Maharashtra Board Class 12 Biology Chapter 2 Reproduction in Lower and Higher Animals Solutions

Multiple Choice Questions

Question 1. The number of nuclei present in a zygote is ……………….
(a) two
(b) one
(c) four
(d) eight
Answer: (b) one
In simple words: A zygote is formed when a sperm and an egg fuse together. Their two individual nuclei merge into a single nucleus, so the resulting zygote contains only one nucleus.

🎯 Exam Tip: Remember that even though two gametes fuse, their nuclei merge completely to form a single diploid nucleus in the zygote.

Question 2. Which of these is the male reproductive organ in human?
(a) Sperm
(b) Seminal fluid
(c) Testes
(d) Ovary
Answer: (c) Testes
In simple words: Testes are the main male reproductive organs because they are responsible for producing sperm and male sex hormones.

🎯 Exam Tip: Do not confuse gametes (like sperm) or reproductive fluids (like seminal fluid) with the actual organ (testes) that produces them.

Question 3. Attachment of embryo to the wall of the uterus is known as ……………….
(a) fertilization
(b) gestation
(c) cleavage
(d) implantation
Answer: (d) implantation
In simple words: Implantation is the process where the early embryo attaches itself to the inner wall of the uterus so it can receive nutrients and grow.

🎯 Exam Tip: Be sure to distinguish between fertilization (fusion of gametes), cleavage (cell division), implantation (attachment), and gestation (the pregnancy period).

Question 4. Rupturing of follicles and discharge of ova is known as ……………….
(a) capacitation
(b) gestation
(c) ovulation
(d) copulation
Answer: (c) ovulation
In simple words: Ovulation is the process where a mature egg is released from the ovary, making it ready for fertilization.

🎯 Exam Tip: Remember that ovulation is triggered by a surge in Luteinizing Hormone (LH), which is a key concept often tested in exams.

Question 5. In human females, the fertilized egg gets implanted in uterus ……………….
(a) after about 7 days of fertilization
(b) after about 30 days of fertilization
(c) after about two months of fertilization
(d) after about 3 weeks of fertilization
Answer: (a) after about 7 days of fertilization
In simple words: After an egg is fertilized, it takes about a week to travel down to the uterus and attach itself to the wall to grow.

🎯 Exam Tip: Memorize the timeline of early embryonic development; implantation typically occurs 6 to 9 days (roughly a week) after fertilization.

Question 6. Test tube baby technique is called ……………….
(a) In vivo fertilization
(b) In situ fertilization
(c) In Vitro Fertilization
(d) Artificial Insemination
Answer: (c) In Vitro Fertilization
In simple words: "In vitro" means "in glass" (like a laboratory dish), where the egg and sperm are joined outside the mother's body.

🎯 Exam Tip: Do not confuse IVF (fertilization outside the body) with artificial insemination (where sperm is introduced directly inside the female reproductive tract).

Question 7. The given figure shows a human sperm. Various parts of it are labelled as A, B, C, and D. Which labelled part represents acrosome?
The diagram labels represent:

• A - Acrosome
• B - Head / Nucleus
• C - Middle piece
• D - Tail

🎯 Exam Tip: Remember that the acrosome contains enzymes essential for fertilizing the egg, so it is always located at the very tip (Label A).

Question 8. Presence of beard in boys is a ……………….
(a) primary sex organ
(b) secondary sexual character
(c) secondary sex organ
(d) primary sexual character
Answer: (b) secondary sexual character
In simple words: Physical changes like growing a beard or a deeper voice that happen during puberty are called secondary sexual characteristics.

🎯 Exam Tip: Do not confuse primary characters (present at birth) with secondary characters (develop during puberty like facial hair and voice changes).

2. Very Short Answer Questions

Question 1. What is the difference between a foetus and an embryo?
Answer: Embryo is a growing egg after fertilization until the main parts of the body and the internal organs have started to take shape while foetus is a stage which has the appearance of a fully developed offspring. This developmental transition marks a significant milestone in prenatal growth.
In simple words: An embryo is the early stage of a baby when its body parts are just starting to form. A foetus is the later stage when it actually looks like a tiny, fully formed baby.

🎯 Exam Tip: Clearly define the timeline or structural differences to score full marks; remember that embryo comes first, followed by the foetus stage.

Question 2. Outline the path of sperm up to the urethra.
Answer: The path of sperm up to the urethra in male is as follows: Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra. This sequential pathway ensures the safe maturation and transport of sperm cells.
In simple words: Sperm travels from the testicles where they are made, through a series of tiny tubes and storage areas, until they reach the urethra to leave the body.

🎯 Exam Tip: Draw a simple flow chart using arrows to represent the pathway clearly, as examiners love structured flow diagrams.

Question 3. Which glands contribute fluids to the semen?
Answer: The glands which contribute fluids to the semen are seminal vesicles, prostate gland. These secretions help in nourishing and transporting the sperm.
In simple words: Semen is made of sperm and fluids from different glands. The seminal vesicles and prostate gland are the main glands that add these helpful fluids.

🎯 Exam Tip: Mention both the seminal vesicles and the prostate gland to get full marks, as these are the primary accessory glands.

Question 4. Name the endocrine glands involved in maintaining the sexual characteristics of males.
Answer: Interstitial cells of Leydig which lie in between the seminiferous tubules are involved in maintaining the sexual characteristics of male by secreting the male hormone androgen or testosterone. Adenohypophysis also regulates this secretion from the testis. This hormonal balance is crucial for normal male reproductive health.
In simple words: The Leydig cells in the testes make testosterone, which gives males their male features. The pituitary gland in the brain controls this process.

🎯 Exam Tip: Do not forget to mention the pituitary gland (adenohypophysis) along with the Leydig cells, as both are endocrine structures involved in this pathway.

Question 5. Where does fertilization and implantation occur?
Answer: Fertilization of ovum takes place in the ampulla region of fallopian tube whereas implantation occur in the endometrium of uterus. This ensures the developing embryo is safely housed and nourished.
In simple words: Fertilization (when sperm meets egg) happens in the fallopian tube. Implantation (when the egg attaches to grow) happens in the wall of the uterus.

