bearing sperm. X sperm + X ovum produces XX, while Y sperm + X ovum produces XY.

5 Marks Q16. Describe the male reproductive system.

The male reproductive system consists of testes, scrotum, epididymis, vas deferens, accessory glands, urethra and penis. Testes produce sperm and testosterone. Sperm mature and are stored in the epididymis. Vas deferens transports sperm. Seminal vesicles and prostate add fluids to form semen. Urethra and penis help in transfer of semen.

5 Marks Q17. Describe the female reproductive system.

The female reproductive system consists mainly of ovaries, fallopian tubes, uterus, cervix and vagina. Ovaries produce ova and hormones. Fallopian tubes carry ova and are the usual site of fertilisation. The uterus supports implantation and development of the embryo. The cervix connects the uterus to the vagina, which receives semen and also acts as the birth canal.

5 Marks Q18. Explain fertilisation and development of the embryo.

A sperm fuses with an ovum in the fallopian tube to form a zygote. The zygote undergoes repeated cell division and forms an embryo. The embryo moves towards the uterus and implants in its lining. It develops further and receives oxygen and nutrients through the placenta.

5 Marks Q19. Explain the importance of sexual reproduction.

Sexual reproduction combines genetic material from two parents. This creates genetic variation among offspring. Such variation provides the raw material for natural selection and can help populations adapt to environmental changes.

5 Marks Q20. Explain the role of hormones in human reproduction.

Hormones regulate development and functioning of reproductive organs. Testosterone supports male reproductive development and sperm production. Estrogen and progesterone regulate important female reproductive processes, including development of the reproductive system and preparation of the uterine lining.

6 Marks Q21. Explain the complete process of sexual reproduction in human beings.

The process involves:

1. Puberty and maturation of reproductive organs.
2. Production of sperm and ova.
3. Transfer of sperm into the female reproductive tract.
4. Fertilisation in the fallopian tube.
5. Formation and division of the zygote.
6. Implantation of embryo in uterus and development through the foetal stage.

6 Marks Q22. Explain the structure and functions of the male reproductive system.

Testes produce sperm and testosterone. The scrotum maintains suitable temperature. Epididymis helps sperm maturation and storage. Vas deferens transports sperm. Seminal vesicles and prostate gland add fluids to form semen. Urethra provides a passage for semen, and the penis transfers semen into the female reproductive tract.

6 Marks Q23. Explain the structure and functions of the female reproductive system.

Ovaries produce ova and hormones. Fallopian tubes transport ova and are the usual site of fertilisation. The uterus receives the embryo and supports its development. The cervix is the lower part of the uterus. The vagina receives semen and serves as the birth canal.

6 Marks Q24. Describe the events from fertilisation to formation of foetus.

Sperm and ovum fuse to form a zygote. The zygote divides repeatedly, forming an embryo. The embryo reaches the uterus and implants in its lining. The developing organism receives nutrients and oxygen through the placenta. As development progresses and body parts become more distinctly developed, it is referred to as a foetus.

6 Marks Q25. Explain sex determination using a suitable cross.

Female = XX → ova contain X.
Male = XY → sperm contain X or Y.

	X sperm	Y sperm
X ovum	XX	XY

Thus, the sperm contributes either X or Y chromosome, while the ovum contributes X.

6 Marks Q26. Explain the importance of placenta in human reproduction.

Placenta provides a large exchange surface between maternal and foetal circulations. It allows nutrients and oxygen to reach the developing foetus and helps remove carbon dioxide and certain wastes. It also acts as an important endocrine tissue during pregnancy by producing hormones that support pregnancy.

6 Marks Q27. Differentiate between sexual and asexual reproduction.

Sexual Reproduction	Asexual Reproduction
Gametes involved	Gametes generally not involved
Fertilisation may occur	Fertilisation absent
Usually involves genetic contribution from two parents	Usually one parent
Generally produces more variation	Usually produces less variation

6 Marks Q28. Why is sexual reproduction important for evolution?

Sexual reproduction combines genetic material from two individuals. Recombination and other genetic processes generate variation in offspring. Some variations may provide advantages in particular environments. Over generations, natural selection can increase advantageous variations, contributing to evolutionary change.

