Step-by-Step Solutions For Class 8 Science Chapter 9 In Hindi - Free PDF Download
1. जीवों में प्रजनन के महत्व की व्याख्या करें।
उत्तर: प्रजनन इस ग्रह पृथ्वी पर एक महत्वपूर्ण घटना है जो अस्तित्व और जीवन और प्रजातियों की निरंतरता, पीढ़ी दर पीढ़ी के लिए आवश्यक है।
2. मनुष्य में निषेचन की प्रक्रिया का वर्णन कीजिए।
उत्तर: निषेचन की प्रक्रिया में, शुक्राणु एक अंडाणु (अंडे) के संपर्क में आते हैं। शुक्राणुओं में से एक अंडे के साथ विलीन हो सकता है। शुक्राणु और अंडाणु के केंद्रक मिलकर एक एकल नाभिक बनाते हैं जिसके परिणामस्वरूप एक निषेचित अंडे का निर्माण होता है जिसे युग्मनज कहा जाता है। मानव में, निषेचन महिला के शरीर के अंदर होता है, जिसे आंतरिक निषेचन के रूप में जाना जाता है।
3. सबसे उपयुक्त उत्तर चुनें।
(ए) आंतरिक निषेचन होता है
(i) महिला शरीर में।
(ii) महिला शरीर के बाहर।
(iii) पुरुष शरीर में।
(iv) पुरुष शरीर के बाहर।
उत्तर: (i) महिला शरीर में।
(बी) एक टैडपोल की प्रक्रिया द्वारा एक वयस्क मेंढक में विकसित होता है:
(i) निषेचन
(ii) कायापलट
(iii) एम्बेडिंग
(iv) नवोदित
उत्तर: (ii) कायापलट
(सी) एक युग्मनज में मौजूद नाभिक की संख्या है:
(i) कोई नहीं
(ii) एक
(iii) दो
(iv) चार
उत्तर: (ii) एक
4. संकेत दें कि निम्नलिखित कथन सत्य $({\text{T}})$ हैं या असत्य \[\left( {\text{F}} \right)\]।
1. ओविपेरस जानवर बच्चों को जन्म देते हैं।
उत्तर: असत्य
2. प्रत्येक शुक्राणु एक एकल कोशिका है।
उत्तर: सत्य
3. मेंढक में बाह्य निषेचन होता है।
उत्तर: सत्य
4. एक नया मानव व्यक्ति युग्मक नामक कोशिका से विकसित होता है।
उत्तर: असत्य
5. निषेचन के बाद दिया गया अंडा एक ही कोशिका से बना होता है।
उत्तर: सत्य
6. अमीबा नवोदित होकर प्रजनन करता है।
उत्तर: असत्य
7. अलैंगिक जनन में भी निषेचन आवश्यक है।
उत्तर: सत्य
8. बाइनरी विखंडन अलैंगिक प्रजनन की एक विधि है।
उत्तर: सत्य
9. निषेचन के परिणामस्वरूप युग्मनज बनता है।
उत्तर: सत्य
10. भ्रूण एक एकल कोशिका से बना होता है।
उत्तर: असत्य
5. युग्मनज और भ्रूण में दो अंतर बताइए।
उत्तर:
6. अलैंगिक जनन को परिभाषित कीजिए। जंतुओं में अलैंगिक जनन की दो विधियों का वर्णन कीजिए।
उत्तर: जनन की वह विधि जिसमें केवल एक ही जनक शामिल होता है, अलैंगिक जनन कहलाता है। इस प्रकार के प्रजनन में, सेक्स कोशिकाओं (युग्मक) का उत्पादन नहीं होता है और युग्मनज या संतानों के प्रजनन के लिए युग्मकों का कोई संलयन नहीं होता है। अलैंगिक प्रजनन अमीबा, हाइड्रा, खमीर, तारामछली, स्पंज आदि में होता है।
अलैंगिक प्रजनन के मुख्य रूप से दो तरीके हैं:
(i) बाइनरी विखंडन: बाइनरी विखंडन में, एक एकल मूल कोशिका अमीबा की तरह दो समान व्यक्तिगत कोशिकाओं में विभाजित होती है। यह उनके शरीरों को विभाजित करके दो में विभाजित हो जाता है, उनमें से प्रत्येक को एक नाभिक मिलता है और अलग-अलग व्यक्ति में विकसित होता है।
(ii) बडिंग: नवोदित में, जीव कली नामक एक उभार विकसित करता है जो आगे एक वयस्क जीव में विकसित होता है और एक स्वतंत्र जीवन जीने के लिए खुद को मूल शरीर से अलग करता है। इस प्रकार का प्रजनन हाइड्रा में दिखाया गया है। निम्नलिखित आंकड़ा हाइड्रा में नवोदित दिखाता है।
7. भ्रूण किस मादा प्रजनन अंग में अंतःस्थापित होता है?
