CBSE Class 9 Science Exemplar Chapter 12: Why Do We Fall Ill? NCERT Solutions
This chapter delves into the fundamental concepts of health and disease, crucial for Class 9 Science students. The NCERT Solutions for Chapter 12, 'Why Do We Fall Ill?', provide clear explanations and answers to various questions, including multiple-choice ones. It covers the different types of diseases, their causes (viral, bacterial, protozoan), modes of transmission (like mosquito bites or contaminated food/water), and the distinction between acute and chronic illnesses. The solutions also highlight the long-term health impacts of habits like chewing tobacco and differentiate between communicable and non-communicable conditions. These detailed solutions are designed to help students grasp the core principles of health and disease, aiding in their exam preparation and fostering a better understanding of personal well-being.
Quick info
| Board | CBSE |
|---|---|
| Class | Class 9 |
| Subject | Science Exemplar |
| Session | 2026 |
| Language | English |
| Type | NCERT Solutions |
| Chapter | Chapter 12 |
Chapter summary
Chapter 12 of the Class 9 Science Exemplar, 'Why Do We Fall Ill?', focuses on understanding the causes, types, and transmission of diseases. The NCERT Solutions cover key concepts such as viral, bacterial, and protozoan infections, mosquito-borne illnesses, and diseases spread through contaminated food and water. It also distinguishes between acute and chronic diseases and discusses the long-term health consequences of certain habits. These solutions offer a comprehensive review of the chapter's content, reinforcing learning for students.
Learning outcomes
- Identify different types of diseases and their causative agents.
- Differentiate between viral, bacterial, and protozoan diseases.
- Understand the modes of disease transmission, including vectors like mosquitoes.
- Distinguish between acute and chronic diseases.
- Recognize the long-term health effects of unhealthy habits.
- Explain how diseases spread through contact with infected individuals.
Topics covered
Paper topics
- Health and Disease
- Types of Diseases
- Causes of Diseases
- Viral Diseases
- Bacterial Diseases
- Protozoan Diseases
- Disease Transmission
- Mosquito-borne Diseases
- Acute vs. Chronic Diseases
- Long-term Health Effects
- Communicable Diseases
- Non-communicable Diseases
Important topics
- Distinguishing between different types of diseases (viral, bacterial, protozoan)
- Understanding disease transmission routes
- Identifying mosquito-borne illnesses
- Recognizing the impact of lifestyle choices on long-term health
- Differentiating acute and chronic health conditions
PDF preview
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Questions and Solutions
Multiple Choice Questions
Dengue
AIDS
Typhoid
Influenza
Typhoid is a bacterial infection caused by the bacterium Salmonella typhi. Dengue, AIDS, and Influenza are all caused by viruses.
Cholera
Tuberculosis
Anthrax
Influenza
Cholera is caused by Vibrio cholerae, Tuberculosis by Mycobacterium tuberculosis, and Anthrax by Bacillus anthracis. All these are bacteria. Influenza, however, is caused by the influenza virus.
Brain fever
Malaria
Typhoid
Dengue
Typhoid is primarily transmitted through contaminated food and water, not by mosquito bites. Brain fever (encephalitis), Malaria, and Dengue are all transmitted by mosquitoes.
Typhoid
Anthrax
Tuberculosis
Malaria
Malaria is caused by protozoans of the genus Plasmodium, such as Plasmodium vivax. Typhoid, Anthrax, and Tuberculosis are all diseases caused by bacteria.
Malaria
Influenza
AIDS
Cholera
Malaria is caused by protozoan parasites, specifically Plasmodium species. Influenza is viral, AIDS is caused by a virus (HIV), and Cholera is bacterial.
Common cold
Chicken pox
Chewing tobacco
Stress
Common cold and chickenpox are acute diseases that resolve relatively quickly without long-term health consequences. While stress can be detrimental, it is often manageable. Chewing tobacco, however, is a habit that can lead to severe long-term health problems, including various cancers and cardiovascular diseases.
High blood pressure
Genetic abnormalities
Sneezing
Blood cancer
Sneezing is a symptom of infectious diseases (like the common cold or flu) and can spread pathogens to others through respiratory droplets. High blood pressure and genetic abnormalities are not typically spread through contact. Blood cancer is not generally considered communicable through casual contact.
Common mistakes
- Confusing the causative agents of diseases (e.g., bacteria vs. viruses).
- Incorrectly identifying diseases transmitted by mosquitoes.
- Failing to distinguish between acute and chronic health issues.
- Underestimating the long-term impact of habits like tobacco use.
Revision tips
- Create flashcards for diseases, their causes, and transmission methods.
- Draw diagrams illustrating disease transmission cycles.
- Focus on understanding the difference between acute and chronic illnesses.
- Review the long-term health effects of lifestyle choices discussed in the chapter.
Practice MCQs
Q1. Which of the following diseases is NOT caused by a virus?
Explanation: Typhoid is a bacterial infection caused by Salmonella Typhi, while Dengue, AIDS, and Influenza are viral diseases.
Q2. Influenza is an example of which type of disease?
Explanation: Influenza is caused by the influenza virus, making it a viral disease.
Q3. Which of these diseases is transmitted through contaminated food and water, and NOT by mosquitoes?
Explanation: Typhoid is primarily spread through contaminated food and water, unlike Malaria, Dengue, and Brain fever which are mosquito-borne.
Q4. Malaria is caused by which type of microorganism?
Explanation: Malaria is caused by protozoans of the genus Plasmodium, such as Plasmodium vivax.
Q5. Which of the following conditions has a significant long-term negative effect on health?
Explanation: Chewing tobacco is known to cause chronic health problems like cancer, whereas common cold, chickenpox, and manageable stress are typically acute or temporary.
Q6. Which disease is NOT caused by bacteria?
Explanation: Malaria is caused by protozoans. Cholera, Tuberculosis, and Anthrax are all bacterial diseases.
Frequently asked questions
What is the main focus of Chapter 12, 'Why Do We Fall Ill?' for Class 9 Science?
This chapter focuses on understanding the fundamental concepts of health and disease, including the various causes, types, transmission methods, and prevention strategies for common illnesses.
What are the different categories of diseases discussed in these NCERT Solutions?
The solutions cover diseases caused by viruses, bacteria, and protozoans, as well as differentiating between acute and chronic diseases and those transmitted by vectors like mosquitoes.
How do these NCERT Solutions help in exam preparation?
These solutions provide clear, rewritten answers to all questions, explaining the concepts thoroughly and reinforcing understanding, which is essential for effective exam revision.
Are the questions in the source document preserved in these solutions?
Yes, all questions from the source document are kept exactly the same in terms of numbering and the problem asked. The wording has been expanded for clarity where needed.
What is the difference between an acute and a chronic disease as explained in the solutions?
Acute diseases are short-term illnesses with no long-term health effects, like the common cold. Chronic diseases have long-term effects on health, such as those caused by habits like chewing tobacco.
Which diseases are mentioned as being transmitted by mosquitoes?
The solutions mention diseases like Dengue, Malaria, and Brain fever as being transmitted by mosquitoes.
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