🎯 Exam Tip: Be specific with the locations: use "ampulla of the fallopian tube" for fertilization and "endometrium of the uterus" for implantation.

Question 6. Enlist the external genital organs in female.
Answer: The external genital organs in female include the following parts such as vestibule, labia minora, clitoris, labia majora and mons Veneris. Together, these structures are collectively referred to as the vulva.
In simple words: The outer parts of the female reproductive system include the vestibule, labia minora, clitoris, labia majora, and mons Veneris.

🎯 Exam Tip: Memorize all five parts and write them as a clear list to secure full marks.

Question 8. What is the difference between embryo and zygote?
Answer: Zygote is the unicellular diploid structure formed as a result of fusion of sperm and ovum whereas embryo is a multicellular structure formed from zygote in the uterus 3 weeks after fertilization. This transition marks the beginning of complex organ development.
In simple words: A zygote is a single cell formed right when the sperm and egg join. An embryo is a group of many cells that grows from the zygote later on.

🎯 Exam Tip: Highlight the key difference in cell number: zygote is unicellular (one cell) while embryo is multicellular (many cells).

Fill in the Blanks

Question 1. The primary sex organ in human male is ……………….
Answer: testis. It is responsible for producing sperm and male sex hormones.
In simple words: The testes are the main male reproductive organs that make sperm.

🎯 Exam Tip: Remember that the testes perform dual functions: producing male gametes (sperm) and secreting the hormone testosterone.

Question 2. The ……………… is also called the womb.
Answer: uterus. This muscular organ supports the development of the baby during pregnancy.
In simple words: The uterus is the place inside a mother's body where a baby grows before birth.

🎯 Exam Tip: Always associate the term 'womb' with the uterus, as this is a common one-mark question in exams.

Question 3. Sperm fertilizes ovum in the ……………….. of fallopian tube.
Answer: ampulla. This is the specific site where fertilization typically occurs.
In simple words: The ampulla is the middle, wider part of the fallopian tube where the egg and sperm meet.

🎯 Exam Tip: Be precise; do not just write 'fallopian tube' if the question asks for the specific region, which is the ampulla.

Question 4. The disc like structure which helps in the transfer of substances to and from the foetus’s body is called ………………..
Answer: placenta. It provides oxygen and nutrients to the growing baby while removing waste products.
In simple words: The placenta is a special connection between the mother and the baby that helps feed the baby and clean its blood.

🎯 Exam Tip: Mention both functions of the placenta—nutrition supply and waste removal—to secure full marks in descriptive questions.

Question 5. Gonorrhoea is caused by ……………….. bacteria.
Answer: Neisseria gonorrhoeae. This bacterium is responsible for the sexually transmitted infection.
In simple words: Gonorrhoea is a disease caused by a specific type of bacteria called Neisseria gonorrhoeae.

🎯 Exam Tip: Always write scientific names like Neisseria gonorrhoeae clearly and ensure the genus starts with a capital letter.

Question 6. The hormone produced by the testis is ……………………
Answer: testosterone / androgen. These hormones regulate male reproductive development and secondary sexual characteristics.
In simple words: Testosterone is the main male hormone made by the testes that helps boys develop male features.

🎯 Exam Tip: Writing either 'testosterone' or 'androgen' is correct, but 'testosterone' is the most widely accepted and preferred term.

Short Answer Questions

Question 1. Budding in Hydra.
Answer: Budding in Hydra is a form of asexual reproduction where a small outgrowth or bud develops due to repeated cell division at one specific site. This bud grows into a tiny individual, develops tentacles and a mouth, and eventually detaches from the parent body to live independently.
In simple words: Budding is when a tiny new Hydra grows directly out of the parent's body like a small branch, then splits off to live on its own.

🎯 Exam Tip: Draw a neat, labeled diagram showing the stages of budding in Hydra to secure full marks in short answer questions.

Question 1. Describe the process of budding in Hydra.
Answer:
The stages of budding in Hydra are:
• Bud
• Developing bud
• Fully mature bud
• Young Hydra separates

1. Budding is a type of asexual reproduction method seen in Hydra. Budding is highly efficient under optimal environmental conditions.
2. Budding takes place during favourable period.
3. Towards the basal end of the body, small outgrowth is produced which is called a bud.
4. It grows and forms tentacles and gradually forms a new individual.
5. The young Hydra after complete development detaches from the parent and becomes an independent new organism.
In simple words: Budding is when a small part of the parent Hydra grows into a baby Hydra. Once it is fully grown with tentacles, it separates to live on its own.

🎯 Exam Tip: Always list the sequential stages of budding from a simple bud to a separating young Hydra to secure full marks.

Question 2. Explain the different methods of reproduction occurring in sponges.
Answer:
1. Sponges reproduce both asexually and sexually and they also possess the power of regeneration. Their sexual reproduction is similar to higher animals even though their body organization is primitive type. This dual capability ensures their survival in changing aquatic environments.
2. Asexual reproduction in sponges takes place by regeneration, budding and gemmule formation.
3. In sponges, during unfavourable period, gemmule is produced. It is an internal bud.
4. Archaeocytes which are dormant cells are seen in the aggregation in gemmule. These cells are capable of developing into a new organism.
5. Amoebocytes are other cells which secrete thick resistant layer of secretion which is coated around archaeocytes.
6. When favourable conditions of water and temperature return back, the gemmules can develop into new individuals by hatching, e.g. Spongilla.
In simple words: Sponges can reproduce in many ways, including sexually and asexually. During hard times, they form tough internal buds called gemmules that hatch into new sponges when conditions improve.

🎯 Exam Tip: Clearly distinguish between the roles of archaeocytes (which grow into the new sponge) and amoebocytes (which protect them) when explaining gemmule formation.