उत्तर: गर्भाशय
8. कायापलट क्या है? उदाहरण दो।
उत्तर: एक अकशेरुकी या उभयचर के जीवन चक्र के दौरान एक जानवर के शरीर में अचानक और अचानक परिवर्तन से जुड़े लार्वा के वयस्क में परिवर्तन को कायापलट कहा जाता है। उदाहरण, मेंढक और तितली।
9. आंतरिक निषेचन और बाह्य निषेचन में अंतर स्पष्ट कीजिए।
उत्तर:
10. नीचे दिए गए संकेतों का प्रयोग कर वर्ग पहेली को पूरा कीजिए।
पार
1. युग्मकों के संलयन की प्रक्रिया।
6. मुर्गी में निषेचन का प्रकार।
7. हाइड्रा के शरीर के किनारों पर देखे गए उभार के लिए इस्तेमाल किया जाने वाला शब्द।
8. यहां अंडे का उत्पादन होता है।
डाउन
2. इन पुरुष प्रजनन अंगों में शुक्राणु उत्पन्न होते हैं।
3. निषेचित अंडे के लिए एक और शब्द।
4. ये जानवर अंडे देते हैं।
5. अमीबा में एक प्रकार का विखंडन।
उत्तर:
NCERT Solutions for Class 8 Science Chapter 9 Reproduction in Animals in Hindi
Chapter-wise NCERT Solutions are provided everywhere on the internet with an aim to help the students to gain a comprehensive understanding. Class 8 Science Chapter 9 solution Hindi medium is created by our in-house experts keeping the understanding ability of all types of candidates in mind. NCERT textbooks and solutions are built to give a strong foundation to every concept. These NCERT Solutions for Class 8 Science Chapter 9 in Hindi ensure a smooth understanding of all the concepts including the advanced concepts covered in the textbook.
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NCERT Solutions in Hindi medium have been created keeping those students in mind who are studying in a Hindi medium school. These NCERT Solutions for Class 8 Science Reproduction in Animals in Hindi medium pdf download have innumerable benefits as these are created in simple and easy-to-understand language. The best feature of these solutions is a free download option. Students of Class 8 can download these solutions at any time as per their convenience for self-study purpose.
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FAQs on NCERT Solutions For Class 8 Science Chapter 9 Reproduction In Animals in Hindi - 2025-26
1. Does friction only happen when an object is moving?
No, friction also acts on stationary objects; this is called static friction. It's the force you must overcome to start moving something, like pushing a heavy desk. Static friction is what prevents a book from sliding down a tilted table.
2. Does using the friction Class 8 NCERT Solutions PDF mean I'm not learning?
No, using the friction Class 8 NCERT Solutions PDF effectively is a smart study technique, not a shortcut. The common myth is that looking at a solution is cheating, but its real purpose is to guide and verify your own work.
The best method is to attempt all the friction class 8 questions and answers on your own first. After completing a problem, use the solutions to check your steps and final answer. This helps you pinpoint exactly where you made a mistake—for instance, maybe you confused static and sliding friction in an explanation.
This active self-checking process reinforces concepts and builds confidence. You aren't just getting the answer; you are learning the correct method to arrive at it, which is crucial for exams.
