GSEB Class 12 Biology Solutions Chapter 3 Human Reproduction

 

Question 1. Fill in the blanks.
1. Humans reproduce ................... (asexually/sexually)
2. Humans are ................... (oviparous, viviparous, ovoviviparous)
3. Fertilisation is ................... in humans (external/internal)
4. Male and female gametes are ................... (diploid/haploid)
5. Zygote is ................... (diploid/haploid)
6. The process of release of ovum from a mature follicle is called ...................
7. Ovulation is induced by a hormone called ...................
8. The fusion of male and female gametes is called ...................
9. Fertilisation takes place in ...................
10. Zygote divides to form ................... which is implanted in the uterus.
11. The structure which provides a vascular connection between foetus and uterus is ...................
Answer:
1. sexually
2. viviparous
3. internal
4. haploid
5. diploid
6. ovulation
7. LH
8. fertilisation
9. oviduct
10. blastocyst
11. placenta
In simple words: These blanks pertain to fundamental aspects of human reproduction, covering topics from reproductive mode and gamete ploidy to specific processes like ovulation and the structures involved in development.

🎯 Exam Tip: Understanding these basic terms and processes is crucial for building a strong foundation in human reproduction and often features in multiple-choice or short-answer questions.

 

Question 2. Draw a labelled diagram of male reproductive system.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव पुरुष प्रजनन प्रणाली के विभिन्न अंगों को दर्शाता है। इसमें शुक्राणु नलिका (वास डिफरेंस), मूत्रवाहिनी, मूत्राशय, सेमिनल वेसिकल्स, प्रोस्टेट ग्रंथि, मलाशय, गुदा, रक्त साइनस, मूत्रमार्ग, शिश्न मुंड, काउपर ग्रंथि, एपिडिडिमिस, वृषण, प्रिप्यूस (अग्रत्वचा), अंडकोष और श्रोणि की हड्डी जैसे प्रमुख भाग शामिल हैं। यह चित्र इन अंगों की शारीरिक स्थिति और उनके बीच के संबंधों को स्पष्ट करता है।
In simple words: The male reproductive system diagram illustrates organs like testes, epididymis, vas deferens, seminal vesicle, prostate gland, and urethra, all essential for sperm production and delivery.

🎯 Exam Tip: When drawing diagrams, ensure all key structures are clearly labeled and proportionate. Accuracy in labeling is often more important than artistic skill.

 

Question. Draw a labelled diagram of female reproductive system.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव मादा प्रजनन प्रणाली के अंगों को दर्शाता है, जिसमें गर्भाशय, डिंबवाहिनी, अंडाशय, योनि और सहायक संरचनाएं शामिल हैं। चित्र में गर्भाशय (यूट्रस), मूत्राशय, भगशेफ (क्लिटोरिस), मूत्रमार्ग (यूरेथ्रा), डिंबवाहिनी (ओविडक्ट), एम्पुला, इस्थमस, गर्भाशय फंडस, इन्फंडिबुलम, एंडोमेट्रियम, मायोमेट्रियम, पेरिमेट्रियम, गर्भाशय ग्रीवा (सर्विक्स), गुदा और योनि जैसे प्रमुख भागों को दर्शाया गया है। यह संरचनाओं की शारीरिक स्थिति को एक पार्श्व दृश्य और सामने के दृश्य से स्पष्ट करता है।
In simple words: The female reproductive system diagram shows organs like the ovaries, fallopian tubes (oviducts), uterus, cervix, and vagina, which are crucial for egg production, fertilization, and gestation.

🎯 Exam Tip: For reproductive system diagrams, focus on the interconnectedness of organs and their roles. Clearly distinguishing between internal and external structures is also beneficial.

 

Question 4. Write two major functions each of testis and ovary.
Answer:
**Testis:**
• वृषण शुक्राणुओं का निर्माण करते हैं।
• ये टेस्टोस्टेरोन हार्मोन का स्राव करते हैं।
**Ovary:**
• अंडाशय अंडों (ओवा) का निर्माण करते हैं।
• ये एस्ट्रोजन और प्रोजेस्टेरोन हार्मोन का स्राव करते हैं।
In simple words: Testes produce sperm and testosterone, while ovaries produce eggs and female hormones like estrogen and progesterone.

🎯 Exam Tip: Remember to list distinct functions for each organ. For endocrine organs, mentioning both gamete production and hormone secretion is key.

 

Question 5. Describe the structure of a seminiferous tubule.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र वृषण की सेमिनिफेरस नलिका के एक छोटे हिस्से का अनुप्रस्थ काट दर्शाता है, जिसमें शुक्राणुजनन की प्रक्रिया दिखाई गई है। इसमें प्राथमिक शुक्राणुकोशिकाएं, सर्टोली कोशिकाएं, बेसल झिल्ली, द्वितीयक शुक्राणुकोशिकाएं, शुक्राणुजन और परिपक्व शुक्राणु शामिल हैं। सर्टोली कोशिकाएं विकासशील शुक्राणुओं को पोषण प्रदान करती हैं, जबकि शुक्राणुजनन की विभिन्न अवस्थाएं नलिका की दीवार के भीतर दिखाई गई हैं।
In simple words: Seminiferous tubules are found in the testes and are lined by germinal epithelial cells that undergo spermatogenesis, with Sertoli cells providing support and nourishment to developing sperm.

🎯 Exam Tip: When asked to describe a structure, including its cellular components and their arrangement, along with a textual description of the image, demonstrates comprehensive understanding.

 

Question 6. What is spermatogenesis? Briefly describe the process of spermatogenesis.
Answer: शुक्राणुजनन वह प्रक्रिया है जिसमें शुक्राणुओं का निर्माण होता है। इसमें शुक्राणुजनन कोशिकाएं (spermatids) और शुक्राणु रूपांतरण (spermiogenesis) शामिल हैं। शुक्राणुजनन अपरिपक्व नर जनन कोशिकाओं से शुक्राणुओं के उत्पादन की क्रिया है। यह यौवनारंभ में शुरू होती है और आमतौर पर मृत्यु तक निर्बाध रूप से जारी रहती है, हालांकि बढ़ती उम्र के साथ शुक्राणुओं की संख्या में थोड़ी कमी देखी जाती है।
**शुक्राणुजनन की प्रक्रिया:**
सेमिनिफेरस नलिकाओं के भीतरी भाग में उपस्थित शुक्राणुजन (spermatogonia) (2N) समसूत्री विभाजनों द्वारा संख्या में वृद्धि करते हैं। ये कोशिकाएं समसूत्री विभाजन बंद कर देती हैं, बढ़ती हैं और प्राथमिक शुक्राणुकोशिकाएं (2N) बन जाती हैं। प्रत्येक प्राथमिक शुक्राणुकोशिका अर्धसूत्रीविभाजन से गुजरकर दो समान अगुणित द्वितीयक शुक्राणुकोशिकाएं (N) बनाती है। प्रत्येक द्वितीयक शुक्राणुकोशिका फिर दूसरे अर्धसूत्रीविभाजन से गुजरकर चार समान अगुणित कोशिकाएं बनाती है जिन्हें शुक्राणुजन (spermatids) (N) कहा जाता है। शुक्राणुजन को शुक्राणु रूपांतरण (spermiogenesis) की प्रक्रिया द्वारा शुक्राणु बनाने के लिए पोषण प्राप्त होता है।
In simple words: Spermatogenesis is the biological process of sperm formation from germ cells in the testes, involving mitotic and meiotic divisions followed by spermiogenesis, where spermatids mature into functional spermatozoa.