Question 3. IVF.
Answer:
1. In laboratory under sterile conditions, oocyte and sperms are placed in a test tube or glass plate to form a zygote. This process is called In Vitro Fertilization. This advanced medical procedure has successfully helped many families worldwide.
2. The zygote with 8 blastomeres is then transferred into the fallopian tube for further development.
3. IVF technique is used when childless couple wants to have a baby, but there are issues of sterility.
4. IVF is also called test tube baby technique.
In simple words: IVF is a process where a baby is conceived outside the mother's body in a laboratory dish. Once the egg is fertilized, it is placed back inside the mother to grow into a baby.

🎯 Exam Tip: Be sure to mention that the fertilization occurs under sterile laboratory conditions and specify the 8-blastomere stage for the transfer to get full marks.

Question 4. Comment on any two mechanical contraceptive methods.
Answer:
Two mechanical contraceptive methods are as follows:
A. Condom or Nirodh:
1. It is a protective barrier in the form of thin rubber sheath which is used by male partner during the sexual coitus. It covers the penis and does not allow semen to flow during copulation.
2. Thus the entry of ejaculated semen into the female reproductive tract is obstructed. This can prevent conception. It is a simple and effective method and has no side effects.
3. “Nirodh” is a condom, most widely used in India as a contraceptive by males.
4. Condom also protects both the partners against sexually transmitted diseases such as AIDS and others. These barrier methods are highly recommended for dual protection.

B. Diaphragm, cervical caps and vaults:
1. Diaphragm and cervical caps are to be used by females as mechanical contraceptive measures.
2. They are made up of rubber. They are fitted on the cervix in vagina so that they prevent the entry of sperms into the uterus.
3. They are kept at least six hours after sexual intercourse in order to inhibit sperms from entering female genital tract.
In simple words: Mechanical contraceptives are physical barriers that stop sperm from reaching the egg. Condoms are used by males, while diaphragms and cervical caps are rubber devices used by females.

🎯 Exam Tip: Clearly distinguish between male and female barrier methods, and remember to highlight that condoms also protect against sexually transmitted infections (STIs).

Question 5. Tubectomy.
Answer:
1. The permanent birth control method in women, is called tubectomy.
2. It is a surgical method, also called sterilization.
3. In tubectomy, a small part of the fallopian tube is tied and cut.
4. Tubectomy blocks transport of oocytes and also blocks sperms, thus preventing fertilization from reaching the oocyte. This surgical procedure is highly effective and provides lifelong contraception.
In simple words: Tubectomy is a permanent birth control surgery for women. By cutting and tying the fallopian tubes, it stops the egg and sperm from meeting, which prevents pregnancy.

🎯 Exam Tip: Clearly state that tubectomy involves the fallopian tubes to distinguish it from vasectomy, which involves the vasa deferentia in males.

Question 6. Give the name of causal organism of Syphilis and write on its symptoms.
Answer:
1. Syphilis is a sexually transmitted venereal disease caused by a Spirochaete bacterium Treponema pallidum.
2. The site of infection is the mucous membrane in genital, rectal and oral region.
3. Symptoms of syphilis:
• Primary lesion known as chancre at the site of infection.
• They are seen on the external genitalia in males and inside the vagina in females.
• Skin rashes accompanied by fever, inflamed joints and loss of hair.
• Paralysis
• Degenerative changes in the heart and brain.
If left untreated, the disease can progress through distinct stages and cause severe, irreversible damage to internal organs over several years.
In simple words: Syphilis is a bacterial infection spread through sexual contact. It starts with painless sores, followed by rashes and fever, and can eventually damage the heart and brain if not treated early.

🎯 Exam Tip: Always underline the scientific name of the pathogen, Treponema pallidum, and list the symptoms clearly to score full marks.

Question 7. What is colostrum?
Answer:
1. The fluid secreted by the mammary glands soon after childbirth is called colostrum.
2. Colostrum is the sticky and yellow fluid. It contains proteins, lactose and mother’s antibodies, e.g. IgA.
3. The fat content in colostrum is low.
4. The antibodies present in colostrum helps in developing resistance for the newborn baby at a time when its own immune response is not fully developed. This natural passive immunity is essential for protecting the infant from various environmental pathogens during its first few weeks of life.
In simple words: Colostrum is the thick, yellow milk produced by a mother right after giving birth. It is full of antibodies that help protect the newborn baby from infections while its own immune system is still weak.

🎯 Exam Tip: Do not forget to mention "IgA antibodies" and "passive immunity" as these are the key technical terms examiners look for in this answer.

Answer the Following Questions

Question 1. Describe the phases of menstrual cycle and their hormonal control.
Answer:
Menstrual cycle (Ovarian cycle):
i. Menstrual cycle involves a series of cyclic changes in the ovary and uterus. The cyclic events are regulated by gonadotropins from pituitary and the hormones from ovary.
ii. The cyclic events in woman are repeated within approximately 28 days.
iii. Menstrual cycle is divided into following phases, viz.
1. Menstrual phase (Day 1-5)
2. Follicular phase in ovary that coincides with proliferative phase in uterus. Post menstrual phase (Day 5-14)
3. Ovulatory phase (Day 14-15)
4. Luteal phase in ovary which coincides with secretory phase in uterus (Day 16 to 28).

1. Menstrual Phase:
• Menstrual phase occurs in the absence of fertilization.
• During menstruation, uterine endometrium is sloughed off. Level of progesterone and estrogen decrease during this phase resulting into release of prostaglandins which cause this rupture.
• Blood about 45-100 ml, tissue fluid, mucus, endometrial lining and unfertilized oocyte and other cellular debris is discharged through vagina as a menstrual flow. The endometrial lining becomes about 1 mm thin.
• Fibrinolysin does not allow blood to clot during this period.
• Pituitary starts secreting FSH, which further makes many primordial follicles to develop into primary and few of them into secondary follicles.

2. Proliferative phase/Follicular phase/Post menstrual phase:
• During this phase in the ovary the follicles develop while in uterus the endometrium starts proliferating. Approximately 6 to 12 secondary follicles start developing inside the ovary under the influence of follicle-stimulating hormone.
In simple words: The menstrual cycle is a monthly cycle of changes in a woman's body to prepare for a possible pregnancy. It has four main phases controlled by hormones from the brain and ovaries, starting with the menstrual flow and ending with the preparation of the uterine lining.