Think of solutions as a tool for self-assessment, not a substitute for effort.
3. Is friction always a bad or unhelpful force?
No, friction is often a necessary and helpful force. While it does cause wear and produces unwanted heat, we depend on it to walk without slipping, write on paper, and for car brakes to work. Many everyday actions would be impossible without it.
4. Is it true that a perfectly smooth surface has zero friction?
No, even a surface that appears perfectly smooth still has friction. This misconception occurs because we associate friction with obvious roughness, but on a microscopic level, all surfaces have tiny imperfections like hills and valleys called irregularities.
When two surfaces, like a glass slab and a wooden block, are in contact, these micro-level irregularities interlock. To make one surface slide over the other, you must apply force to break these interlocks. This resistance to movement is friction. This is why even a rolling ball on a polished floor eventually stops.
The NCERT Chapter 9 explains that friction is caused by the interlocking of irregularities on the two surfaces in contact. Greater smoothness reduces this interlocking, but it never eliminates it completely.
So, smoothness reduces friction but never makes it zero.
5. Do the NCERT solutions just give the final answer for each question?
No, a quality NCERT solution for class 8 science chapter 9 provides detailed, step-by-step explanations for every question. They are designed to show the correct scientific reasoning and method, not just the final result, helping you learn how to solve problems yourself.
6. Are the NCERT Solutions PDFs only for the end-of-chapter exercise questions?
No, comprehensive NCERT Solutions for Class 8 Science Chapter 9 cover more than just the final exercise questions. A common misunderstanding is that solutions are only for the list of questions at the very end of the chapter.
Well-structured solutions, like those in the Vedantu Free PDF, also often include explanations for in-text questions and activities mentioned within the chapter. This ensures you understand the concepts as they are introduced, not just during the final review. For example, it will explain the 'why' behind activities like observing the effect of a lubricant on a carrom board.
By covering all types of questions, these resources provide a complete picture of the chapter's content, ensuring no concept is missed.
This holistic approach helps build a stronger foundation for the entire chapter.
7. Is rolling friction stronger than sliding friction?
No, rolling friction is actually much weaker than sliding friction. This is why it is easier to roll a heavy suitcase with wheels than to drag it across the floor. The wheels reduce the contact area and the interlocking of surfaces.
8. Does friction only depend on the type of surface, like wood or glass?
No, the force of friction depends on two main factors: the nature of the surfaces in contact and how hard they are pressed together. The myth is that only the material's roughness matters.
While the type of surface is important (e.g., rubber on concrete has more friction than steel on ice), the force pressing them together (the normal force) is equally critical. For example, it is much harder to push a heavy box than an empty one across the same floor. The heavy box presses down with more force, increasing the interlocking of surface irregularities and thus increasing friction.
So, remember the rule: Friction depends on both the coefficient of friction (surface nature) and the normal force (how hard surfaces are pressed).
Both surface nature and pressing force determine the amount of friction.
9. Do I have to pay to get the friction class 8 NCERT PDF?
No, you can typically access the friction class 8 ncert pdf for solutions for free. Reputable educational platforms provide these resources as a Free PDF download to help students study effectively without any cost, allowing for easy offline access on any device.
10. Are all questions in the Class 8 Science Chapter 9 question answer section equally important?
NCERT Solutions for Class 8 Science Chapter 9 are designed to cover the entire syllabus, but some question types are more frequently asked in exams. It's a myth that you should focus on just one type, like definitions, and ignore others.
A balanced approach is best. Pay close attention to questions that ask you to "explain why," as these test your conceptual understanding of friction (e.g., why athletes use shoes with spikes). Also, focus on questions that differentiate between types of friction (static, sliding, rolling) and those that discuss methods to increase or reduce it.
While every class 8 science chapter 9 question answer helps build your knowledge, prioritize those that test application and reasoning. The solutions help by showing you how to structure these high-value answers correctly.
Use solutions to master concept-based and 'why' questions for better exam preparation.