🎯 Exam Tip: Clearly distinguish between the overall process of spermatogenesis and its sub-stages, like spermiogenesis. Mentioning the ploidy level (2N or N) at each stage is crucial for full marks.

 

Question 7. Name the hormones involved in regulation of spermatogenesis.
Answer: शुक्राणुजनन के नियमन में शामिल हार्मोन हैं: GnRH (हाइपोथैलेमस से), ICSH और FSH (पीयूष ग्रंथि से), तथा एण्ड्रोस्टेरोन और टेस्टोस्टेरोन (वृषण से)।
In simple words: Spermatogenesis is regulated by hormones from the hypothalamus (GnRH), pituitary (ICSH, FSH), and testes (androsterone, testosterone).

🎯 Exam Tip: It's important to know the source gland for each hormone when listing them, as this demonstrates a deeper understanding of endocrine control.

 

Question 8. Define spermiogenesis and spermiation.
Answer:
• **शुक्राणु रूपांतरण (Spermiogenesis):** यह अगुणित शुक्राणुजन (spermatid) (n) से शुक्राणु (spermatozoa) (n) के विकास और विभेदीकरण की प्रक्रिया है।
• **शुक्राणुमोचन (Spermiation):** परिपक्व शुक्राणुओं का सर्टोली कोशिकाओं से अलग होना शुक्राणुमोचन कहलाता है।
In simple words: Spermiogenesis is the maturation of spermatids into spermatozoa, while spermiation is the release of these mature spermatozoa from Sertoli cells.

🎯 Exam Tip: Pay attention to the subtle differences between these two terms; they represent sequential steps in sperm development and release, respectively.

 

Question 9. Draw a labelled diagram of sperm.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक परिपक्व मानव शुक्राणु की संरचना को दर्शाता है, जिसे आमतौर पर सिर, मध्य खंड और पूंछ में विभाजित किया जाता है। सिर में एक एक्रोसोम और नाभिक होता है, मध्य खंड में माइटोकॉन्ड्रिया ऊर्जा प्रदान करते हैं, और पूंछ गतिशीलता के लिए जिम्मेदार होती है।
In simple words: A sperm diagram typically shows a head (containing genetic material and acrosome), a middle piece (with mitochondria for energy), and a tail (for movement).

🎯 Exam Tip: Focus on accurately labeling the main regions (head, middle piece, tail) and key structures within them like the acrosome, nucleus, and mitochondria.

 

Question 10. What are the major components of seminal plasma?
Answer: शुक्राणु प्लाज्मा के प्रमुख घटक फ्रुक्टोज, फाइब्रिनोजेन, प्रोफाइब्रिनोलाइसिन, कैल्शियम बाइकार्बोनेट, प्रोस्टाग्लैंडिन और बलगम हैं।
In simple words: Seminal plasma contains fructose for energy, fibrinogen, profibrinolysin, calcium bicarbonate, prostaglandins, and mucus, all crucial for sperm survival and movement.

🎯 Exam Tip: Listing these components accurately, possibly mentioning their basic function, demonstrates a good grasp of male reproductive physiology.

 

Question 11. What are the major functions of male accessory ducts and glands?
Answer: नर सहायक नलिकाएं जैसे वासा एफरेंशिया, एपिडिडिमिस और वास डिफरेंस शुक्राणुओं के लिए मार्ग प्रदान करते हैं। प्रोस्टेट ग्रंथि का स्राव शुक्राणुओं की गति को सक्रिय करता है। सेमिनल वेसिकल का स्राव शुक्राणुओं की गति के लिए ऊर्जा प्रदान करता है। इसके अलावा, सहायक ग्रंथियों का स्राव परिवहन के लिए एक तरल माध्यम, पोषक तत्व प्रदान करता है, और गर्भाशय की अम्लता का प्रतिकार करने के लिए एक क्षारीय माध्यम भी प्रदान करता है।
In simple words: Male accessory ducts transport sperm, while accessory glands provide seminal fluid rich in nutrients, enzymes, and buffers, activating sperm motility and counteracting vaginal acidity.

🎯 Exam Tip: When describing functions, try to group them by the type of structure (ducts for transport, glands for secretions) and highlight the benefit each provides to sperm viability and function.

 

Question 12. What is oogenesis? Give a brief account of oogenesis.
Answer: अंडाणु के निर्माण और परिपक्वता की प्रक्रिया को अंडाणुजनन (oogenesis) कहते हैं।
अंडाणुजनन की प्रक्रिया ग्राफिक पुटिकाओं में होती है। मादा भ्रूण में अंडाशय में 400,000 तक पुटिकाएं हो सकती हैं। एक महिला सामान्यतः लगभग 30 वर्षों तक प्रति वर्ष 13 बार ओवुलेट करती है, इस प्रकार प्रजनन अवधि (यौवनारंभ से रजोनिवृत्ति तक) के दौरान लगभग 400 अंडे परिपक्व होकर निकलते हैं।
अंडाणुजनन की प्रक्रिया स्तनधारी के जन्म से पहले ही शुरू हो जाती है। नवजात मानव मादा में सभी जनन कोशिकाएं प्राथमिक अंडाणु (primary oocytes) की अवस्था में होती हैं। यौवनारंभ के बाद ही प्राथमिक अंडाणु पहले अर्धसूत्रीविभाजन की अवस्था में प्रवेश करता है। इस प्रकार, अंडाणुजनन एक असंतुलित प्रक्रिया है। शुक्राणुजनन की तरह, अंडाणुजनन भी तीन चरणों में पूरा होता है, जो इस प्रकार हैं:
(i) **गुणा चरण (Multiplication phase):** इस चरण के दौरान, आदिम जनन कोशिकाएं (जनन उपकला कोशिकाएं) बार-बार समसूत्री विभाजन से गुजरकर अंडे की मातृ कोशिकाएं या ऊगोनिया (oogonia) बनाती हैं। ये कोशिकाएं प्रकृति में द्विगुणित होती हैं।
(ii) **वृद्धि चरण (Growth phase):** इस चरण में, कुछ ऊगोनिया समसूत्री विभाजन बंद कर देते हैं और अंडे की जर्दी के रूप में पोषक तत्वों को जमा करके आकार में बढ़ते हैं। अब इन कोशिकाओं को प्राथमिक अंडाणु कहा जाता है। ये कोशिकाएं भी प्रकृति में द्विगुणित होती हैं। अंडाणुजनन में शुक्राणुजनन की तुलना में वृद्धि की बड़ी भूमिका होती है। विकासशील प्राथमिक अंडाणु को उसके चारों ओर पाई जाने वाली पुटिका कोशिकाओं द्वारा पोषण मिलता है। पुटिका कोशिकाएं संशोधित ऊगोनिया होती हैं।
(iii) **परिपक्वता चरण (Maturation phase):** इस चरण के दौरान, प्राथमिक अंडाणु दो विभाजनों से गुजरता है। पहले अर्धसूत्री विभाजन (न्यूनीकरण विभाजन) के परिणामस्वरूप दो असमान अगुणित कोशिकाएं बनती हैं। बड़ी कोशिका को द्वितीयक अंडाणु और छोटी कोशिका को ध्रुवीय पिंड (या पोलोसाइट) के रूप में जाना जाता है। ध्रुवीय पिंड द्वितीयक अंडाणु के एनिमल पोल से जुड़ा होता है। द्वितीयक अंडाणु दूसरा अर्धसूत्री विभाजन (दूसरा अर्धसूत्री विभाजन केवल निषेचन के बाद होता है) से गुजरता है और दो असमान कोशिकाएं बनाता है। बड़ी कोशिका को कार्यात्मक अंडाणु या ऊटिड और छोटी कोशिका को द्वितीयक ध्रुवीय पिंड कहा जाता है। इस समय पहला ध्रुवीय पिंड दो में विभाजित हो जाता है। इस प्रकार अंडाणुजनन के दौरान एक द्विगुणित ऊगोनियम एक अगुणित अंडाणु और तीन ध्रुवीय पिंड देता है। बाद वाले अंततः पतित हो जाते हैं।
In simple words: Oogenesis is the process of egg formation and maturation in the ovaries, starting before birth and pausing until puberty. It involves multiplication, growth, and maturation phases, ultimately yielding one functional ovum and three polar bodies from a diploid oogonium.