🎯 Exam Tip: Clearly list all four phases of the menstrual cycle with their respective day ranges and mention the key hormones like FSH, LH, estrogen, and progesterone to score full marks.

Question 1. Describe the phases of the menstrual cycle.
Answer:
(1) Follicular phase (continued): Developing secondary follicles secrete the hormone estrogen. Estrogen brings about regeneration of endometrium. Further proliferation of endometrium causes formation of endothelial cells, endometrial or uterine glands and network of blood vessels. Endometrium’s thickness becomes 3-5 mm. Usually, only one of them becomes a mature Graafian follicle due to the action of FSH.

(3) Ovulatory phase:
• Ovulation occurs in this phase. Mature Graafian follicle ruptures and secondary oocyte is released into the pelvic region of abdomen.
• Ovulation occurs due to surging quantity of LH from pituitary.

(4) Luteal phase/Secretory phase:
(i) Since the empty Graafian follicle converts itself into corpus luteum under the influence of LH, this phase is called luteal phase in ovary. At the same time, the uterine endometrium thickens and becomes more secretory and hence it is called secretory phase in uterus.
(ii) Corpus luteum secretes progesterone, some amount of estrogens and inhibin. These hormones stimulate the growth of endometrial glands which later start uterine secretions.
(iii) Endometrium becomes more vascularized becomes 8-10 mm. in thickness. These changes are the preparation for the implantation of the ovum if fertilization occurs.
(iv) In absence of fertilization, corpus luteum can survive for only two weeks and then degenerate into a non-secretory white scar called corpus albicans.
(v) If ovum is fertilized, woman becomes pregnant and hormone hCG (human Chorionic Gonadotropin) is secreted by chorionic membrane of embryo which keeps corpus luteum active till the formation of placenta. This complex hormonal interplay ensures that the female reproductive system is perfectly synchronized for potential pregnancy.
In simple words: The menstrual cycle consists of different phases where the body prepares an egg for fertilization and readies the uterus lining. If pregnancy doesn't occur, the lining sheds, and the cycle repeats.

🎯 Exam Tip: Clearly label each phase of the menstrual cycle and mention the key hormones (FSH, LH, estrogen, progesterone) responsible for the changes in each phase to score full marks.

Question 2. Explain the steps of parturition.
Answer: Parturition is the process of giving birth to a baby. This entire process is regulated by a complex neuroendocrine mechanism involving hormones like oxytocin, cortisol, and estrogens. It involves three main steps or stages:
(i) Dilation stage: This is the first and longest stage. Under the influence of oxytocin, uterine contractions begin, causing the cervix to dilate and thin out (efface). The amniotic sac usually ruptures during this stage, releasing the amniotic fluid.
(ii) Expulsion stage: This stage begins with full cervical dilation and ends with the delivery of the baby. Strong uterine contractions, aided by voluntary abdominal contractions of the mother, push the baby out through the vagina (birth canal).
(iii) Placental stage: After the baby is born, the uterus continues to contract mildly to detach and expel the placenta (afterbirth) from the uterine wall. This stage usually lasts for 10 to 45 minutes after delivery.
In simple words: Parturition is the process of childbirth, which happens in three steps: first, the cervix opens up (dilation); second, the baby is pushed out of the mother's body (expulsion); and third, the placenta is delivered (placental stage).

🎯 Exam Tip: Remember to list the three stages in their correct chronological order—Dilation, Expulsion, and Placental—and briefly describe the role of oxytocin in triggering uterine contractions.

Question 2. Describe the process and stages of parturition.
Answer: Parturition involves the following three steps:
1. Dilation stage:
• Dilation stage means dilating the birth canal or passage though which baby is pushed out. In the beginning uterine contractions start from top and baby is moved to cervix. Due to compression of blood vessels and movements of flexible joints in pelvic girdle, mother experiences labour pains.
• Oxytocin is secreted later in more amount causing severe uterine contractions. This pushes baby in a head down position and closer to cervix.
• Cervix and vagina both are dilated.
• This stage lasts for about 12 hours.
• At the end, amniotic sac ruptures and amniotic fluid is passed out.
2. Expulsion stage:
• During second stage of about 20 to 60 minutes, the uterine and abdominal contractions become stronger.
• Foetus moves out with head down position through cervix and vagina.
• The umbilical cord which connects the baby to placenta is tied and cut off close to the baby’s navel.
3. After birth or placental stage : In the last stage of 10 to 45 minutes, once the baby is out then the placenta is also separated from uterine wall and is expelled out as “after birth”. This is accompanied by severe contractions of the uterus. This process is highly regulated by complex neuroendocrine mechanisms involving hormones like oxytocin.
In simple words: Parturition is the process of giving birth, which happens in three stages: opening of the birth canal (dilation), pushing the baby out (expulsion), and finally delivering the placenta (afterbirth).

🎯 Exam Tip: Remember the sequence of the three stages (Dilation, Expulsion, and Placental) along with their average durations to score full marks.

Question 3. Explain the histological structure of testis.
Answer: The histological structure of testis shows the following features:
1. Tunica Albuginea: It is the protective fibrous covering of the testis. It extends inwards as septa, dividing the testis into about 200-300 testicular lobules.
2. Seminiferous Tubules: Each lobule contains 1 to 4 highly coiled seminiferous tubules. These tubules are the sites of sperm production.
3. Germinal Epithelium: The seminiferous tubules are lined by spermatogenic cells (germ cells) that undergo spermatogenesis to form sperms.
4. Sertoli Cells: These are large, pyramidal cells that provide nutrition and support to the developing sperm cells.
5. Leydig Cells (Interstitial Cells): Located in the connective tissue between seminiferous tubules, these cells secrete the male sex hormone, testosterone. These structures work in perfect coordination to ensure successful male gamete production.
In simple words: Inside the testis, there are tiny coiled tubes called seminiferous tubules where sperms are made, supported by Sertoli cells for food, and Leydig cells nearby that produce male hormones.