6 Marks Q29. Explain the role of testes, ovaries and reproductive hormones.

Testes produce sperm and testosterone. Ovaries produce ova and female reproductive hormones such as estrogen and progesterone. These hormones regulate reproductive development, secondary sexual characteristics, gamete-related processes and preparation of the female reproductive system for possible pregnancy.

6 Marks Q30. Draw and label the male and female reproductive systems and state their major functions.

Male labels: Testis, scrotum, epididymis, vas deferens, seminal vesicle, prostate gland, urethra and penis.

Female labels: Ovary, fallopian tube, uterus, cervix and vagina.

Major functions: Male system produces and transports sperm; female system produces ova, provides the usual site of fertilisation and supports embryo development.

21. HOTS / Competency-Based Questions

HOTS 1: If the vas deferens is blocked, which reproductive process will be directly affected?

Answer: Transport of sperm from the epididymis towards the urethra will be affected.

HOTS 2: Why can a female ovum be fertilised only after reaching the appropriate region of the oviduct?

The oviduct provides the normal location where sperm and ovum can meet and fertilisation can occur.

HOTS 3: Why does sexual reproduction generally create more variation than asexual reproduction?

Because genetic material from two parents combines and genetic variation can arise during gamete formation and fertilisation.

HOTS 4: A child has an XX chromosome combination. What type of sperm fertilised the ovum?

An X-bearing sperm fertilised the X-bearing ovum.

HOTS 5: Why is implantation necessary?

Implantation establishes the embryo within the uterine lining so that it can receive support and nutrients through the developing placenta.

22. Important Diagram Labelling

Male Reproductive System – Labels

1. Testis
2. Scrotum
3. Epididymis
4. Vas deferens
5. Seminal vesicle
6. Prostate gland
7. Urethra
8. Penis

Female Reproductive System – Labels

1. Ovary
2. Fallopian tube / Oviduct
3. Uterus
4. Cervix
5. Vagina

23. CBSE Golden Points

Testes → Sperm + Testosterone Ovary → Ovum + Hormones Sperm + Ovum → Zygote Fertilisation → Fallopian Tube Implantation → Uterus Placenta → Exchange Female → XX Male → XY

• Human sexual reproduction involves male and female gametes.
• Testes produce sperm and testosterone.
• Ovaries produce ova and female sex hormones.
• Fertilisation normally occurs in the fallopian tube.
• Zygote is the first cell formed after fertilisation.
• Implantation occurs in the uterine lining.
• Placenta helps exchange nutrients and gases.
• Female is normally XX and male is normally XY.
• Ovum always contributes X in the XX–XY system.
• Sperm contributes X or Y.
• Sexual reproduction generates genetic variation.

24. Easy Memory Trick

Male System

T → S → E → V → G → U

Testes → Sperm → Epididymis → Vas deferens → Glands → Urethra

Female System

O → F → U → C → V

Ovary → Fallopian tube → Uterus → Cervix → Vagina

Reproduction Flow

Sperm + Ovum → Zygote → Embryo → Implantation → Foetus

25. One-Line Revision

Human sexual reproduction involves formation of sperm and ova, fertilisation in the fallopian tube, zygote formation, implantation in the uterus and development of the embryo/foetus with support from the placenta.

26. Final Summary

• Sexual reproduction involves male and female gametes.
• Sperm are produced in the testes.
• Ova are produced in the ovaries.
• Testes secrete testosterone.
• Ovaries secrete estrogen and progesterone.
• Fertilisation normally occurs in the fallopian tube.
• Fusion of sperm and ovum forms a zygote.
• The zygote develops into an embryo.
• The embryo implants in the uterine wall.
• Placenta provides exchange of oxygen, nutrients and wastes.
• XX is the usual chromosomal combination in females.
• XY is the usual chromosomal combination in males.
• The sperm determines whether the zygote receives X or Y from the father.
• Sexual reproduction generates variation.