🎯 Exam Tip: For oogenesis, emphasize its discontinuous nature and the unequal cytoplasmic division leading to one large ovum and smaller polar bodies, contrasting it with spermatogenesis.

 

Question 13. Draw a labelled diagram of a section through ovary.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक अंडाशय के अनुप्रस्थ काट को दर्शाता है, जिसमें जर्मिनल एपिथेलियम, कॉर्टेक्स और मज्जा जैसे मुख्य भाग दिखाई देते हैं। इसमें विकासशील पुटिकाएं (ग्रोइंग फॉलिकल), परिपक्व पुटिकाएं (मैचुरिंग फॉलिकल), कॉर्पस ल्यूटियम, कॉर्पस अल्बिकन्स, ओवम और ruptured फॉलिकल की विभिन्न अवस्थाओं को भी स्पष्ट रूप से लेबल किया गया है, जो अंडाणुजनन के चरणों को प्रदर्शित करता है।
In simple words: The diagram of an ovary section displays various stages of follicular development, from growing follicles to a mature follicle, ovulation, corpus luteum formation, and eventually corpus albicans.

🎯 Exam Tip: When illustrating the ovary, it's crucial to show the progression of follicles from primordial to mature Graafian follicles, and the formation of the corpus luteum and albicans after ovulation.

 

Question 14. Draw a labelled diagram of a Graafian follicle.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक अंडाणु की संरचना को दर्शाता है, जैसा कि एक परिपक्व ग्राफिक पुटिका के भीतर पाया जाता है। इसमें अंडाणु का नाभिक, कोशिका द्रव्य, ध्रुवीय पिंड, विटेललाइन झिल्ली, ज़ोना पेलुसिडा, प्लाज्मा झिल्ली और ग्राफिक पुटिका कोशिकाएं शामिल हैं। यह अंडाणु और उसे घेरने वाली सुरक्षात्मक परतों का विवरण प्रदान करता है, जो निषेचन के लिए महत्वपूर्ण हैं।
In simple words: The diagram displays the structure of an ovum, including its nucleus, cytoplasm, polar body, vitelline membrane, zona pellucida, plasma membrane, and the surrounding Graafian follicles, indicating its maturity for fertilization.

🎯 Exam Tip: For a Graafian follicle or ovum diagram, correctly label the layers surrounding the ovum (zona pellucida, corona radiata if applicable), the polar body, and the nucleus, as these are critical for understanding fertilization.

 

Question 14.
Inhibits GnRH and
LH production

ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख शुक्राणुजनन के हार्मोनल नियंत्रण को दर्शाता है। यह हाइपोथैलेमस से GnRH, पिट्यूटरी से LH और FSH, तथा वृषण से टेस्टोस्टेरोन और इनहिबिन जैसे विभिन्न हार्मोन की परस्पर क्रिया को दिखाता है, जो शुक्राणु उत्पादन और प्रजनन अंगों के कार्यों को नियंत्रित करते हैं। यह पुरुष प्रजनन प्रणाली में हार्मोनल नियमन के जटिल मार्ग को चित्रित करता है।
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख अंडाजनन के हार्मोनल नियंत्रण को दर्शाता है। हाइपोथैलेमस से GnRH, पिट्यूटरी से LH और FSH, तथा अंडाशय से एस्ट्रोजन और प्रोजेस्टेरोन जैसे हार्मोन की परस्पर क्रिया को दिखाता है। यह हार्मोनल फीडबैक लूप (सकारात्मक और नकारात्मक) को भी चित्रित करता है जो डिंब के उत्पादन और गर्भाशय के कार्य को नियंत्रित करते हैं।
In simple words: The hormonal regulation of oogenesis involves a feedback loop where GnRH from the hypothalamus stimulates the pituitary to release FSH and LH, which in turn act on the ovary to produce estrogen and progesterone, thereby controlling egg development and uterine changes.

🎯 Exam Tip: Understanding the hormonal feedback mechanisms is crucial; focus on the source of each hormone and its target organ/function for higher scores.

 

Question 15.
Explain the terms. Vasectomy, Hysterectomy and Tubectomy.

Answer:
• **Vasectomy:** This surgical procedure involves male sterilization, achieved by cutting and ligating the vas deferens tubes in males.
• **Hysterectomy:** This operation entails the surgical removal of the uterus and the cervix.
• **Tubectomy:** This method of female sterilization is performed by cutting and tying the fallopian tubes.

In simple words: Vasectomy is male sterilization, tubectomy is female sterilization (both involve cutting and tying reproductive ducts), and hysterectomy is the surgical removal of the uterus and cervix.

🎯 Exam Tip: Clearly differentiate between these three procedures, noting the gender and specific organs involved, as they are distinct medical interventions.

 

Question 16.
The diagram below shows the formation of sperm. Like this draw a diagram showing the formation of ovum with suitable labels.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख शुक्राणुजनन की प्रक्रिया को दर्शाता है, जिसमें शुक्राणुगोनिम से लेकर परिपक्व शुक्राणु तक के विभिन्न चरण शामिल हैं: गुणन चरण, वृद्धि चरण, अर्धसूत्रीविभाजन चरण और शुक्राणुजनन। यह दिखाता है कि शुक्राणुगोनिम (Spermatogonium) कैसे प्राथमिक शुक्राणुकोशिका, द्वितीयक शुक्राणुकोशिका, शुक्राणुद (Spermatid) और अंततः शुक्राणु में परिवर्तित होता है।
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख अंडाणुजनन की प्रक्रिया को दर्शाता है, जिसमें अंडाणुगोनिम से लेकर परिपक्व अंडाणु तक के विभिन्न चरण शामिल हैं। इसमें गुणन चरण, वृद्धि चरण और अर्धसूत्रीविभाजन चरण शामिल हैं, जिससे प्राथमिक डिंबग्रंथि, द्वितीयक डिंबग्रंथि, ध्रुवीय पिंड और अंततः एक परिपक्व अंडाणु बनता है। यह प्रक्रिया भ्रूण अवस्था में शुरू होती है और यौवनारंभ के बाद जारी रहती है।
In simple words: Oogenesis is the process of egg formation in females, starting from oogonium, progressing through oocyte stages and meiotic divisions, eventually producing one functional ovum and polar bodies.

🎯 Exam Tip: When asked to draw biological diagrams, ensure all key structures are accurately represented and clearly labeled, as precise labeling often carries significant marks.

 

Question 17.
Normally polyspermy does not occur.
a. What happens if it occurs?
b. Which structure prevents polyspermy in ovum?

Answer:
a. If polyspermy takes place, the development of the zygote will not proceed normally.
b. The fertilization membrane is the structure that prevents polyspermy in the ovum.

In simple words: If multiple sperms fertilize an egg (polyspermy), normal development fails; a fertilization membrane forms to block additional sperm entry.

🎯 Exam Tip: Remember the fertilization membrane's critical role in preventing polyspermy; its formation is a key post-fertilization event.