🎯 Exam Tip: Always draw a neat, labeled diagram showing seminiferous tubules, Leydig cells, and Sertoli cells when answering questions about the histology of the testis.

Histological Structure of Testis

Diagram Labels:

• Tunica albuginea
• Seminiferous tubule
• Interstitial cells (Leydig cells)
• Germinal epithelium
• Basement membrane
• Connective tissue
• Sperm bundle
• Sertoli cell

1. The external covering of testis is a fibrous connective tissue called tunica albuginea.
2. Then there is an incomplete peritoneal covering called tunica vaginalis.
3. Interior to this there is a covering called tunica vascularis formed by capillaries.
4. The testis is composed of many seminiferous tubules that are lined by cuboidal germinal epithelial cells.
5. In the seminiferous tubules various stages of developing sperms are seen as spermatogenesis takes place here. These stages are spermatogonia, primary and secondary spermatocytes, spermatids and sperms.
6. Large, pyramidal sub tentacular cells, nurse cells or Sertoli cells are present between germinal epithelium. Sperm bundles remain attached to Sertoli cells with their heads.
7. Seminiferous tubules form sperms whereas Sertoli cells provide nourishment to the sperms till maturation.
8. In between the seminiferous tubules there are interstitial cells of Leydig which are endocrine in nature. They secrete testosterone.

Question 4. Describe the structure of blastocyst or blastulation

Question 5. Explain the histological structure of ovary in human.
Answer: Histological structure of ovary:
(1) Each ovary is a compact structure differentiated into a central part called medulla and the outer part called cortex. This structural differentiation helps in organizing the blood vessels and developing follicles within the ovary.
In simple words: The human ovary is divided into two main regions: an inner core called the medulla and an outer layer called the cortex where egg cells grow.

🎯 Exam Tip: When describing the histology of the ovary, always mention the division into the outer cortex and inner medulla, as this is a key structural feature examiners look for.

Histology and Structure of the Ovary

(2) The cortex is covered externally by a layer of germinal epithelium while the medulla contains the stroma or loose connective tissue with blood vessels, lymph vessels and nerve fibres.

(3) Different stages of developing ovarian follicles are seen in the cortex. Each primordial follicle has at its centre a large primary oocyte \( 2n \) surrounded by a single layer of flat follicular cells, then gradually it matures.

(4) In the ovary during each menstrual cycle there is a maturation of primordial follicles into multilayered primary, secondary and Graafian follicles.

(5) Every Graafian follicle has three layers, viz. theca externa, theca interna and membrana granulosa which are from outer to inner side. A space called antrum filled with liquor folliculi is present inside the follicle. There is a small hillock of cells called cumulus oophours or discus proligerus over which the ovum is lodged. The ovum in turn is covered by vitelline membrane, zona pellucida and corona radiata from inner side to outer surface.

(6) Ovarian cortex also shows corpus luteum, or yellow body formed from empty Graafian follicle after ovulation. Corpus luteum is converted into corpus albicans or white body in case of absence of conception.

Ovary Structure Diagram Labels:

• Blood vessels
• Primordial follicle (Day 1)
• Primary follicle
• Secondary follicle (Day 12)
• Tertiary follicle
• Mature follicle
• Oocyte
• Medulla
• Ovulated ovum (Day 14)
• Germinal epithelium
• Corpus luteum (Day 20)
• Corpus albicans
• Cortex

Question 6. Describe the various methods of birth control to avoid pregnancy.
Answer: Birth control/Contraceptive methods are of two main types, viz. temporary and permanent.
A. Temporary methods:
In simple words: Birth control methods help prevent unwanted pregnancies and are divided into temporary methods (which can be stopped when you want to have a baby) and permanent methods (which are lifelong solutions).

🎯 Exam Tip: Clearly distinguish between temporary and permanent methods of birth control, and list the key examples of each to secure full marks.

Methods of Contraception

(1) Natural Method/Safe Period/Rhythm Method: A week before and a week after menstrual bleeding is considered the safe period for sexual intercourse. It is based on the fact that ovulation occurs on the 14th day of menstrual cycle.

(2) Coitus Interruptus or Withdrawal: In this method, the male partner withdraws his penis from the vagina before ejaculation, so as to avoid insemination. This method also has some drawbacks, as the pre-ejaculation fluid may contain sperms and this can cause fertilization.

(3) Lactational Amenorrhoea (Absence of Menstruation): This method is based on the fact that ovulation does not occur during the period of intense lactation following parturition so chances of conception are almost negligible. However, this method also has high chances of failure.

(4) Chemical Means (Spermicides): In this method chemicals like foam, tablets, jellies and creams are introduced into the vagina before sexual intercourse, they adhere to the mucous membrane, immobilize and kill the sperms.

(5) Mechanical Means/Barrier Methods:
(i) Condom: It is a thin rubber sheath that is used to cover the penis of the male. Condom should be used before starting coital activity. It also prevents STDs and AIDS.
(ii) Diaphragm, Cervical Caps and Vaults: These devices made of rubber are inserted into the female reproductive tract to cover the cervix during copulation. They prevent conception by blocking the entry of sperms through the cervix.
(iii) Intra-uterine Devices (IUDs): These are plastic or metal objects placed in the uterus by a doctor. These include Lippes loop, copper releasing IUDs (Cu-T, Cu 7, multiload 375) and hormone releasing IUDs (LNG-20, progestasert). They prevent fertilization of the egg or implantation of the embryo.

(6) Physiological (Oral) Devices: Birth control pills (oral contraceptive pills) check ovulation as they inhibit the secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH) that are necessary for ovulation. The pill ‘Saheli’ is taken weekly.

Question 7. What are the goals of RCH programmes?
Answer: Goals of RCH programmes are as follows:
1. Various aspects related to reproduction are made aware to general public.
2. Facilities are provided to people to understand and build up reproductive health.
3. Support is given for building up a reproductively healthy society.
4. Three critical health indicators, i.e. reducing total infertility rate, infant mortality rate and maternal mortality rate are well looked after. These initiatives aim to improve overall community health and well-being.
In simple words: The goals of RCH (Reproductive and Child Health) programmes are to educate people about reproduction, provide healthcare facilities, and reduce health risks for mothers and babies.

🎯 Exam Tip: Remember the full form of RCH (Reproductive and Child Health) and list all three key health indicators to score full marks.

Question 8. What is parturition? Which hormones are involved in parturition?
Answer:
1. Parturition is the act of expelling out the mature foetus from the uterus of mother via the vagina.
2. When the foetus is fully mature, it starts secreting ACTH (Adreno Cortico Trophic Hormone) from its pituitary.
3. ACTH stimulates adrenal glands of foetus to produce corticosteroids.
4. These corticosteroids diffuse from foetal blood to mother’s blood across the placenta. Corticosteroids accumulate in mother’s blood that results in decreased amount of progesterone. Corticosteroids also increase secretion of prostaglandins.
5. Simultaneously estrogen levels rise bringing about initation of contractions of uterine muscular wall.
6. Reduced progesterone level and increased estrogen level cause secretion of oxytocin from mother’s pituitary. This causes greater stimulation of myometrium of uterus. This complex neuroendocrine mechanism ensures the safe delivery of the baby.
In simple words: Parturition is the process of giving birth. It is controlled by hormones like ACTH, corticosteroids, estrogen, and oxytocin, which trigger uterine contractions to push the baby out.

🎯 Exam Tip: Clearly define parturition first, and then list the hormones involved in a step-by-step chronological order to show the complete pathway.

Question 9. What are the functions of male accessory glands?
OR
Write a brief account of accessory sex glands associated with human male reproductive system.
Answer: Seminal Vesicles, prostate gland and Cowper’s glands are associated with human male reproductive system.

(i) Seminal Vesicles:
1. Seminal vesicles occur in pair present on the posterior side of urinary bladder. Its secretion consists about 60% of the total volume of the semen. The secretion is an alkaline seminal fluid containing fructose, fibrinogen and prostaglandins.
2. Fructose helps in the movement of sperms by providing energy to them.
3. Semen is coagulated in bolus by fibrinogen. This helps in faster movements of sperms in vagina after insemination.
4. Reverse peristalsis in vagina and uterus for faster movement of sperms towards the egg in the female body is aided by prostaglandins.

(ii) Prostate gland:
1. It is a single gland located under the urinary bladder. It has about 20 to 30 separate lobes which open separately into the urethra.
2. Prostatic fluid secreted by this gland is milky white and slightly acidic. It forms 30 % of the semen and is secreted in urethra.
3. Its contents are citric acid, acid phosphatase and various other enzymes.
4. The sperms are protected from the acidic environment of vagina by acid phosphatase.

(iii) Cowper’s glands (Bulbo-urethral glands):
1. These are small, pea-sized, paired glands situated on either side of the membranous urethra.
2. They secrete an alkaline, viscous, mucous-like fluid that acts as a lubricant during copulation and neutralizes any remaining acidity in the urethra.
In simple words: The male accessory glands produce fluids that nourish, protect, and help transport sperms, making sure they have enough energy and a safe path to reach the egg.

🎯 Exam Tip: Remember to mention all three glands—Seminal Vesicles, Prostate, and Cowper's—and highlight the specific role of fructose (energy) and alkaline pH (protection) to secure full marks.

Question 10. What is capacitation? Give its importance.
Answer:
1. Capacitation is the process by which the sperms are made capable to swim up to the fallopian tubes. This process takes place in 5-6 hours.
2. 50% of ejaculated sperms die due to unfavourable vaginal and uterine conditions.
3. The remaining sperms are capacitated with the help of prostaglandin and vestibular secretions of female tract. It involves the changes in the membrane covering the acrosome.
4. Due to capacitation, acrosome membrane becomes thin, Calcium ions enters the sperm and their tail begin to show rapid whiplash movements.
5. Sperms become extra active and then they ascend upwards to reach fallopian tubes.
6. After capacitation the sperms swim through the vagina and uterus and reach ampulla of fallopian tube within 5 minutes. An additional physiological change during this process is the dilution of inhibitory factors in the semen.
In simple words: Capacitation is like a warm-up process for sperm cells inside the female body. It makes them active, strong, and ready to swim fast to reach and fertilize the egg.

🎯 Exam Tip: Remember to mention that capacitation takes about 5-6 hours and occurs inside the female reproductive tract, specifically involving changes in the acrosome membrane.

Long Answer Questions

Question 1. Explain the following parts of male reproductive system along with labelled diagram showing these parts – Testis, vasa deferentia, epididymis, seminal vesicle, prostate gland and penis.
OR
With the help of a neat, labelled diagram, describe the human male reproductive system.
Answer:
The human male reproductive system consists of the following main organs:
1. Testis: A pair of oval-shaped primary sex organs located outside the abdominal cavity in a pouch called the scrotum. They produce male gametes (sperms) and secrete the male sex hormone testosterone.
2. Vasa deferentia: A pair of long, muscular tubes that arise from the epididymis and carry mature sperms upward into the abdomen to join the urethra.
3. Epididymis: A highly coiled tube-like structure located on the posterior surface of each testis where sperms are temporarily stored and undergo physiological maturation.
4. Seminal vesicle: A pair of glands that secrete an alkaline, viscous fluid containing fructose, proteins, and prostaglandins, which provides energy and nourishment to the sperms.
5. Prostate gland: A single, chestnut-shaped gland surrounding the urethra that secretes a whitish, alkaline prostatic fluid to neutralize vaginal acidity and enhance sperm motility.
6. Penis: The male copulatory organ that serves to deposit sperms into the female reproductive tract during copulation. The urethra passes through it, serving as a common passage for both urine and semen.
In simple words: The male reproductive system has parts to make sperms (testes), store and mature them (epididymis), carry them (vasa deferentia), add nourishing fluids (seminal vesicles and prostate), and deliver them (penis).