 

Question 18.
Mention the difference between breech birth and normal birth.

Answer:
In a breech birth, the fetus emerges buttocks-first, whereas in a normal birth, the fetus presents head-first.

In simple words: Breech birth is when the baby comes out feet or bottom first, while normal birth is head first.

🎯 Exam Tip: Focus on the fetal presentation (head-first vs. buttocks/feet-first) as the primary distinguishing factor between normal and breech births.

 

Question 19.
some parts of the embryo differentiate into a set of membranes called the extraembryonic membrane.
a. Name the extraembryonic membrane.
b. Mention its importance in embryonic development.

Answer:
a. The extraembryonic membranes include the amnion, chorion, allantois, and yolk sac.
b. All these membranes collectively contribute to the support and development of the embryo.

In simple words: Extraembryonic membranes are structures like the amnion, chorion, allantois, and yolk sac that support and protect the developing embryo.

🎯 Exam Tip: List all four extraembryonic membranes and briefly state their collective role in fetal support and protection for a complete answer.

 

Question 20.
Generally the delivery room is described as labour room. Why?

Answer:
Delivery rooms are commonly referred to as "labor rooms" because the term "labor" describes the intense muscular contractions that expel the fetus through the vagina during childbirth.

In simple words: Delivery rooms are called labor rooms because childbirth involves strong muscular contractions, which is "labor."

🎯 Exam Tip: Connect the term "labor" directly to the muscular contractions and effort involved in childbirth for a concise explanation.

 

Question 21.
In a breech birth, the baby is taken out by making an incision in the mother's abdomen. The method is called 'caesarean' not 'scissorian'. Why is it called so?

Answer:
The procedure is named "Caesarean section" due to the belief that Julius Caesar himself was born through this method, giving rise to the historical nomenclature.

In simple words: The surgical removal of a baby from the abdomen is called a Caesarean section because of the legend that Julius Caesar was born this way.

🎯 Exam Tip: Mention the historical belief associated with Julius Caesar as the origin of the term "Caesarean" to answer this question accurately.

 

Question 22.
The following figure shows the safety periods and fertile period of a normal lady.
In this lady menses occurs on first day.
a. What is fertile period?
b. What is safety period?

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक सामान्य महिला के मासिक धर्म चक्र को दर्शाता है, जिसमें मासिक धर्म (1-5 दिन), प्रजनन काल (6-19 दिन), और सुरक्षित काल (20-28 दिन) की पहचान की गई है। इसमें ओव्यूलेशन के दिन (लगभग 14वें दिन) को भी दर्शाया गया है, जो प्रजनन क्षमता के शिखर को इंगित करता है, और चक्र के अंत में अगला मासिक धर्म शुरू होने से पहले सुरक्षित दिनों का संकेत देता है।
Answer:
a. The fertile period is the time during which fertilization is most likely to occur.
b. The safety period is the time when fertilization is unlikely to happen.
c. The day of ovulation is when the ovum is released.

In simple words: The fertile period is when pregnancy is possible, the safety period is when it's unlikely, and ovulation is the day the egg is released.

🎯 Exam Tip: Accurately identify the fertile period as the window for potential conception and the safety period as the time when conception is less probable, based on the menstrual cycle. The day of ovulation is the most fertile day.

 

Question 23.
In mammals, the testes are placed in the scrotal sacs. Give reason.

Answer:
The testes are located in the scrotal sacs in mammals because these sacs maintain an optimal temperature (typically 32-35°C) that is lower than the body temperature (37°C), which is essential for proper spermatogenesis (sperm formation).

In simple words: Testes are in the scrotum to keep them cooler than body temperature, which is necessary for healthy sperm production.

🎯 Exam Tip: The key reason is temperature regulation; always link the scrotal location to providing a lower temperature suitable for spermatogenesis.

 

Question 24.
Siamese twins are always either male or female and never be male and female.
a. Why are the twins called Siamese twins?
b. What do you mean by identical twins?
c. What are fraternal twins?

Answer:
a. These twins are known as Siamese twins because the first documented case was reported in Siam (now Thailand).
b. Identical twins develop from a single zygote and are always of the same sex (either all male or all female).
c. Fraternal twins originate from two distinct zygotes and can therefore be of different sexes.

In simple words: Siamese twins got their name from the first reported case; identical twins come from one egg and are always the same sex, while fraternal twins come from two separate eggs and can be different sexes.

🎯 Exam Tip: Distinguish clearly between identical (monozygotic) and fraternal (dizygotic) twins by their zygotic origin and sex characteristics. For Siamese twins, remember the historical naming context.

 

Question 25.
Placenta makes the intimacy between mother and foetus.
a. What is placenta?
b. In what way it makes intimacy with foetus?
c. Name the portions of foetal and maternal parts of placenta.

Answer:
a. The placenta serves as the physiological connection between the mother and the developing fetus.
b. It fosters intimacy by facilitating the transfer of nourishment and growth factors from the mother to the embryo, and concurrently, removing waste products from the fetus. This bidirectional exchange strengthens the bond and dependency.
c. The fetal portion of the placenta is the chorionic villi, while the maternal portion is the decidua basalis.

In simple words: The placenta is the essential link between mother and fetus, providing nutrients and removing waste, thus creating a close connection; it consists of both fetal (chorionic villi) and maternal (decidua basalis) parts.

🎯 Exam Tip: Remember the placenta's dual role in nutrient supply and waste removal, and specifically identify the chorionic villi (fetal) and decidua basalis (maternal) as its key components.

 

Question 26.
Copy the diagram. Identify and label any five parts.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक परिपक्व मानव शुक्राणु की संरचना को दर्शाता है, जिसमें सिर, गर्दन, मध्य-खंड और पूंछ जैसे मुख्य भाग शामिल हैं। सिर में एक्रोसोम और नाभिक होता है, मध्य-खंड में माइटोकॉन्ड्रियल सर्पिल ऊर्जा के लिए होता है, और पूंछ गतिशीलता प्रदान करती है। यह शुक्राणु के विभिन्न कार्यात्मक क्षेत्रों को उजागर करता है।
Answer:The structure of a sperm is composed of a head, neck, a middle piece, and a tail. The entire sperm body is enveloped by a plasma membrane. The anterior region of the head is covered by a cap-like structure called the acrosome, which contains enzymes crucial for ovum fertilization. The middle piece is rich in mitochondria, generating the energy required for the tail's movement, which is essential for sperm motility during fertilization.

In simple words: A sperm has a head (with acrosome and nucleus), a neck, a middle piece (for energy), and a tail (for movement), all covered by a plasma membrane, to facilitate fertilization.

🎯 Exam Tip: When describing sperm structure, highlight the acrosome's role in fertilization and the mitochondria's function in providing energy for motility; these are frequently tested points.

 

Question 27.
Name the accessory glands of human male reproductive system and mention their functions.

Answer:
The accessory glands of the human male reproductive system include:
1. **A pair of seminal vesicles:** These glands secrete seminal plasma, a fluid rich in calcium, fructose, and various enzymes.
2. **A prostate gland:** The seminal plasma produced by this gland provides a fluid medium, aiding sperm movement through the female reproductive tract towards the ovum.
3. **A pair of bulbourethral glands:** These glands contribute secretions that provide nourishment to the sperm and also assist in lubricating the penis.

In simple words: Male accessory glands – seminal vesicles, prostate, and bulbourethral glands – produce seminal plasma, which nourishes sperm, provides a fluid medium for movement, and lubricates the reproductive tract.

🎯 Exam Tip: For each accessory gland, clearly state its name and a primary function related to seminal plasma composition, sperm nourishment, or lubrication, as these are key aspects.

 

Question 28.
Find out the correct sequence from below.
a. Fertilisation \( \to \) zygote \( \to \) blastula \( \to \) morula cleavage \( \to \) gastrula
b. Cleavage \( \to \) zygote fertilization \( \to \) morula \( \to \) blastula \( \to \) gastrula
c. Fertilisation \( \to \) cleavage \( \to \) morula \( \to \) zygote \( \to \) blastula \( \to \) gastrula
d. Fertilisation \( \to \) zygote \( \to \) cleavage \( \to \) morula \( \to \) blastula \( \to \) gastrula
e. Zygote \( \to \) fertilisation \( \to \) gastrula \( \to \) cleavage \( \to \) morula.

Answer: (d) Fertilisation \( \to \) zygote \( \to \) cleavage \( \to \) morula \( \to \) blastula \( \to \) gastrula

In simple words: The correct order of early embryonic development starts with fertilization, forming a zygote, which then undergoes cleavage to become a morula, then a blastula, and finally a gastrula.

🎯 Exam Tip: Memorize the precise sequence of early embryonic stages: fertilization, zygote, cleavage, morula, blastula, and gastrula, as questions on this order are common.

 

Question 29.
The ovum is surrounded by four membranes. How can a sperm enter and fuse with the female pronuclei?

Answer:
Sperm overcome the ovum's surrounding membranes by releasing specific enzymes such as antifertilizin and lysin (spermlysin), which help break down these protective layers, enabling the sperm to reach and fuse with the female pronucleus.

In simple words: Sperm use enzymes like antifertilizin and spermlysin to break through the egg's protective layers and fuse with the female nucleus.

🎯 Exam Tip: Focus on the role of specific enzymes (e.g., lysin/spermlysin, hyaluronidase from the acrosome) produced by the sperm that facilitate penetration of the egg membranes.

 

Question 30.
Observe the diagrams and answer the questions that follow.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव प्रजनन में दो प्रक्रियाओं, शुक्राणुजनन (A) और अंडाणुजनन (B) को दर्शाता है। आरेख A शुक्राणु कोशिकाओं के क्रमिक विकास को प्रदर्शित करता है, जबकि आरेख B अंडाणु कोशिकाओं के विकास को दिखाता है, जिसमें अर्धसूत्रीविभाजन और ध्रुवीय पिंडों का निर्माण शामिल है। ये दोनों आरेख युग्मकजनन के आवश्यक चरणों को स्पष्ट करते हैं।
Answer:
a. Process A represents Spermatogenesis, and Process B represents Oogenesis.
b. The three phases involved in these events are the Multiplication phase, Growth phase, and Maturation phase.
c. The differences between Spermatogenesis and Oogenesis are detailed in the table below:

Spermatogenesis	Oogenesis
i. It occurs in the testis.	i. It occurs in the ovary.
ii. Gamete is called sperm.	ii. Gamete is called ovum.
iii. Only a limited growth occurs during growth phase.	iii. Very elaborate growth phase.
iv. Each primary spermatocyte gives 4 functional sperms.	iv. Each primary oocyte gives only one functional ovum and three polar bodies.
v. It begins at puberty and extends upto senility.	v. It begins at embryonic stage and sus- pended midway at the time of birth. The remaining part takes place only after puberty.

In simple words: Spermatogenesis (sperm formation) happens in testes, producing four sperms continuously from puberty. Oogenesis (egg formation) happens in ovaries, producing one ovum and polar bodies, starting in the embryonic stage and resuming at puberty.

🎯 Exam Tip: When comparing spermatogenesis and oogenesis, highlight the site of occurrence, the number of functional gametes produced, and the timing of initiation and completion for full marks.

 

Question 31.
During cleavage of the mammalian zygote, the resultant blastomeres become smaller and smaller. Comment on this statement.

Answer:
Cleavage refers to the repeated cell divisions of a fertilized egg, leading to a group of smaller cells known as blastomeres. The initial cleavage is vertical, producing two unequal cells, while the second is perpendicular, resulting in four cells. Subsequent divisions are rapid, forming a solid mass of cells resembling a mulberry, called a morula. The blastomeres diminish in size because, during this phase, each cell is acquiring the developmental instructions to differentiate into specific organs later. This division of labor during organogenesis ensures that these cells form distinct organs through differentiation.

In simple words: During early embryonic cleavage, cells divide rapidly without growing, making them smaller. This happens because these cells are essentially getting ready to specialize and form different body parts later.

🎯 Exam Tip: The key concept here is that cleavage involves cell division without growth, and the decreasing cell size is linked to the "division of labor" and subsequent differentiation for organogenesis.

 

Question 32.
A human ovum is released on the 14th day of menstrual cycle.
a. What happens to the ovum if it is fertilised by a sperm?
b. Where does the fertilisation occur?
c. What will happen to the Graafian follicles if the ovum is fertilised?

Answer:
a. If an ovum is fertilized by a sperm, it transforms into a zygote.
b. Fertilization typically occurs in the ampullary-isthmic junction of the fallopian tube.
c. If the ovum is fertilized, the remaining Graafian follicle transforms into the corpus luteum, which then secretes progesterone to maintain the pregnancy.

In simple words: If fertilized, an ovum becomes a zygote in the fallopian tube; the Graafian follicle transforms into a corpus luteum, producing progesterone for pregnancy.

🎯 Exam Tip: Remember that fertilization forms a zygote, occurs in the fallopian tube, and leads to the Graafian follicle becoming the progesterone-secreting corpus luteum to support early pregnancy.

 

Question 33.
What is Oogenesis? Give a brief account of Oogenesis.

Answer:
Oogenesis is the biological process of forming and maturing female gametes, or ova. This process initiates in the embryonic stage, where primordial germ cells in the fetal ovary undergo mitotic divisions to produce oogonia. These oogonia then enter a growth phase, transforming into primary oocytes, which become arrested in Prophase I of meiosis. Each primary oocyte is enveloped by a layer of granulosa cells, forming a primary follicle. As more granulosa cell layers accumulate, it develops into a secondary follicle, then a tertiary follicle, characterized by a fluid-filled antrum. The primary oocyte within the tertiary follicle completes Meiosis I, yielding a larger haploid secondary oocyte and a smaller polar body. The secondary oocyte then ruptures from the mature Graafian follicle and moves into the fallopian tube. Meiosis II in the secondary oocyte completes only upon sperm entry, resulting in a functional ovum (ootid) and a second polar body. Consequently, one diploid oogonium ultimately produces one haploid ovum and three polar bodies, which eventually degenerate.

In simple words: Oogenesis is the process where female gametes (ova) are formed and mature, beginning in the embryonic stage and continuing until after fertilization, producing one functional ovum and polar bodies.

🎯 Exam Tip: Focus on the stages (multiplication, growth, maturation), the timing (embryonic initiation, arrest, puberty completion), and the products (one ovum, three polar bodies) for a comprehensive answer on oogenesis.

 

Question 34.
The germ layers are given. Complete the organs derived from the germ layers. Copy and complete the table.

Answer:

Germ layers	Derived organs
Ectoderm	Central nervous system, sense organs, adrenal medulla, buccal cavity, pituitary, skin, nail, hoof, hair, feather.
Mesoderm	Skeleton, muscles, circulatory system, excretory system, adrenal reproductive system, dermis of skin.
Endoderm	Digestive tract, respiratory system, liver, pancreas, urinary bladder, thymus, thyroid, middle ear cavity, lining of vagina, associated reproductive glands.

In simple words: Ectoderm forms nervous system, skin; mesoderm forms muscles, bones, circulatory system; endoderm forms digestive, respiratory linings, and glands.