🎯 Exam Tip: When describing these parts, clearly state the specific function of each organ and use bullet points or numbered lists to make your answer easy for the examiner to read.

Male Reproductive System

Diagram Labels:

• Urinary bladder
• Seminal vesicle
• Prostate gland
• Cowper's gland
• Urethra
• Epididymis
• Glans penis
• Prepuce
• Vas deferens
• Testis
• Scrotum
• Gubernaculum

Structure and Components

(i) Testis, the male gonad, the accessory ducts and glands along with external genitalia form the male reproductive system.

(ii) Testes:
1. Testes are male gonads with dimensions of about 4.5 cm length, 2.5 cm width and 3 cm thickness.
2. There are about 200 to 300 lobules in each testis in which there are seminiferous tubules that form rete testis.
3. Testes produce sperms and secrete male sex hormone, androgen or testosterone.

(iii) Accessory ducts: Rete testis, vasa efferentia, epididymis, vas deferens, ejaculatory duct and urethra together form the accessory ducts of male reproductive system.
1. Vasa efferentia: Vasa efferentia are 12-20 fine tubules. They arise from rete testis and end into the epididymis. The sperms from the testis are carried by these ducts to the epididymis.
2. Epididymis: Epididymis are long and coiled tubes having three parts, viz. caput, corpus and cauda epididymis. They are located on the posterior border of each testis. The sperms undergo maturation in epididymis.
3. Vasa deferentia: Vasa deferentia are a pair of 40 cm long tubular structures that arise from cauda epididymis.

🎯 Exam Tip: Remember the pathway of sperm transport: Testis → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra. Memorizing this sequence and the dimensions of the testes will help you score full marks in descriptive questions.

Question 1. Describe the male reproductive system of human (Continued)
Answer:
• Each vas deferens enters the abdominal cavity through the inguinal canal and then ascends in the form of spermatic cord.
• Vas deferens of each side is joined by the duct from seminal vesicle to form ejaculatory duct.

4. Ejaculatory duct: About 2 cm long pair of ducts formed by joining of vas deferens and a duct of seminal vesicle are the ejaculatory ducts. Both ejaculatory ducts open into urethra near the prostate gland. Seminal fluid containing spermatozoa are carried by ejaculatory duct to the urethra.

5. Urethra: The male urethra provides a common passage for the urine and semen hence is also called urinogenital duct.

(iv) Accessory glands: Associated with male reproductive system are: (a) Seminal vesicles (b) Prostate gland and (c) Cowper’s or Bulbourethral glands. Every accessory gland has secretion which helps in functions of reproductive system.

(v) External genitalia: External genitalia consists of penis and scrotum.
1. Penis:
• Penis is the copulatory organ used for insemination or deposition of sperms in female genital tract.
• It is cylindrical, erectile and pendulous organ through which passes the urethra.
• It contains three columns of erectile tissues which has abundant blood sinuses.
• The tip is called glans penis while the retractible fold of skin on penis is called prepuce.

2. Scrotum: The scrotum is a pouch of pigmented skin arising from lower abdominal wall. It protects testes within it. Scrotum acts as thermoregulator. Testis are suspended in scrotum by spermatic cord.
In simple words: The male reproductive system includes ducts like the vas deferens and urethra, accessory glands, and external organs like the penis and scrotum, which work together to produce and deliver sperm.

🎯 Exam Tip: Remember that the urethra in males is called the urinogenital duct because it carries both urine and semen. Clearly label these pathways in diagrams to secure full marks.

Question 2. Describe female reproductive system of human
Answer: The female reproductive system is highly specialized to produce eggs, facilitate fertilization, and support the development of a fetus. It consists of the following components:
1. Ovaries: A pair of primary sex organs that produce ova (eggs) and female sex hormones (estrogen and progesterone).
2. Oviducts (Fallopian Tubes): A pair of tubes that transport the egg from the ovary to the uterus; fertilization typically occurs here.
3. Uterus: A hollow, muscular, pear-shaped organ where the embryo implants and develops during pregnancy.
4. Vagina: A muscular tube that serves as the birth canal and receives sperm during intercourse.
5. External Genitalia (Vulva): Includes the labia majora, labia minora, and clitoris.
6. Accessory Glands: Such as Bartholin's glands, which secrete lubricating fluid.
7. Mammary Glands: Accessory organs essential for newborn nourishment through lactation.
In simple words: The female reproductive system consists of ovaries that make eggs, fallopian tubes where fertilization happens, and a uterus where a baby grows.

🎯 Exam Tip: When describing the female reproductive system, remember to mention both primary organs (ovaries) and accessory structures (like fallopian tubes and uterus) along with their specific functions to score full marks.

Female Reproductive System Diagram Labels

• Fallopian tube
• Ampulla
• Isthmus
• Infundibulum
• Fimbriae
• Ovary
• Ovarian ligament
• Uterus
• Uterine wall
• Endometrium
• Cervix
• Vagina

The female reproductive system consists of internal organs and external genitalia.

Internal organs are pair of ovaries and pair of fallopian ducts or oviducts, single median uterus and vagina. External genitalia is called vulva. There are a pair of vestibular glands in external genitalia. Mammary glands or breasts are also associated with reproductive system of female.

(1) Ovaries

• Ovaries are situated in the abdomen in upper lateral part of the pelvis near the kidneys. Their dimensions are about 3 cm in length, 1.5 cm in breadth and 1.0 cm thick. They are solid, oval or almond shaped organs.
• Ovaries produce ova and they are also endocrine in nature as they produce estrogen, progesterone, relaxin, activin and inhibin.
• Ovarian hormones bring about secondary sexual characters. They also control menstrual cycle, pregnancy and parturition.

(2) Fallopian Tubes / Oviducts

(i) Fallopian tubes lie horizontally over peritoneal cavity. These are about 10 to 12 cm long, narrow, muscular structure lined by ciliated epithelium.
(ii) They transport the ovum after ovulation from the ovary to the uterus.
(iii) Fallopian tube can be subdivided into the following three parts:

• The infundibulum which bears a number of finger-like processes called fimbriae at its free border.
• Infundibulum is funnel-shaped having ostium which receives ova released from the ovary.
• The second part is the ampulla where the fertilization takes place.
• The last part is short cornua or isthmus which opens into the uterus.