🎯 Exam Tip: Clearly categorize derivatives for each germ layer (ectoderm, mesoderm, endoderm) as this demonstrates understanding of embryonic development and organ formation.

 

Question 35.
A woman has conceived and implantation occurred within her uterus. Discuss the sequence of changes upto the parturition which will take place within her body under the influence of various hormones.

Answer:
After implantation, the trophoblast develops finger-like projections called chorionic villi, which become interdigitated with uterine tissue and maternal blood, forming the complex structure known as the placenta. The placenta functions as a structural and functional bridge between the developing embryo and the mother. **Functions of the Placenta:** * It acts as a barrier, regulating exchange between the fetus and the mother. * It serves as an ultrafilter. * It permits the passage of soluble inorganic and organic materials, nutrients, hormones, and antibodies (e.g., against diphtheria, smallpox, scarlet fever, measles) from the mother to the fetus. * It facilitates the exchange of gases between the mother and the fetus. * It aids in the elimination of nitrogenous waste products and other fetal waste. * It acts as an endocrine gland, producing hormones such as human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, and progestogens. At parturition, the placenta also secretes relaxin, which helps relax pubic ligaments, aiding in childbirth. Immediately post-implantation, the inner cell mass (embryo) differentiates into three primary germ layers: the outer ectoderm, middle mesoderm, and inner endoderm. These germ layers subsequently give rise to all tissues and organs in adults. The inner cells are also known as stem cells, possessing the potency to develop into various tissues and organs. Human pregnancy typically lasts 9 lunar months (approximately 280 days). The fetal heart develops within the first month. Early signs of fetal growth, such as heartbeats, can be detected via stethoscope. By the end of the second month, the fetus develops limbs and digits. Most major organs (limbs and external genital organs) are formed by the completion of 3 months (first trimester). The intrauterine period is termed gestation. Fetal movements and hair appearance on the head are usually observed by the 5th month. By 24 weeks (second trimester), the body is covered with fine hair, eyelids separate, and eyelashes form. At the end of nine months, the fetus is fully developed and prepared for delivery.

In simple words: After implantation, the placenta forms, connecting mother and fetus for nutrient exchange and waste removal, while also producing hormones for pregnancy. The embryo develops germ layers into organs, and the fetus grows and matures over nine months until birth, regulated by various hormones.

🎯 Exam Tip: Focus on the placenta's dual role (exchange and endocrine), the three germ layers and their broad derivatives, and the key developmental milestones during each trimester of pregnancy.

 

Question 36.
'A fertilised egg is a blue print for future development'. Justify the statement.

Answer:
After fertilization, the fertilized egg (zygote) undergoes repeated cell division, a process known as cleavage, to form smaller cells called blastomeres. Through successive cleavage divisions, the zygote transforms into a solid ball of cells resembling a mulberry, termed a morula. The morula then develops into a blastula, and subsequently into a gastrula. Up to the morula stage, the cells are undifferentiated. However, after this stage, the cells begin to differentiate and specialize, forming various organs. Therefore, a fertilized egg is aptly described as a blueprint for future development, as it contains all the genetic instructions and developmental potential to guide the formation of an entire organism.

In simple words: A fertilized egg contains all the genetic information and developmental instructions, acting as a "blueprint" that guides cell division, differentiation, and organ formation to create a complete organism.

🎯 Exam Tip: The key to justifying this statement is to link the fertilized egg's genetic material to the processes of cleavage, differentiation, and organ formation, showing how it contains the complete plan for development.

 

Question 37.
Amnion is an effective shock absorber. Comment on it.

Answer:
The amnion encloses the embryo in a fluid-filled medium (amniotic fluid). This fluid acts as a cushion, protecting the developing embryo from mechanical shocks and physical trauma. Furthermore, it prevents the embryo from desiccation (drying out), thus efficiently serving as a shock absorber and protective environment.

In simple words: The amnion surrounds the embryo with amniotic fluid, which acts like a protective cushion, absorbing impacts and preventing the embryo from drying out.

🎯 Exam Tip: Emphasize both functions: shock absorption (mechanical protection) and prevention of desiccation, to fully explain the amnion's role as a protective structure.

 

Question 38.
First trimester of pregnancy is critical. Give reason.

Answer:
The first three months (first trimester) of pregnancy are considered critical because this is the period when most of the major organ systems of the fetus develop (organogenesis). After the third month, development primarily involves growth and structural maturation, rather than the formation of new organs. Consequently, utmost care and caution are essential during the first trimester to ensure proper fetal development and minimize risks.

In simple words: The first trimester is critical because all major organs are forming rapidly, making the fetus highly vulnerable to damage during this crucial developmental period.

🎯 Exam Tip: The critical nature of the first trimester stems from organogenesis; link this period to major organ formation and increased vulnerability for a strong answer.

 

Question 39.
Find the odd one out in each group and justify.
a. Vasa efferentia, epididymis, prostate gland, seminal vesicle, fallopian
b. Ovary, penis, vagina, uterus, oviduct
c. Proliferative phase, menstrual phase, multiplication phase, ovulatory phase, secretory phase.
d. Budding, gametogenesis, fertilization, cleavage, gastrulation
e. Acrosome, zona pellucida, distal centriole, middle piece, axial centriole
f. Amnion, foetus, chorion, allantois, yolk sac

Answer:
a. **fallopian tube** (Justification: All others are components of the male reproductive system or accessory glands, while the fallopian tube is part of the female reproductive system.)
b. **penis** (Justification: All others are components of the female reproductive system, whereas the penis is part of the male reproductive system.)
c. **multiplication phase** (Justification: All others are phases of the menstrual cycle, while the multiplication phase is a stage in gametogenesis.)
d. **budding** (Justification: All others are processes involved in sexual reproduction and embryonic development in humans, while budding is a form of asexual reproduction.)
e. **zona pellucida** (Justification: All others are structural components of a sperm, while the zona pellucida is an outer membrane of the ovum.)
f. **foetus** (Justification: All others are extraembryonic membranes that surround and support the fetus, whereas the fetus is the developing organism itself.)

In simple words: The odd ones out are: fallopian tube (female structure in male group), penis (male structure in female group), multiplication phase (gametogenesis phase in menstrual cycle group), budding (asexual reproduction in sexual development group), zona pellucida (egg part in sperm part group), and fetus (organism itself among supporting membranes).

🎯 Exam Tip: To identify the odd one out, classify each item in the list by its biological system, reproductive process, or structure. The one that doesn't fit the category is the correct answer, and your justification should clearly state why.

 

Question 40.
Observe the diagram.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मासिक धर्म चक्र (Menstrual Cycle) के हार्मोनल और गर्भाशय संबंधी परिवर्तनों को दर्शाता है। यह पिट्यूटरी हार्मोन (FSH, LH) और डिम्बग्रंथि हार्मोन (एस्ट्रोजन, प्रोजेस्टेरोन) के स्तर में उतार-चढ़ाव, डिम्बग्रंथि की घटनाओं (फॉलिकल विकास, ओव्यूलेशन, कॉर्पस ल्यूटियम का निर्माण), और गर्भाशय की घटनाओं (मासिक धर्म, प्रोलिफेरेटिव चरण, स्रावी चरण) को दर्शाता है। यह प्रजनन जीवन चक्र के महत्वपूर्ण चरणों और उनकी परस्पर निर्भरता को रेखांकित करता है।
Answer:
a. This event takes place in the Ovary and Uterus.
b. The menstrual cycle comprises the following phases in sequence from day one to twenty-eight:
* **Menstrual phase:** (Day 1-5) Characterized by menstrual bleeding.
* **Follicular (Proliferative) phase:** (Day 5-15) During this phase, the endometrium regenerates and proliferates, and an egg travels to the fallopian tube.
* **Ovulatory phase:** (Around Day 14) Ovulation occurs, where the mature ovum is released from the ovary.
* **Luteal (Secretory) phase:** (Day 16-28) The endometrium continues to thicken and becomes secretory, preparing for possible implantation.
The rhythmic series of changes occurring in the sex organs approximately every 28 days throughout a human female's reproductive life (from puberty to menopause) is termed the menstrual cycle. This cycle is absent during pregnancy and may be suppressed during lactation.
In a typical woman, ovulation happens on the 14th day after menstruation. If the ovum is not fertilized, the endometrium breaks down, leading to bleeding (menstruation or menses). During this time, the female reproductive organs undergo a series of changes, influencing sexual behavior. The menstrual cycle combines the ovarian cycle (events leading to ovulation and corpus luteum development) and the uterine cycle (cyclic changes in the uterine wall that thickens before ovulation and sheds if fertilization doesn't occur).
c. The hormones involved in this event are FSH, Estrogens, LH, and Progesterone.

In simple words: The menstrual cycle, occurring in the ovary and uterus, involves menstrual, follicular, ovulatory, and luteal phases, regulated by FSH, LH, estrogen, and progesterone. It prepares the body for potential pregnancy and ceases upon fertilization or during menopause.

🎯 Exam Tip: When describing the menstrual cycle, detail each phase, its approximate duration, the key ovarian and uterine events, and the specific hormones regulating each stage for a comprehensive answer.

 

Question 41. Change in nucleus, acrosome formation, changes in mitochondria, cen- trioles, cytoplasm. These events take place in a reproductive system. a. In which reproductive system do these events take place? b. Why do these changes take place?
Answer:
a. These events occur in the male reproductive system.
b. These transformations occur to convert a spermatid into a fully functional and mature sperm.In simple words: These changes are essential to transform immature sperm cells into mature, mobile sperm capable of fertilization.

🎯 Exam Tip: Understanding the structural modifications of sperm during spermiogenesis is crucial for explaining male fertility and reproductive processes.

 

Question 42. The relaxin secreted by placenta relaxes the pubic ligaments during parturition. i. Mention the other hormones secreted by placenta. ii. Suppose relaxin is not secreted, mention the other method for the delivery of the child.
Answer:
i. The placenta secretes several other hormones, including Human Chorionic Gonadotropin (hCG), chorionic thyrotropin, chorionic corticotropin, human placental lactogen (hPL), estrogens, and progesterone.
ii. If relaxin is not secreted, preventing the relaxation of pubic ligaments, a Caesarean section (C-section) would be the alternative method for childbirth.In simple words: The placenta produces hormones vital for pregnancy; if relaxin isn't produced, leading to rigid pubic ligaments, a C-section is required for delivery.

🎯 Exam Tip: Knowing the functions of key placental hormones and their role in facilitating a natural birth or indicating the need for medical intervention is important.

 

Question 14. a. Observe and name the hormones A, B, C and D
b. Copy the flow chart and represent the feed back mechanism in that.
Answer:
a. The hormones are identified as: A represents Follicle-Stimulating Hormone (FSH), B represents Luteinizing Hormone (LH), C denotes Estrogen, and D signifies Progesterone.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख शुक्राणुजनन के हार्मोनल नियंत्रण को दर्शाता है। इसमें हाइपोथैलेमस से GnRH का स्राव होता है, जो अग्र पिट्यूटरी को FSH और LH (जिसे A और B कहा गया है) जारी करने के लिए उत्तेजित करता है। LH (B) Leydig कोशिकाओं को टेस्टोस्टेरोन स्रावित करने के लिए प्रेरित करता है, जो शुक्राणुजनन और अन्य प्रजनन अंगों को प्रभावित करता है। FSH (A) Sertoli कोशिकाओं को उत्तेजित करता है, जो हार्मोन इन्हीबिन स्रावित करती हैं। टेस्टोस्टेरोन GnRH और LH उत्पादन को रोककर नकारात्मक प्रतिक्रिया प्रदान करता है।

ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख अंडाणुजनन के हार्मोनल नियंत्रण को दर्शाता है। हाइपोथैलेमस से GnRH अग्र पिट्यूटरी को FSH और LH (जिसे A और B कहा गया है) जारी करने के लिए उत्तेजित करता है। FSH और LH अंडाशय को एस्ट्रोजन (C) और प्रोजेस्टेरोन (D) स्रावित करने के लिए प्रेरित करते हैं, जो गर्भाशय को प्रभावित करते हैं। अंडाशय से एस्ट्रोजन और प्रोजेस्टेरोन का उत्पादन GnRH, FSH और LH पर नकारात्मक प्रतिक्रिया देता है, जबकि एस्ट्रोजन का उच्च स्तर GnRH पर सकारात्मक प्रतिक्रिया दे सकता है।In simple words: This question asks to identify the key hormones involved in regulating both sperm production (spermatogenesis) and egg production (oogenesis), and to illustrate the feedback mechanisms in oogenesis. FSH and LH from the pituitary gland control these processes, with sex hormones like testosterone, estrogen, and progesterone providing feedback to maintain balance.

🎯 Exam Tip: Memorizing the hormonal pathways and feedback loops for both male and female reproductive systems is crucial for high scores in reproductive biology questions.

 

Question 44. The diagram of human blastocyst is given below. A -B (Blastocyst) a. Identify A and B b. Mention the fate of 'B' c. Copy and fill the given flow chart showing the fate of A
Answer:
a. Part A is identified as the inner cell mass, and part B is the trophoblast.
b. The trophoblast (B) ultimately develops into the placenta, which is crucial for nutrient and waste exchange.
c. The flowchart showing the fate of A (Inner cell mass) is as follows:

Germ Layer (Derived from Inner Cell Mass)	Derived Organs/Systems
Ectoderm	Nervous System, skin, hair, nails, sensory organs, pituitary gland, adrenal medulla
Mesoderm	Muscles, bones, connective tissue, circulatory system, excretory system, reproductive system, dermis of skin, adrenal cortex
Endoderm	Lining of digestive tract, respiratory tract, liver, pancreas, urinary bladder, thyroid gland, parathyroid glands, thymus

In simple words: A blastocyst has two main parts: the inner cell mass (A) that forms the embryo and its germ layers, and the trophoblast (B) that develops into the placenta.

🎯 Exam Tip: Knowing the key structures of a blastocyst and the developmental fate of the inner cell mass (germ layers) and trophoblast is fundamental for embryology questions.

 

Question 45. A concept map showing the filtration between glomerulus and Bowman's capsule is given below. Draw a concept map to show the filtration between uterine wall and placenta.
Answer: A concept map illustrating the filtration process between the uterine wall and the placenta would highlight the exchange of substances. Oxygen and nutrients (like glucose, amino acids, vitamins, minerals) from the maternal blood pass to the fetal blood, while carbon dioxide and metabolic waste products (like urea) from the fetal blood pass to the maternal blood for excretion. This bidirectional exchange ensures fetal sustenance and waste removal.In simple words: The placenta acts as a filter, allowing oxygen and nutrients to pass from mother to fetus, and waste products from fetus to mother, similar to how the kidney filters blood.

🎯 Exam Tip: Understanding the analogy between glomerular filtration and placental exchange mechanisms can help clarify the vital functions of both organs in maintaining homeostasis.