(3) Uterus/Womb

(i) Uterus is a pear-shaped, highly muscular, thick walled, hollow organ measuring about 8 cm in length, 5 cm in width and 2 cm in thickness.

(ii) Uterus has the following three parts : Fundus, Body or corpus and Cervix.

(iii) The cervix communicates above with the body of the uterus by an aperture, the internal os and with vagina below by an opening the external os.

(iv) Uterus has three-layered wall. These layers are:

• Perimetrium : An outer serous layer.
• Myometrium : The middle thick muscular layer of smooth muscles.
• Endometrium : The inner highly vascular mucosa that has many uterine glands.

(v) Uterus receives the ovum from fallopian tube. It develops placenta during pregnancy for the nourishment of foetus. At the time of parturition, it expels the young one at birth.

🎯 Exam Tip: Memorize the three layers of the uterine wall (Perimetrium, Myometrium, and Endometrium) and their specific characteristics, as this is a highly important topic for short-answer and diagram-labeling questions.

(4) Vagina

• Vagina is a highly distensible fibro-muscular tube that lies between the cervix and the vestibule.
• It is about 7 to 9 cm in length and is internally lined by stratified and non-keratinised epithelium. The vaginal wall has inner mucous lining.
• Vagina acts as a birth canal as well as copulatory passage. It also allows passage of menstrual flow.
• Vagina opens into vestibule by vaginal orifice which may be covered with hymen which is also a mucous membrane.

(5) External Genitalia or Vulva or Pudendum

The external genitalia consists of five parts; viz. labia majora, labia minora, mons veneris, clitoris and vestibule.

(6) A Pair of Vestibular Glands / Bartholin’s Glands

These glands open into the vestibule and release a lubricating fluid.

🎯 Exam Tip: Be ready to list the five components of the external genitalia and remember that Bartholin's glands are homologous to Cowper's glands in males, secreting a lubricating fluid.

Question 3. Describe the process of fertilization.
Answer:
(1) Fertilization is the process of fusion of the haploid male and female gametes which results in the formation of a diploid zygote \( (2n) \). This crucial biological event marks the beginning of a new unique organism.
(2) In human beings fertilization is internal. Sperms deposited in vagina, swim across the uterus and fertilize the ovum in ampulla of the fallopian tube.
(3) Fertilization involves the following events:
(i) Insemination : Discharge of semen into the vagina at the time of copulation is called insemination.
(ii) Movement of sperm towards egg : Sperms reaching the vagina undergo capacitation process for 5-6 hours. During capacitation acrosomal membrane of sperm becomes thin and \( \text{Ca}^{2+} \) enters the sperm making it extra active. Sperms reach up to the ampulla by swimming aided with contraction of uterus and fallopian tubes. These contractions are stimulated by oxytocin of female. By capacitation sperm can reach ampulla within 5 minutes, they remain viable for 24 to 48 hours, whereas ovum remains viable for 24 hours.
(iii) Entry of sperm into the egg : Though many sperms reach the ampulla, only a single sperm fertilizes the ovum. The acrosome of sperm after coming in contact with the ovum, releases lysins; hyaluronidase and corona penetrating enzymes. Due to these enzymes cells of corona radiata are separated and dissolved. The sperm head then passes through zona pellucida of egg. The zona pellucida has glycoprotein fertilizin receptor proteins. These bind to specific acid protein antifertilizin of sperm. This makes sperm and ovum to come together. Fertilizin-Antifertilizin interaction is species-specific.
(iv) Acrosome reaction : When the sperm head comes in contact with the zona pellucida, its acrosome covering ruptures to release lytic enzymes, acrosin or zona lysin. These enzymes dissolve plasma membrane of egg so that the sperm nucleus and the centrioles enter the egg, while other parts remain outside. Now the secondary oocyte completes its second meiotic division.
In simple words: Fertilization is when a male sperm meets and joins with a female egg to form a single new cell. This cell then starts growing into a baby inside the mother's body.

🎯 Exam Tip: Clearly define the key stages of fertilization like insemination, capacitation, and acrosome reaction using correct biological terms to secure maximum marks.

Question 4. Explain the process by which zygote divides and redivides to form the morula.
Answer:
(1) Cleavage is a rapid mitotic division to form a blastula. These divisions takes place immediately after fertilization. The cells formed by cleavage are called blastomeres.
(2) The type of cleavage in human is holoblastic, i.e. the whole zygote gets divided, radial and indeterminate, i.e. fate of each blastomere is not predetermined.
(3) Cleavage show faster synthesis of DNA and high consumption of oxygen. As these rapid divisions continue, they eventually form a solid ball of 16 to 32 cells known as the morula.
In simple words: After fertilization, the single-celled zygote divides very quickly into multiple smaller cells without growing in size. This rapid division process is called cleavage, which eventually forms a solid ball of cells called a morula.

🎯 Exam Tip: Remember to define 'holoblastic' and 'blastomeres' clearly, as these key terms carry specific marks in description questions about cleavage.

Process of Cleavage in Human Development

(4) Since there is no growth phase between the cleavages, the size of blastomeres will be reduced with every successive cleavage.

Stages of Cleavage:

• A. 2-Cell stage (12-15 hours): Shows polar body and blastomeres.
• B. 4-Cell stage (24-30 hours)
• C. 8-Cell stage
• D. Morula

(5) The cleavages occur as follows:

(6) Successive divisions produce a solid ball of cells called morula of 16 cells. It consists of an outer layer of smaller clearer cells and an inner mass of larger cells.

(7) Morula reaches the uterus about 4-6 days after fertilization.

🎯 Exam Tip: Memorize the exact timeline of each cleavage stage (30, 60, and 72 hours) and note that the overall size of the embryo does not increase during cleavage, only the cell number increases while cell size decreases.