 

Question 46. a. When and where does spermatogenesis in a human male begin to take place? b. With the help of schematic labelled diagrams, trace the development of mature spermatozoa in a human male? c. Describe the structure of a human sperm.
Answer:
a. In human males, spermatogenesis, the process of sperm production from immature germ cells (spermatogonia), commences in the testes at the onset of puberty.
b.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख मानव शुक्राणुजनन की प्रक्रिया को दर्शाता है, जो यौवनारंभ में शुरू होती है। इसमें शुक्राणुजन (spermatogonia) सूत्रीविभाजन और विभेदन से गुजरते हुए प्राथमिक शुक्राणुकोशिका (primary spermatocytes) बनाते हैं। प्राथमिक शुक्राणुकोशिकाएँ प्रथम अर्धसूत्रीविभाजन द्वारा द्वितीयक शुक्राणुकोशिका (secondary spermatocytes) बनाती हैं, जो द्वितीय अर्धसूत्रीविभाजन से गुजरकर शुक्राणुपुत्र (spermatids) बनाती हैं। अंत में, शुक्राणुपुत्र विभेदन द्वारा परिपक्व शुक्राणु (spermatozoa) में परिवर्तित हो जाते हैं।
c. The human sperm is structurally divided into three main parts: a head, a neck, a middle piece, and a tail. A plasma membrane encloses the entire sperm body. The anterior region of the head is covered by an acrosome, a cap-like structure containing enzymes vital for fertilizing the ovum. The middle piece is characterized by numerous mitochondria, which generate the energy required for the tail's movement, facilitating sperm motility crucial for fertilization.In simple words: Spermatogenesis starts in the testes at puberty, transforming germ cells into mature sperm. Each sperm has a head (with acrosome), neck, middle piece (for energy), and a tail (for movement).

🎯 Exam Tip: A clear understanding of the stages of spermatogenesis and the detailed structure of a sperm is essential for describing male reproductive biology.

 

Question 47. The two diagrams showing the events in oogenesis and spermatogenesis are represented below. Answer the questions following the diagram. i. State the levels of FSH, LH and progesterone simply by mentioning high or low, around 13-th and 14-th day and 21st to 23rd day. ii. In which of the above mentioned phases does the egg travel to the fallopian tube? iii. Why is there no menstruation upon fertilisation?
Answer:
i. Around days 13-14 of the cycle, Luteinizing Hormone (LH) levels are high, while Follicle-Stimulating Hormone (FSH) levels are low. However, during days 21-23, both FSH and LH levels are observed to be low.
ii. During the proliferative or follicular phase, the ovum traverses through the fallopian tube.
iii. Menstruation does not occur after fertilization because the menstrual cycle stops, allowing the pregnancy to establish. In the absence of fertilization, the corpus luteum degenerates, causing a new menstrual cycle to begin. This distinction is important, as menopause refers to the permanent cessation of menstruation, not the temporary halt during pregnancy.In simple words: This question examines the hormonal fluctuations during the menstrual cycle, the journey of the egg, and why menstruation stops if fertilization occurs to allow for pregnancy.

🎯 Exam Tip: Accurately recalling the hormonal levels and events of each phase of the menstrual cycle, especially around ovulation and post-fertilization, is vital for questions on female reproduction.

 

Question 48. At what stage of life is oogenesis initiated in a human female? When does the oocyte complete oogenesis?
Answer: Oogenesis in human females begins during the fetal stage, with primary oocytes forming before birth. These primary oocytes then remain arrested in prophase-I of meiosis until puberty. The process of oogenesis is completed when the oocyte matures into a Graafian follicle and is released, or upon fertilization.In simple words: Egg formation starts before birth but is paused until puberty, completing only when the egg matures and is released or fertilized.

🎯 Exam Tip: Highlighting the prenatal initiation and two-stage completion of oogenesis, distinguishing it from spermatogenesis, is key for scoring well.

 

Question 49. Given below is an incomplete flow chart showing influence of hormones on gametogenesis in males. Observe the flow chart carefully and fill in the blanks A, B, C and D
Answer: Upon observing the incomplete flowchart for hormonal regulation of male gametogenesis, the identified blanks are:
A – The hormone secreted by Leydig cells is **Testosterone**.
B – The process influenced by testosterone is **Spermatogenesis**.
C – The cells stimulated by FSH are **Sertoli cells**.
D – The process stimulated by factors from Sertoli cells is **Spermiogenesis**.In simple words: This flowchart explains how pituitary hormones (ICSH/LH and FSH) control sperm production in males by stimulating Leydig cells to produce testosterone and Sertoli cells to support spermiogenesis.

🎯 Exam Tip: Correctly identifying the hormones, cells, and processes in the male gametogenesis flowchart demonstrates a strong grasp of endocrine control in reproduction.

 

Question 50. a. In which part of the human female reproductive system do the following events take place?
I - Release of 1st polar body.
II – Release of 2nd polar body
III - Fertilisation
IV - Implantation
b. From where do signals for parturition originate and what does maternal pituitary release for stimulating uterine concentrations for child birth?
Answer:
a. The locations for these events in the human female reproductive system are:
I - The first polar body is typically released in the **ovary** (specifically within the Graafian follicle just before ovulation, during meiosis I completion).
II – The second polar body is released in the **fallopian tube** (specifically after fertilization occurs).
III - Fertilization occurs in the **fallopian tube** (ampullary-isthmic junction).
IV - Implantation takes place in the **uterus** (endometrium).
b. Signals initiating parturition originate from the fully developed fetus and the placenta. This triggers the maternal pituitary gland to release oxytocin, a hormone that stimulates robust uterine contractions, facilitating childbirth.In simple words: This question asks about key events in female reproduction-egg development, fertilization, and pregnancy initiation-and how childbirth is triggered by fetal and placental signals, leading to oxytocin release.

🎯 Exam Tip: Precisely locating each event (polar body release, fertilization, implantation) and understanding the neuro-hormonal control of parturition are critical for detailed answers.

 

Question 51. Show diagrammatically the stages of embryonic development from zygote upto implantation in humans.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख मानव में युग्मनज से आरोपण तक भ्रूण के विकास के चरणों को दर्शाता है। निषेचन के बाद, युग्मनज क्रमिक रूप से विभाजित होता है, जिससे 2-कोशिका, 4-कोशिका और 8-कोशिका अवस्थाएँ बनती हैं। फिर यह एक ठोस कोशिका द्रव्यमान, मोरूला में विकसित होता है, जिसके बाद एक गुहा बनती है, जिससे ब्लास्टोसिस्ट बनता है। ब्लास्टोसिस्ट की बाहरी परत को ट्रोफोब्लास्ट कहा जाता है, और आंतरिक कोशिका द्रव्यमान से भ्रूण बनता है, अंततः गर्भाशय की एंडोमेट्रियम में आरोपण होता है। The developmental process begins with the fusion of haploid sperm and ovum nuclei, forming a diploid zygote. This zygote then undergoes a series of rapid mitotic divisions, known as cleavage, to form structures like the 2-cell, 4-cell, and 8-cell stages. Continued cleavage leads to a solid mass of 16 cells called a morula. Subsequently, the morula develops a fluid-filled cavity, transforming into a blastocyst, which consists of an outer trophoblast layer and an inner cell mass. This blastocyst then embeds itself into the uterine endometrium, a process termed implantation, which marks the initiation of pregnancy.In simple words: After fertilization, the single-celled zygote repeatedly divides to form a ball of cells (morula), then a hollow structure (blastocyst), which finally implants itself into the uterus to start pregnancy.

🎯 Exam Tip: Accurately drawing and labeling the sequence from zygote to blastocyst and describing each stage's significance for implantation is essential for embryology questions.